Power Consultants & Agencies Page 1 TRAINING SESSIONS ON CONSTRUCTION, PLANNING & DESIGN OF EHV TRANSMISSION LINES BY S. M. TAKALKAR PROPRIETOR POWER CONSULTANTS & AGENCIES A / 198 VISHVAMITRY TOWNSHIP, OPP: - GUJARAT TRACTORS, VADODARA - 390 011 Phone: 0265 - 2356291, Mobile: 9879599402/9925233951 Email: [email protected]TATA POWER COMPANY LTD KALIAN TECHNICAL SESSION – I
POWER CONSULTANTS amp AGENCIES A 198 VISHVAMITRY TOWNSHIP OPP - GUJARAT TRACTORS VADODARA - 390 011
Phone 0265 - 2356291 Mobile 98795994029925233951
Email smtakalkaryahoocom
TATA POWER COMPANY LTD
KALIAN
TECHNICAL SESSION ndash I
Power Consultants amp Agencies Page 2
CONSTRUCTION OF EHV TRANSMISSION LINES
10 Introduction 11 Construction of EHV Transmission line is a very specific and specialized job It involves lot of
precision and accuracy The transmission line is standing for many years in the open terrain and faces vagaries of nature The construction practice should therefore ensure that the parameters on which the design of transmission line is made are not exceeded
12 The construction mainly includes the following activities
bull Survey amp Alignment
bull Foundation Work
bull Erection of Super Structure
bull Stringing of Shield wire amp Conductor
bull Testing amp Commissioning 13 Each of above activity can be further divided into sub‐activities All the erection activities are based on the design inputs as well as site situation For example the type of tower and foundation to be adopted will depend upon the profile amp site situation where as the spandeviation angle limitations will be based on the design factors of the tower This part deals with the general specifications for construction of EHV lines
20 Survey amp Alignment 21 Whenever EHV transmission line is to be constructed between two subs‐stations the ideal route length will be the direct topographical distance between the two stations However this will not be possible as number of obstructions in the form of villages town important civil establishments big ponds rivers etc will prevent the straight run of the line The obstruction will result into line deviations It will therefore be necessary to carry out survey by various means The survey will establish the following
bull The topography of the route of the line bull The important deviation points of the line bull The approximate quantity of Towers and extension bull First hand information regarding the soil strata along the route leading to approximate
estimation of foundation work quantities bull The obstructions which may result into line deviations bull Major River Railway Road and Power line crossings and type of structures for the same bull Information regarding availability of inputs for foundation work (cement aggregates steel and
water) bull Right of way problems which are likely along the route bull Cost of transportation of material to various locations bull Tentative time frame for completing the work
22 It is also usual to make trial pits or carry out soil investigation along the proposed route of the transmission line at certain fixed interval or at the points where abrupt change in soil strata is suspected This exercise results in to the approximate estimation of the foundation types and
Power Consultants amp Agencies Page 3
excavationconcrete volumes and the re‐enforcement for the foundation work The various stages of survey works are described in details as under 23 Reconnaissance and Route Alignment Survey 231 A provisional route of transmission line is initially plotted on survey maps (topo sheets) and a reconnaissance walkover survey is carried out This is essential to fix up angle tower positions tentatively since many of the physical features on the ground may not be clearly available in the survey map due to developments that might have taken place subsequent to the preparation of the maps by department of survey of India The topo sheets are obtained from the office of The Survey of India Deharadoon by indicating the Longitude amp the Lattitude of the proposed route of the transmission line In most of the cases more than one Topo sheets are required to cover the route of the line
SCHEMATIC ROUTE ALIGNMENT SURVEY
ROUTE MAP
22deg1
5
EXISTIN
G 400 KV TO
WER LI
NE
DAM
DAM
198 VISHWAMITRI TOWN SHIP OPP GUJARAT TRACTORS VADODARA-390 011
SURVEYED amp PREPARED BY-
POWER CONSULTANTS amp AGENCIES VADODARA
BY CHKD APPD PROJENGR
DRAWING NO REV
REVISIONS
0E
DATE
PCAACKBPL400kVRECCAYRM-01
RECONNAISSANCE SURVEY OF 400 kV DC
1 50000
SCALE
Project
Title
NO
wwwpowerconsultantinfo
EXISTING 400 KV DC LI
NE
TREE PLANT
Dhadhipara
Batra
Lahrapara
Nagrahi
T-05
T-05
T-05
T-05
T-05
CA
RT
TR
AC
K
Metal Road
Cart
Trac
k
METAL ROAD
CA
RT
TRA
CK
RCC
RCC
CA
RT
TR
AC
K
ROAD
L 05
3
22deg2
022
deg25
22deg2
522
deg20
22deg1
5
82deg3082deg2582deg2082deg1582deg10
82deg3082deg2582deg2082deg1582deg10
Borewells
200
200
PO
PS
RF PF
Tree
Police station
ReservedProtected forest
Post office
Bench-mark
Heights point
Heights triangulated
Hutment
Wells lined unlined
SYMBOLSYMBOLDESCRIPTION DESCRIPTION
Forest
Pond
Temple Mosque
Development
Roads metalledAsphalted road
Roads unmetalled
Railways broad gauge
200Contours with heights
PowerTelephone line
Railways other gauge
Towns or Villages
RiverProposed route with AP
N
Industries
LEGEND -
Cart-track
Canal
Stream
Scrub
Boundary state
Boundary tahsil
Boundary district
400KV DC KASAIPALLI TO BHARARI TRANSMISSION LINE
INDIA(NTS)
BAY OF BENGAL
TAM
ILNA
DU
INDIAN OCEANLANKA
KERALA
SRI
HIMACHAL
CHHATISGARH
MADHYA PRADESH
KARNATAKA
PRADESH
ANDHRA
MAHARASHTRA ORISSA
UTTARANCHAL
NEPALUTTARRAJASTHAN PRADESH
PUNJAB
HARYANA
PRADESH
DELHI
ASSAMPRADESH
BHUTAN
MEGHALAYA
BANGLADESH
JHARKHAND
BENGALWEST
BIHAR
MIZORAM
MANIPUR
NAGALAND
ARUNACHAL
KASHMIRJAMMU amp
N
AR
AB
IAN
SEA
GUJARAT
Coal Bearing Area
Coal Zone Alotment Area
82deg35
82deg35
CHAPI WATER SCHEME
END POINTPROPOSED BHARARI
SUB POOLING STATION
EAST OFKARTALI
AREA BETWEENKARTALI amp DIPKA
NUNBERA
RATIJA
DIPKA
GEVRA
PONRI
NARAIBODH
SITE FOR DIPKA COLONY
KARTALIBLOCK
SARAIPALIBLOCK
DUMARKACHHARBLOCK
BANKI
BAGDEWA DILWADIH
SINGHALIBLOCK
BLOCKBLOCK
BLOCK
PROPOSED COALEXTENSION AREA
COALEXTENSIONAREA
PROPOSED
BHILAI
N O N C O A L Z O N E A R E A
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
CO
AL BEARIN
G AREA
EXISTING POWER PLANTCKBD 2 x 30 MW
START POINTPROPOSED 400 kV
SWITCH YARD
132 kV POWER STATIONPROPOSED 2x50 MW RATIJA
SWITCH YARD
ROUTE OF PROPOSED 400kV
TRANSMISSION LINE
TOTAL LENGTH STATEMENT
DESCRIPTION ROUTE Length(Km)
1
SrNo
54867PROPOSED 400kV DC TRANSMISSION LINE
FROM KASAIPALI TO BHARARI
20
3060
40
7080
90
100
170
180
200210
220
240
250
260
270
300
290
280
310
320
340
350
360
370
380
390400
410
420
430440
450
460
10110
120
150
50
130140
160
190
230
330
GANTRY
181182183184185186221
222
223
224
303 301
302
191192
201
202
203
204
211212213214215
231232
233234
235
241
242
243
251
252
253
271
272
281282
283284
291292293294304
305
306
331
332
333
341
342
343
344
345
346
347
348
351
361
362
371
372
373
381382
383391392393394
401402
403404
405406
407408
4094010
4011
411412413421
422
431432
433441
442
451452
171
161141
111
101102
103
91
92
81827172
6A0
4A0
2122
23
232 The reconnaissance survey helps in collecting the first hand information regarding various important field data required for transmission line works The reconnaissance survey is carried out
COMPAQ
COMPAQ
Route Mapdwg
COMPAQ
SCHEMATIC ROUTE ALIGNMENT SURVEYdwg
Power Consultants amp Agencies Page 4
by using GPS (Geographical Positioning System) The general points to be kept in view while establishing the preliminary route at the time of reconnaissance survey are as under a) The route should be as short and as straight as possible b) Where ever possible attempt should be made to lay the line near to or along roadway Alternatively the line should be approachable to the extent possible c) The number of angle towers should minimum and within these the number of heavier angle towers shall be as less as possible d) Cost of securing and clearing right of way (ROW) making access roads and time required for these works should be minimum e) Corridor through which line is taken should be free from Encumbrances such as non‐Agricultural land notified area Defense establishment oil amp gas establishment acquired mining areas etc f) Care is also required to be taken that the line route avoids any big planned development in the region such as Airport State Industrial Estate Mega Power Projects etc If this is not done shifting of the line may be required later or objection to the construction may occur g) Crossing with permanent objects such as Railway lines and roads should be made preferably at right angles h) In case of hilly terrain it is necessary to conduct detailed survey and locate the tower positions suitable to the topography Detailed survey is recommended for such terrain i) The reconnaissance survey will also establish if we can avoid the following
bull Marshy areas low lying lands river beds earth slip zones etc involving risk to stability of foundation amp the tower
bull Areas subjected to floods gushing ndash culverts during rainy seasons tanks ponds lakes snow blizzards
bull Inaccessible areas where approach roads are not possible bull Areas which will create problems of right of way and way leave bull Route involving abrupt changes in levels too many long spans river or power line crossings or
near parallelism to telecommunication lines bull Thick forest or areas involving heavy compensatory payments for the ROW
j) The reconnaissance survey is useful for collecting the first hand information about various important field data required for transmission line construction which are as under
bull Major power line crossing details (66 KV and above) bull Railway crossing details bull Major river crossing details bull Source of construction materials viz metal sand water etc along the line bull Important rail heads for the purpose of receipt of materials bull Important villages or Railway stations along the route for the purpose of selection of labor
camps bull Nature of soil strata likely to be encountered along the route and the terrain bull Availability of skilled semiskilled and un‐skilled labor their present rate on daily basis or on
contract basis bull Names of the major towns for the purpose of selection of site offices bull Likely local support or hindrance from various section of population along the route of the line
Power Consultants amp Agencies Page 5
For fixing the final alignment and angle points on the ground as per the reconnaissance survey route alignment survey shall be carried out with the help of Theodolite andor Total Station survey chainsmeasuring tapes etc 24 Detailed Survey 241 The main objective of carrying out detailed survey is to prepare longitudinal and cross section profiles on the approved route alignment and to prepare the route plan showing details of deviation angles important objects coming within the right of way and show the landmark pointsobjects along the route with their distance from the alignment of line Work of detailed survey is normally done in two stages
1 By actual field observation taking level readings and calculating distances level differences deflection angles offset distances etc
2 By plotting of profiles on graphed tracing papers of mm x mm size 242 The use of Total Station facilitates quick measurement of distance ground levels and the angles between the two reference points The Total Station is located at fixed point and there after the prism mounted in a stand is moved along the route of the line preferably at an interval of 20 metres Each reading gives the distance and level difference These readings are stored in the memory of Total Station (TS) The data is there after transferred to the computer 243 Field Observation Recording and Calculations 2431 The method of taking level readings for preparation of longitudinal and cross section profile can be one of the following
bull By chain and dumpy level bull By tachometric survey with Theodolite bull By using Total Station and the prism
First method is more useful in plain areas where chaining can be done easily with the help of semiskilled surveyors Tachometric method offers a great advantage in hilly regions and such other inaccessible places where chaining is not possible This method needs skilled surveyors having good understanding of the use of Theodolite and basic knowledge of trigonometry In this method both traversing and leveling is done by means of a tachometric Theodolite The horizontal and vertical distances are computed with the help of readings of the stadia wires taken on the staff held at the reading point The accuracy of the work will depend upon the quality and cost of the equipment The range of operation of Theodolite is much higher than the dumpy level The surveyor and his team will move on an approved route and take ground levels in the field book at an interval of 20 to 30 meters 2432 As stated in 242 above the Total Station is the most modern equipment for surveying It saves lot of time and the observations are highly accurate This equipment is very expensive and needs lot of precautions in handling If the length of line is very short Theodolite can also serve the purpose 25 Plotting of Profiles 251 From the field book entries route plan and longitudinal profile commonly referred to as ldquoroute profilerdquo or ldquosurvey chartrdquo is prepared in the drawing office These charts are prepared and plotted on 1mm5mm1cm square paper of formed drawing sheets of graphed tracing paper The scale normally preferred is 1200mm‐vertical 12000mm‐horizontal 252 The profile shall include the following
Power Consultants amp Agencies Page 6
bull The longitudinal profiles along the centre‐line of the transmission line route including the bottom conductor catenaries
bull The cross‐section profile wherever appreciable difference in level exists with references to centre‐line level In such cases the cross‐section levels shall be taken at each 50100m intervals
bull Route plan giving details of all objects lying within the right of way and just along the boundary of right of way
bull Angle of line deviation duly marked left (L) or right (R) as the case may be bull Objects and their distances along the route within the right of way from centre line nearby
villages important pucca roads amp or riverscanals cart tracks etc should be marked on the route profile
bull Crossing details with any other power or telecommunication lines roads railway lines canals or rivers should be marked as clearly as possible
bull Readings should be taken and charts should show levels of roads canal embankments maximum waterflood levels railway rail top levels heights of supportslines being crossed all trees coming within the clearance zone
bull It is advisable to prepare an independent route profile for Major River crossing section deploying tall special towers or normal towers on piles in the river crossing section as the river crossing is a special task in the construction process which involves special design
26 Tower Spotting 261 The work of tower spotting is a very precise job as it has an implication on overall cost After the tower designs are finalized the tower spotting chart or structure limitation charts are prepared Similarly the drawing of the sag template and its replica is prepared on Acrylic sheet Application of Sag Template helps to decide optimum tower position on Survey Chart which ultimately helps in finalizing the quantity of each type of tower and their extensions (3 meter amp 6 meter etc) 27 Preparation of Sag Template 271 Sag template is a very important tool for the surveyor by the help of which Tower spotting can be done Depending upon the maximum specified permissible temperature of the conductor and zero wind condition the ground clearance is to be maintained by the line Similarly under the specified minimum temperature of the conductor surface with zero wind condition the tower tensions should be within the specified limits The sag template curves are first prepared on tracing paper and the blue print is taken out from the tracing Their replicas on Acrylic sheets are prepared with the itching process The Acrylic sheets are normally 25 to 3 mm thick 272 The sag templates have the following curves itched on them
bull lsquoCold or Uplift Curversquo‐Showing sag of conductor at specified minimum temperature and zero wind
bull lsquoHotrsquo or lsquoMaximum Sag Curversquo showing maximum sag of conductor under zero wind and maximum temperature and sag tolerances are also allowed to take care of stringing error conductor creep or snow incidences
bull Ground clearance Curve‐Drawn parallel to hot curve and at a distance equal to specified minimum ground clearance
Power Consultants amp Agencies Page 7
bull Tower footing Curve‐For normal tower drawn parallel to hot curve under ground clearance curve and separated by a distance equal to maximum sag at design span
273 In erecting an overhead line all the spans cannot be kept equal to normal design span because of the profile of the ground and proper ground and object clearance considerations A constant tension is calculated which will be uniform throughout the Section (from one tension tower to other tension tower) however the sags in individual spans will vary according to their respective spans The lsquoCold and Hotrsquo Template Curves are plotted as parabola to the same scale as the survey chart for the minimum and maximum sags for the normal span (specified in the tender specifications)
28 Application of Sag Template for Tower Spotting 281 The Sag Template is an important tool for correct spotting of the towers after the detailed survey work is completed The following are the steps to be followed for correct application of sag template
bull The acrylic sag template is applied to the ground profile by moving the same horizontally while always ensuring that the vertical axis is held vertical with reference to graphed lines of the tracing paper below
bull The structure positions are marked where the tower footing curve just touches the profile while the ground clearance curve is just clear and above the profile to the left or right of the centre line up to a distance equal to maximum cross area spread on either side
bull Besides normal ground clearance the clearances between power conductor and objects like other power or telecommunication lines houses trolley wires roads railway tracks canal embankments etc shall be checked
bull Extra clearance can be obtained either by reducing the span or providing extension to tower body depending on which alternative is most economical
bull The weight span on either side of a tower can be easily obtained by marking the low points of sags (Null Point) in two adjacent spans and then reading the distance between the two
bull On inclined spans null point may be outside the span
Power Consultants amp Agencies Page 8
bull This indicates that the total weight of conductor is taken up by the higher tower and the lower tower is being pulled up by a force equal to the weight of conductor between lower support and the null point
bull Should the upward pull of the uphill span becomes greater than downward load of the next adjacent span actual uplift will be caused and the conductor would tend to wing clear of the tower upwards
bull For any easy check of whether a tower is under uplift or not the following method may be adopted
bull The Template is applied horizontally until the tops of alternate supports coincide with the Cold Curve
bull If the support is under uplift and has to be extended so as to be above it and in case requisite standard body extension do not suffice for doing this tower which is designed to take uplift will have to be used
bull However for the stability of the line it is not desirable to place a tower in such a position where it is always under permanent uplift condition
bull In case it becomes mandatory due to route compulsion the cross‐arms of the tower subjected to up lift shall be designed to take the extra upward pull
bull The intermediate spans shall be as near as possible to the normal design span bull In case an individual span becomes too short on account of undulations in ground
profiles one or more line supports of the Section may be extended by inserting standard body extensions
bull Even if the line does not deviate for a long run sections have to be provided after every 12 to 15 tangent towers (ie 3 to 4 km length)
bull For this purpose a small angle tension tower designed for 15deg should only be used bull This is mandatory to afford better stability of the line against Transverse wind forces
and to facilitate easy stringing bull Besides 15deg angle tension tower is most economical amongst the standard angle tension
towers 29 Use of computer for preparing sag template and the tower spotting 291 Before taking up the tower design on hand Sag and Tension charts are required to be prepared These charts indicate the values of sag and tension of conductor and the earth wire at Maximum temperature minimum temperature and every‐day temperature under 10036(66) and 0 wind pressure Normally in plain terrain in India the maximum minimum and every‐day temperatures are considered as 0 DegC 75 Deg C and 32Deg C These values may change in the region experiencing snow or Sub‐Zero temperatures If the conductor is required to carry large block of power the maximum surface temperature of conductor can be taken up to 95Deg C For Earth wires the maximum temperature is taken as 53Deg C 292 Based on the sag tension charts the sag template curves can be plotted on the computer through a specific programme The full scale print out of the curves is then used to prepare the Acrylic Sag Template by itching process 210 Towers Spotting Data 2101 Since each tower is designed to withstand a definite load only in each of transverse vertical and longitudinal directions the surveyor must know these limitations for the various types of towers
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 2
CONSTRUCTION OF EHV TRANSMISSION LINES
10 Introduction 11 Construction of EHV Transmission line is a very specific and specialized job It involves lot of
precision and accuracy The transmission line is standing for many years in the open terrain and faces vagaries of nature The construction practice should therefore ensure that the parameters on which the design of transmission line is made are not exceeded
12 The construction mainly includes the following activities
bull Survey amp Alignment
bull Foundation Work
bull Erection of Super Structure
bull Stringing of Shield wire amp Conductor
bull Testing amp Commissioning 13 Each of above activity can be further divided into sub‐activities All the erection activities are based on the design inputs as well as site situation For example the type of tower and foundation to be adopted will depend upon the profile amp site situation where as the spandeviation angle limitations will be based on the design factors of the tower This part deals with the general specifications for construction of EHV lines
20 Survey amp Alignment 21 Whenever EHV transmission line is to be constructed between two subs‐stations the ideal route length will be the direct topographical distance between the two stations However this will not be possible as number of obstructions in the form of villages town important civil establishments big ponds rivers etc will prevent the straight run of the line The obstruction will result into line deviations It will therefore be necessary to carry out survey by various means The survey will establish the following
bull The topography of the route of the line bull The important deviation points of the line bull The approximate quantity of Towers and extension bull First hand information regarding the soil strata along the route leading to approximate
estimation of foundation work quantities bull The obstructions which may result into line deviations bull Major River Railway Road and Power line crossings and type of structures for the same bull Information regarding availability of inputs for foundation work (cement aggregates steel and
water) bull Right of way problems which are likely along the route bull Cost of transportation of material to various locations bull Tentative time frame for completing the work
22 It is also usual to make trial pits or carry out soil investigation along the proposed route of the transmission line at certain fixed interval or at the points where abrupt change in soil strata is suspected This exercise results in to the approximate estimation of the foundation types and
Power Consultants amp Agencies Page 3
excavationconcrete volumes and the re‐enforcement for the foundation work The various stages of survey works are described in details as under 23 Reconnaissance and Route Alignment Survey 231 A provisional route of transmission line is initially plotted on survey maps (topo sheets) and a reconnaissance walkover survey is carried out This is essential to fix up angle tower positions tentatively since many of the physical features on the ground may not be clearly available in the survey map due to developments that might have taken place subsequent to the preparation of the maps by department of survey of India The topo sheets are obtained from the office of The Survey of India Deharadoon by indicating the Longitude amp the Lattitude of the proposed route of the transmission line In most of the cases more than one Topo sheets are required to cover the route of the line
SCHEMATIC ROUTE ALIGNMENT SURVEY
ROUTE MAP
22deg1
5
EXISTIN
G 400 KV TO
WER LI
NE
DAM
DAM
198 VISHWAMITRI TOWN SHIP OPP GUJARAT TRACTORS VADODARA-390 011
SURVEYED amp PREPARED BY-
POWER CONSULTANTS amp AGENCIES VADODARA
BY CHKD APPD PROJENGR
DRAWING NO REV
REVISIONS
0E
DATE
PCAACKBPL400kVRECCAYRM-01
RECONNAISSANCE SURVEY OF 400 kV DC
1 50000
SCALE
Project
Title
NO
wwwpowerconsultantinfo
EXISTING 400 KV DC LI
NE
TREE PLANT
Dhadhipara
Batra
Lahrapara
Nagrahi
T-05
T-05
T-05
T-05
T-05
CA
RT
TR
AC
K
Metal Road
Cart
Trac
k
METAL ROAD
CA
RT
TRA
CK
RCC
RCC
CA
RT
TR
AC
K
ROAD
L 05
3
22deg2
022
deg25
22deg2
522
deg20
22deg1
5
82deg3082deg2582deg2082deg1582deg10
82deg3082deg2582deg2082deg1582deg10
Borewells
200
200
PO
PS
RF PF
Tree
Police station
ReservedProtected forest
Post office
Bench-mark
Heights point
Heights triangulated
Hutment
Wells lined unlined
SYMBOLSYMBOLDESCRIPTION DESCRIPTION
Forest
Pond
Temple Mosque
Development
Roads metalledAsphalted road
Roads unmetalled
Railways broad gauge
200Contours with heights
PowerTelephone line
Railways other gauge
Towns or Villages
RiverProposed route with AP
N
Industries
LEGEND -
Cart-track
Canal
Stream
Scrub
Boundary state
Boundary tahsil
Boundary district
400KV DC KASAIPALLI TO BHARARI TRANSMISSION LINE
INDIA(NTS)
BAY OF BENGAL
TAM
ILNA
DU
INDIAN OCEANLANKA
KERALA
SRI
HIMACHAL
CHHATISGARH
MADHYA PRADESH
KARNATAKA
PRADESH
ANDHRA
MAHARASHTRA ORISSA
UTTARANCHAL
NEPALUTTARRAJASTHAN PRADESH
PUNJAB
HARYANA
PRADESH
DELHI
ASSAMPRADESH
BHUTAN
MEGHALAYA
BANGLADESH
JHARKHAND
BENGALWEST
BIHAR
MIZORAM
MANIPUR
NAGALAND
ARUNACHAL
KASHMIRJAMMU amp
N
AR
AB
IAN
SEA
GUJARAT
Coal Bearing Area
Coal Zone Alotment Area
82deg35
82deg35
CHAPI WATER SCHEME
END POINTPROPOSED BHARARI
SUB POOLING STATION
EAST OFKARTALI
AREA BETWEENKARTALI amp DIPKA
NUNBERA
RATIJA
DIPKA
GEVRA
PONRI
NARAIBODH
SITE FOR DIPKA COLONY
KARTALIBLOCK
SARAIPALIBLOCK
DUMARKACHHARBLOCK
BANKI
BAGDEWA DILWADIH
SINGHALIBLOCK
BLOCKBLOCK
BLOCK
PROPOSED COALEXTENSION AREA
COALEXTENSIONAREA
PROPOSED
BHILAI
N O N C O A L Z O N E A R E A
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
CO
AL BEARIN
G AREA
EXISTING POWER PLANTCKBD 2 x 30 MW
START POINTPROPOSED 400 kV
SWITCH YARD
132 kV POWER STATIONPROPOSED 2x50 MW RATIJA
SWITCH YARD
ROUTE OF PROPOSED 400kV
TRANSMISSION LINE
TOTAL LENGTH STATEMENT
DESCRIPTION ROUTE Length(Km)
1
SrNo
54867PROPOSED 400kV DC TRANSMISSION LINE
FROM KASAIPALI TO BHARARI
20
3060
40
7080
90
100
170
180
200210
220
240
250
260
270
300
290
280
310
320
340
350
360
370
380
390400
410
420
430440
450
460
10110
120
150
50
130140
160
190
230
330
GANTRY
181182183184185186221
222
223
224
303 301
302
191192
201
202
203
204
211212213214215
231232
233234
235
241
242
243
251
252
253
271
272
281282
283284
291292293294304
305
306
331
332
333
341
342
343
344
345
346
347
348
351
361
362
371
372
373
381382
383391392393394
401402
403404
405406
407408
4094010
4011
411412413421
422
431432
433441
442
451452
171
161141
111
101102
103
91
92
81827172
6A0
4A0
2122
23
232 The reconnaissance survey helps in collecting the first hand information regarding various important field data required for transmission line works The reconnaissance survey is carried out
COMPAQ
COMPAQ
Route Mapdwg
COMPAQ
SCHEMATIC ROUTE ALIGNMENT SURVEYdwg
Power Consultants amp Agencies Page 4
by using GPS (Geographical Positioning System) The general points to be kept in view while establishing the preliminary route at the time of reconnaissance survey are as under a) The route should be as short and as straight as possible b) Where ever possible attempt should be made to lay the line near to or along roadway Alternatively the line should be approachable to the extent possible c) The number of angle towers should minimum and within these the number of heavier angle towers shall be as less as possible d) Cost of securing and clearing right of way (ROW) making access roads and time required for these works should be minimum e) Corridor through which line is taken should be free from Encumbrances such as non‐Agricultural land notified area Defense establishment oil amp gas establishment acquired mining areas etc f) Care is also required to be taken that the line route avoids any big planned development in the region such as Airport State Industrial Estate Mega Power Projects etc If this is not done shifting of the line may be required later or objection to the construction may occur g) Crossing with permanent objects such as Railway lines and roads should be made preferably at right angles h) In case of hilly terrain it is necessary to conduct detailed survey and locate the tower positions suitable to the topography Detailed survey is recommended for such terrain i) The reconnaissance survey will also establish if we can avoid the following
bull Marshy areas low lying lands river beds earth slip zones etc involving risk to stability of foundation amp the tower
bull Areas subjected to floods gushing ndash culverts during rainy seasons tanks ponds lakes snow blizzards
bull Inaccessible areas where approach roads are not possible bull Areas which will create problems of right of way and way leave bull Route involving abrupt changes in levels too many long spans river or power line crossings or
near parallelism to telecommunication lines bull Thick forest or areas involving heavy compensatory payments for the ROW
j) The reconnaissance survey is useful for collecting the first hand information about various important field data required for transmission line construction which are as under
bull Major power line crossing details (66 KV and above) bull Railway crossing details bull Major river crossing details bull Source of construction materials viz metal sand water etc along the line bull Important rail heads for the purpose of receipt of materials bull Important villages or Railway stations along the route for the purpose of selection of labor
camps bull Nature of soil strata likely to be encountered along the route and the terrain bull Availability of skilled semiskilled and un‐skilled labor their present rate on daily basis or on
contract basis bull Names of the major towns for the purpose of selection of site offices bull Likely local support or hindrance from various section of population along the route of the line
Power Consultants amp Agencies Page 5
For fixing the final alignment and angle points on the ground as per the reconnaissance survey route alignment survey shall be carried out with the help of Theodolite andor Total Station survey chainsmeasuring tapes etc 24 Detailed Survey 241 The main objective of carrying out detailed survey is to prepare longitudinal and cross section profiles on the approved route alignment and to prepare the route plan showing details of deviation angles important objects coming within the right of way and show the landmark pointsobjects along the route with their distance from the alignment of line Work of detailed survey is normally done in two stages
1 By actual field observation taking level readings and calculating distances level differences deflection angles offset distances etc
2 By plotting of profiles on graphed tracing papers of mm x mm size 242 The use of Total Station facilitates quick measurement of distance ground levels and the angles between the two reference points The Total Station is located at fixed point and there after the prism mounted in a stand is moved along the route of the line preferably at an interval of 20 metres Each reading gives the distance and level difference These readings are stored in the memory of Total Station (TS) The data is there after transferred to the computer 243 Field Observation Recording and Calculations 2431 The method of taking level readings for preparation of longitudinal and cross section profile can be one of the following
bull By chain and dumpy level bull By tachometric survey with Theodolite bull By using Total Station and the prism
First method is more useful in plain areas where chaining can be done easily with the help of semiskilled surveyors Tachometric method offers a great advantage in hilly regions and such other inaccessible places where chaining is not possible This method needs skilled surveyors having good understanding of the use of Theodolite and basic knowledge of trigonometry In this method both traversing and leveling is done by means of a tachometric Theodolite The horizontal and vertical distances are computed with the help of readings of the stadia wires taken on the staff held at the reading point The accuracy of the work will depend upon the quality and cost of the equipment The range of operation of Theodolite is much higher than the dumpy level The surveyor and his team will move on an approved route and take ground levels in the field book at an interval of 20 to 30 meters 2432 As stated in 242 above the Total Station is the most modern equipment for surveying It saves lot of time and the observations are highly accurate This equipment is very expensive and needs lot of precautions in handling If the length of line is very short Theodolite can also serve the purpose 25 Plotting of Profiles 251 From the field book entries route plan and longitudinal profile commonly referred to as ldquoroute profilerdquo or ldquosurvey chartrdquo is prepared in the drawing office These charts are prepared and plotted on 1mm5mm1cm square paper of formed drawing sheets of graphed tracing paper The scale normally preferred is 1200mm‐vertical 12000mm‐horizontal 252 The profile shall include the following
Power Consultants amp Agencies Page 6
bull The longitudinal profiles along the centre‐line of the transmission line route including the bottom conductor catenaries
bull The cross‐section profile wherever appreciable difference in level exists with references to centre‐line level In such cases the cross‐section levels shall be taken at each 50100m intervals
bull Route plan giving details of all objects lying within the right of way and just along the boundary of right of way
bull Angle of line deviation duly marked left (L) or right (R) as the case may be bull Objects and their distances along the route within the right of way from centre line nearby
villages important pucca roads amp or riverscanals cart tracks etc should be marked on the route profile
bull Crossing details with any other power or telecommunication lines roads railway lines canals or rivers should be marked as clearly as possible
bull Readings should be taken and charts should show levels of roads canal embankments maximum waterflood levels railway rail top levels heights of supportslines being crossed all trees coming within the clearance zone
bull It is advisable to prepare an independent route profile for Major River crossing section deploying tall special towers or normal towers on piles in the river crossing section as the river crossing is a special task in the construction process which involves special design
26 Tower Spotting 261 The work of tower spotting is a very precise job as it has an implication on overall cost After the tower designs are finalized the tower spotting chart or structure limitation charts are prepared Similarly the drawing of the sag template and its replica is prepared on Acrylic sheet Application of Sag Template helps to decide optimum tower position on Survey Chart which ultimately helps in finalizing the quantity of each type of tower and their extensions (3 meter amp 6 meter etc) 27 Preparation of Sag Template 271 Sag template is a very important tool for the surveyor by the help of which Tower spotting can be done Depending upon the maximum specified permissible temperature of the conductor and zero wind condition the ground clearance is to be maintained by the line Similarly under the specified minimum temperature of the conductor surface with zero wind condition the tower tensions should be within the specified limits The sag template curves are first prepared on tracing paper and the blue print is taken out from the tracing Their replicas on Acrylic sheets are prepared with the itching process The Acrylic sheets are normally 25 to 3 mm thick 272 The sag templates have the following curves itched on them
bull lsquoCold or Uplift Curversquo‐Showing sag of conductor at specified minimum temperature and zero wind
bull lsquoHotrsquo or lsquoMaximum Sag Curversquo showing maximum sag of conductor under zero wind and maximum temperature and sag tolerances are also allowed to take care of stringing error conductor creep or snow incidences
bull Ground clearance Curve‐Drawn parallel to hot curve and at a distance equal to specified minimum ground clearance
Power Consultants amp Agencies Page 7
bull Tower footing Curve‐For normal tower drawn parallel to hot curve under ground clearance curve and separated by a distance equal to maximum sag at design span
273 In erecting an overhead line all the spans cannot be kept equal to normal design span because of the profile of the ground and proper ground and object clearance considerations A constant tension is calculated which will be uniform throughout the Section (from one tension tower to other tension tower) however the sags in individual spans will vary according to their respective spans The lsquoCold and Hotrsquo Template Curves are plotted as parabola to the same scale as the survey chart for the minimum and maximum sags for the normal span (specified in the tender specifications)
28 Application of Sag Template for Tower Spotting 281 The Sag Template is an important tool for correct spotting of the towers after the detailed survey work is completed The following are the steps to be followed for correct application of sag template
bull The acrylic sag template is applied to the ground profile by moving the same horizontally while always ensuring that the vertical axis is held vertical with reference to graphed lines of the tracing paper below
bull The structure positions are marked where the tower footing curve just touches the profile while the ground clearance curve is just clear and above the profile to the left or right of the centre line up to a distance equal to maximum cross area spread on either side
bull Besides normal ground clearance the clearances between power conductor and objects like other power or telecommunication lines houses trolley wires roads railway tracks canal embankments etc shall be checked
bull Extra clearance can be obtained either by reducing the span or providing extension to tower body depending on which alternative is most economical
bull The weight span on either side of a tower can be easily obtained by marking the low points of sags (Null Point) in two adjacent spans and then reading the distance between the two
bull On inclined spans null point may be outside the span
Power Consultants amp Agencies Page 8
bull This indicates that the total weight of conductor is taken up by the higher tower and the lower tower is being pulled up by a force equal to the weight of conductor between lower support and the null point
bull Should the upward pull of the uphill span becomes greater than downward load of the next adjacent span actual uplift will be caused and the conductor would tend to wing clear of the tower upwards
bull For any easy check of whether a tower is under uplift or not the following method may be adopted
bull The Template is applied horizontally until the tops of alternate supports coincide with the Cold Curve
bull If the support is under uplift and has to be extended so as to be above it and in case requisite standard body extension do not suffice for doing this tower which is designed to take uplift will have to be used
bull However for the stability of the line it is not desirable to place a tower in such a position where it is always under permanent uplift condition
bull In case it becomes mandatory due to route compulsion the cross‐arms of the tower subjected to up lift shall be designed to take the extra upward pull
bull The intermediate spans shall be as near as possible to the normal design span bull In case an individual span becomes too short on account of undulations in ground
profiles one or more line supports of the Section may be extended by inserting standard body extensions
bull Even if the line does not deviate for a long run sections have to be provided after every 12 to 15 tangent towers (ie 3 to 4 km length)
bull For this purpose a small angle tension tower designed for 15deg should only be used bull This is mandatory to afford better stability of the line against Transverse wind forces
and to facilitate easy stringing bull Besides 15deg angle tension tower is most economical amongst the standard angle tension
towers 29 Use of computer for preparing sag template and the tower spotting 291 Before taking up the tower design on hand Sag and Tension charts are required to be prepared These charts indicate the values of sag and tension of conductor and the earth wire at Maximum temperature minimum temperature and every‐day temperature under 10036(66) and 0 wind pressure Normally in plain terrain in India the maximum minimum and every‐day temperatures are considered as 0 DegC 75 Deg C and 32Deg C These values may change in the region experiencing snow or Sub‐Zero temperatures If the conductor is required to carry large block of power the maximum surface temperature of conductor can be taken up to 95Deg C For Earth wires the maximum temperature is taken as 53Deg C 292 Based on the sag tension charts the sag template curves can be plotted on the computer through a specific programme The full scale print out of the curves is then used to prepare the Acrylic Sag Template by itching process 210 Towers Spotting Data 2101 Since each tower is designed to withstand a definite load only in each of transverse vertical and longitudinal directions the surveyor must know these limitations for the various types of towers
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 3
excavationconcrete volumes and the re‐enforcement for the foundation work The various stages of survey works are described in details as under 23 Reconnaissance and Route Alignment Survey 231 A provisional route of transmission line is initially plotted on survey maps (topo sheets) and a reconnaissance walkover survey is carried out This is essential to fix up angle tower positions tentatively since many of the physical features on the ground may not be clearly available in the survey map due to developments that might have taken place subsequent to the preparation of the maps by department of survey of India The topo sheets are obtained from the office of The Survey of India Deharadoon by indicating the Longitude amp the Lattitude of the proposed route of the transmission line In most of the cases more than one Topo sheets are required to cover the route of the line
SCHEMATIC ROUTE ALIGNMENT SURVEY
ROUTE MAP
22deg1
5
EXISTIN
G 400 KV TO
WER LI
NE
DAM
DAM
198 VISHWAMITRI TOWN SHIP OPP GUJARAT TRACTORS VADODARA-390 011
SURVEYED amp PREPARED BY-
POWER CONSULTANTS amp AGENCIES VADODARA
BY CHKD APPD PROJENGR
DRAWING NO REV
REVISIONS
0E
DATE
PCAACKBPL400kVRECCAYRM-01
RECONNAISSANCE SURVEY OF 400 kV DC
1 50000
SCALE
Project
Title
NO
wwwpowerconsultantinfo
EXISTING 400 KV DC LI
NE
TREE PLANT
Dhadhipara
Batra
Lahrapara
Nagrahi
T-05
T-05
T-05
T-05
T-05
CA
RT
TR
AC
K
Metal Road
Cart
Trac
k
METAL ROAD
CA
RT
TRA
CK
RCC
RCC
CA
RT
TR
AC
K
ROAD
L 05
3
22deg2
022
deg25
22deg2
522
deg20
22deg1
5
82deg3082deg2582deg2082deg1582deg10
82deg3082deg2582deg2082deg1582deg10
Borewells
200
200
PO
PS
RF PF
Tree
Police station
ReservedProtected forest
Post office
Bench-mark
Heights point
Heights triangulated
Hutment
Wells lined unlined
SYMBOLSYMBOLDESCRIPTION DESCRIPTION
Forest
Pond
Temple Mosque
Development
Roads metalledAsphalted road
Roads unmetalled
Railways broad gauge
200Contours with heights
PowerTelephone line
Railways other gauge
Towns or Villages
RiverProposed route with AP
N
Industries
LEGEND -
Cart-track
Canal
Stream
Scrub
Boundary state
Boundary tahsil
Boundary district
400KV DC KASAIPALLI TO BHARARI TRANSMISSION LINE
INDIA(NTS)
BAY OF BENGAL
TAM
ILNA
DU
INDIAN OCEANLANKA
KERALA
SRI
HIMACHAL
CHHATISGARH
MADHYA PRADESH
KARNATAKA
PRADESH
ANDHRA
MAHARASHTRA ORISSA
UTTARANCHAL
NEPALUTTARRAJASTHAN PRADESH
PUNJAB
HARYANA
PRADESH
DELHI
ASSAMPRADESH
BHUTAN
MEGHALAYA
BANGLADESH
JHARKHAND
BENGALWEST
BIHAR
MIZORAM
MANIPUR
NAGALAND
ARUNACHAL
KASHMIRJAMMU amp
N
AR
AB
IAN
SEA
GUJARAT
Coal Bearing Area
Coal Zone Alotment Area
82deg35
82deg35
CHAPI WATER SCHEME
END POINTPROPOSED BHARARI
SUB POOLING STATION
EAST OFKARTALI
AREA BETWEENKARTALI amp DIPKA
NUNBERA
RATIJA
DIPKA
GEVRA
PONRI
NARAIBODH
SITE FOR DIPKA COLONY
KARTALIBLOCK
SARAIPALIBLOCK
DUMARKACHHARBLOCK
BANKI
BAGDEWA DILWADIH
SINGHALIBLOCK
BLOCKBLOCK
BLOCK
PROPOSED COALEXTENSION AREA
COALEXTENSIONAREA
PROPOSED
BHILAI
N O N C O A L Z O N E A R E A
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
COAL BEARING AREA
CO
AL BEARIN
G AREA
EXISTING POWER PLANTCKBD 2 x 30 MW
START POINTPROPOSED 400 kV
SWITCH YARD
132 kV POWER STATIONPROPOSED 2x50 MW RATIJA
SWITCH YARD
ROUTE OF PROPOSED 400kV
TRANSMISSION LINE
TOTAL LENGTH STATEMENT
DESCRIPTION ROUTE Length(Km)
1
SrNo
54867PROPOSED 400kV DC TRANSMISSION LINE
FROM KASAIPALI TO BHARARI
20
3060
40
7080
90
100
170
180
200210
220
240
250
260
270
300
290
280
310
320
340
350
360
370
380
390400
410
420
430440
450
460
10110
120
150
50
130140
160
190
230
330
GANTRY
181182183184185186221
222
223
224
303 301
302
191192
201
202
203
204
211212213214215
231232
233234
235
241
242
243
251
252
253
271
272
281282
283284
291292293294304
305
306
331
332
333
341
342
343
344
345
346
347
348
351
361
362
371
372
373
381382
383391392393394
401402
403404
405406
407408
4094010
4011
411412413421
422
431432
433441
442
451452
171
161141
111
101102
103
91
92
81827172
6A0
4A0
2122
23
232 The reconnaissance survey helps in collecting the first hand information regarding various important field data required for transmission line works The reconnaissance survey is carried out
COMPAQ
COMPAQ
Route Mapdwg
COMPAQ
SCHEMATIC ROUTE ALIGNMENT SURVEYdwg
Power Consultants amp Agencies Page 4
by using GPS (Geographical Positioning System) The general points to be kept in view while establishing the preliminary route at the time of reconnaissance survey are as under a) The route should be as short and as straight as possible b) Where ever possible attempt should be made to lay the line near to or along roadway Alternatively the line should be approachable to the extent possible c) The number of angle towers should minimum and within these the number of heavier angle towers shall be as less as possible d) Cost of securing and clearing right of way (ROW) making access roads and time required for these works should be minimum e) Corridor through which line is taken should be free from Encumbrances such as non‐Agricultural land notified area Defense establishment oil amp gas establishment acquired mining areas etc f) Care is also required to be taken that the line route avoids any big planned development in the region such as Airport State Industrial Estate Mega Power Projects etc If this is not done shifting of the line may be required later or objection to the construction may occur g) Crossing with permanent objects such as Railway lines and roads should be made preferably at right angles h) In case of hilly terrain it is necessary to conduct detailed survey and locate the tower positions suitable to the topography Detailed survey is recommended for such terrain i) The reconnaissance survey will also establish if we can avoid the following
bull Marshy areas low lying lands river beds earth slip zones etc involving risk to stability of foundation amp the tower
bull Areas subjected to floods gushing ndash culverts during rainy seasons tanks ponds lakes snow blizzards
bull Inaccessible areas where approach roads are not possible bull Areas which will create problems of right of way and way leave bull Route involving abrupt changes in levels too many long spans river or power line crossings or
near parallelism to telecommunication lines bull Thick forest or areas involving heavy compensatory payments for the ROW
j) The reconnaissance survey is useful for collecting the first hand information about various important field data required for transmission line construction which are as under
bull Major power line crossing details (66 KV and above) bull Railway crossing details bull Major river crossing details bull Source of construction materials viz metal sand water etc along the line bull Important rail heads for the purpose of receipt of materials bull Important villages or Railway stations along the route for the purpose of selection of labor
camps bull Nature of soil strata likely to be encountered along the route and the terrain bull Availability of skilled semiskilled and un‐skilled labor their present rate on daily basis or on
contract basis bull Names of the major towns for the purpose of selection of site offices bull Likely local support or hindrance from various section of population along the route of the line
Power Consultants amp Agencies Page 5
For fixing the final alignment and angle points on the ground as per the reconnaissance survey route alignment survey shall be carried out with the help of Theodolite andor Total Station survey chainsmeasuring tapes etc 24 Detailed Survey 241 The main objective of carrying out detailed survey is to prepare longitudinal and cross section profiles on the approved route alignment and to prepare the route plan showing details of deviation angles important objects coming within the right of way and show the landmark pointsobjects along the route with their distance from the alignment of line Work of detailed survey is normally done in two stages
1 By actual field observation taking level readings and calculating distances level differences deflection angles offset distances etc
2 By plotting of profiles on graphed tracing papers of mm x mm size 242 The use of Total Station facilitates quick measurement of distance ground levels and the angles between the two reference points The Total Station is located at fixed point and there after the prism mounted in a stand is moved along the route of the line preferably at an interval of 20 metres Each reading gives the distance and level difference These readings are stored in the memory of Total Station (TS) The data is there after transferred to the computer 243 Field Observation Recording and Calculations 2431 The method of taking level readings for preparation of longitudinal and cross section profile can be one of the following
bull By chain and dumpy level bull By tachometric survey with Theodolite bull By using Total Station and the prism
First method is more useful in plain areas where chaining can be done easily with the help of semiskilled surveyors Tachometric method offers a great advantage in hilly regions and such other inaccessible places where chaining is not possible This method needs skilled surveyors having good understanding of the use of Theodolite and basic knowledge of trigonometry In this method both traversing and leveling is done by means of a tachometric Theodolite The horizontal and vertical distances are computed with the help of readings of the stadia wires taken on the staff held at the reading point The accuracy of the work will depend upon the quality and cost of the equipment The range of operation of Theodolite is much higher than the dumpy level The surveyor and his team will move on an approved route and take ground levels in the field book at an interval of 20 to 30 meters 2432 As stated in 242 above the Total Station is the most modern equipment for surveying It saves lot of time and the observations are highly accurate This equipment is very expensive and needs lot of precautions in handling If the length of line is very short Theodolite can also serve the purpose 25 Plotting of Profiles 251 From the field book entries route plan and longitudinal profile commonly referred to as ldquoroute profilerdquo or ldquosurvey chartrdquo is prepared in the drawing office These charts are prepared and plotted on 1mm5mm1cm square paper of formed drawing sheets of graphed tracing paper The scale normally preferred is 1200mm‐vertical 12000mm‐horizontal 252 The profile shall include the following
Power Consultants amp Agencies Page 6
bull The longitudinal profiles along the centre‐line of the transmission line route including the bottom conductor catenaries
bull The cross‐section profile wherever appreciable difference in level exists with references to centre‐line level In such cases the cross‐section levels shall be taken at each 50100m intervals
bull Route plan giving details of all objects lying within the right of way and just along the boundary of right of way
bull Angle of line deviation duly marked left (L) or right (R) as the case may be bull Objects and their distances along the route within the right of way from centre line nearby
villages important pucca roads amp or riverscanals cart tracks etc should be marked on the route profile
bull Crossing details with any other power or telecommunication lines roads railway lines canals or rivers should be marked as clearly as possible
bull Readings should be taken and charts should show levels of roads canal embankments maximum waterflood levels railway rail top levels heights of supportslines being crossed all trees coming within the clearance zone
bull It is advisable to prepare an independent route profile for Major River crossing section deploying tall special towers or normal towers on piles in the river crossing section as the river crossing is a special task in the construction process which involves special design
26 Tower Spotting 261 The work of tower spotting is a very precise job as it has an implication on overall cost After the tower designs are finalized the tower spotting chart or structure limitation charts are prepared Similarly the drawing of the sag template and its replica is prepared on Acrylic sheet Application of Sag Template helps to decide optimum tower position on Survey Chart which ultimately helps in finalizing the quantity of each type of tower and their extensions (3 meter amp 6 meter etc) 27 Preparation of Sag Template 271 Sag template is a very important tool for the surveyor by the help of which Tower spotting can be done Depending upon the maximum specified permissible temperature of the conductor and zero wind condition the ground clearance is to be maintained by the line Similarly under the specified minimum temperature of the conductor surface with zero wind condition the tower tensions should be within the specified limits The sag template curves are first prepared on tracing paper and the blue print is taken out from the tracing Their replicas on Acrylic sheets are prepared with the itching process The Acrylic sheets are normally 25 to 3 mm thick 272 The sag templates have the following curves itched on them
bull lsquoCold or Uplift Curversquo‐Showing sag of conductor at specified minimum temperature and zero wind
bull lsquoHotrsquo or lsquoMaximum Sag Curversquo showing maximum sag of conductor under zero wind and maximum temperature and sag tolerances are also allowed to take care of stringing error conductor creep or snow incidences
bull Ground clearance Curve‐Drawn parallel to hot curve and at a distance equal to specified minimum ground clearance
Power Consultants amp Agencies Page 7
bull Tower footing Curve‐For normal tower drawn parallel to hot curve under ground clearance curve and separated by a distance equal to maximum sag at design span
273 In erecting an overhead line all the spans cannot be kept equal to normal design span because of the profile of the ground and proper ground and object clearance considerations A constant tension is calculated which will be uniform throughout the Section (from one tension tower to other tension tower) however the sags in individual spans will vary according to their respective spans The lsquoCold and Hotrsquo Template Curves are plotted as parabola to the same scale as the survey chart for the minimum and maximum sags for the normal span (specified in the tender specifications)
28 Application of Sag Template for Tower Spotting 281 The Sag Template is an important tool for correct spotting of the towers after the detailed survey work is completed The following are the steps to be followed for correct application of sag template
bull The acrylic sag template is applied to the ground profile by moving the same horizontally while always ensuring that the vertical axis is held vertical with reference to graphed lines of the tracing paper below
bull The structure positions are marked where the tower footing curve just touches the profile while the ground clearance curve is just clear and above the profile to the left or right of the centre line up to a distance equal to maximum cross area spread on either side
bull Besides normal ground clearance the clearances between power conductor and objects like other power or telecommunication lines houses trolley wires roads railway tracks canal embankments etc shall be checked
bull Extra clearance can be obtained either by reducing the span or providing extension to tower body depending on which alternative is most economical
bull The weight span on either side of a tower can be easily obtained by marking the low points of sags (Null Point) in two adjacent spans and then reading the distance between the two
bull On inclined spans null point may be outside the span
Power Consultants amp Agencies Page 8
bull This indicates that the total weight of conductor is taken up by the higher tower and the lower tower is being pulled up by a force equal to the weight of conductor between lower support and the null point
bull Should the upward pull of the uphill span becomes greater than downward load of the next adjacent span actual uplift will be caused and the conductor would tend to wing clear of the tower upwards
bull For any easy check of whether a tower is under uplift or not the following method may be adopted
bull The Template is applied horizontally until the tops of alternate supports coincide with the Cold Curve
bull If the support is under uplift and has to be extended so as to be above it and in case requisite standard body extension do not suffice for doing this tower which is designed to take uplift will have to be used
bull However for the stability of the line it is not desirable to place a tower in such a position where it is always under permanent uplift condition
bull In case it becomes mandatory due to route compulsion the cross‐arms of the tower subjected to up lift shall be designed to take the extra upward pull
bull The intermediate spans shall be as near as possible to the normal design span bull In case an individual span becomes too short on account of undulations in ground
profiles one or more line supports of the Section may be extended by inserting standard body extensions
bull Even if the line does not deviate for a long run sections have to be provided after every 12 to 15 tangent towers (ie 3 to 4 km length)
bull For this purpose a small angle tension tower designed for 15deg should only be used bull This is mandatory to afford better stability of the line against Transverse wind forces
and to facilitate easy stringing bull Besides 15deg angle tension tower is most economical amongst the standard angle tension
towers 29 Use of computer for preparing sag template and the tower spotting 291 Before taking up the tower design on hand Sag and Tension charts are required to be prepared These charts indicate the values of sag and tension of conductor and the earth wire at Maximum temperature minimum temperature and every‐day temperature under 10036(66) and 0 wind pressure Normally in plain terrain in India the maximum minimum and every‐day temperatures are considered as 0 DegC 75 Deg C and 32Deg C These values may change in the region experiencing snow or Sub‐Zero temperatures If the conductor is required to carry large block of power the maximum surface temperature of conductor can be taken up to 95Deg C For Earth wires the maximum temperature is taken as 53Deg C 292 Based on the sag tension charts the sag template curves can be plotted on the computer through a specific programme The full scale print out of the curves is then used to prepare the Acrylic Sag Template by itching process 210 Towers Spotting Data 2101 Since each tower is designed to withstand a definite load only in each of transverse vertical and longitudinal directions the surveyor must know these limitations for the various types of towers
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 4
by using GPS (Geographical Positioning System) The general points to be kept in view while establishing the preliminary route at the time of reconnaissance survey are as under a) The route should be as short and as straight as possible b) Where ever possible attempt should be made to lay the line near to or along roadway Alternatively the line should be approachable to the extent possible c) The number of angle towers should minimum and within these the number of heavier angle towers shall be as less as possible d) Cost of securing and clearing right of way (ROW) making access roads and time required for these works should be minimum e) Corridor through which line is taken should be free from Encumbrances such as non‐Agricultural land notified area Defense establishment oil amp gas establishment acquired mining areas etc f) Care is also required to be taken that the line route avoids any big planned development in the region such as Airport State Industrial Estate Mega Power Projects etc If this is not done shifting of the line may be required later or objection to the construction may occur g) Crossing with permanent objects such as Railway lines and roads should be made preferably at right angles h) In case of hilly terrain it is necessary to conduct detailed survey and locate the tower positions suitable to the topography Detailed survey is recommended for such terrain i) The reconnaissance survey will also establish if we can avoid the following
bull Marshy areas low lying lands river beds earth slip zones etc involving risk to stability of foundation amp the tower
bull Areas subjected to floods gushing ndash culverts during rainy seasons tanks ponds lakes snow blizzards
bull Inaccessible areas where approach roads are not possible bull Areas which will create problems of right of way and way leave bull Route involving abrupt changes in levels too many long spans river or power line crossings or
near parallelism to telecommunication lines bull Thick forest or areas involving heavy compensatory payments for the ROW
j) The reconnaissance survey is useful for collecting the first hand information about various important field data required for transmission line construction which are as under
bull Major power line crossing details (66 KV and above) bull Railway crossing details bull Major river crossing details bull Source of construction materials viz metal sand water etc along the line bull Important rail heads for the purpose of receipt of materials bull Important villages or Railway stations along the route for the purpose of selection of labor
camps bull Nature of soil strata likely to be encountered along the route and the terrain bull Availability of skilled semiskilled and un‐skilled labor their present rate on daily basis or on
contract basis bull Names of the major towns for the purpose of selection of site offices bull Likely local support or hindrance from various section of population along the route of the line
Power Consultants amp Agencies Page 5
For fixing the final alignment and angle points on the ground as per the reconnaissance survey route alignment survey shall be carried out with the help of Theodolite andor Total Station survey chainsmeasuring tapes etc 24 Detailed Survey 241 The main objective of carrying out detailed survey is to prepare longitudinal and cross section profiles on the approved route alignment and to prepare the route plan showing details of deviation angles important objects coming within the right of way and show the landmark pointsobjects along the route with their distance from the alignment of line Work of detailed survey is normally done in two stages
1 By actual field observation taking level readings and calculating distances level differences deflection angles offset distances etc
2 By plotting of profiles on graphed tracing papers of mm x mm size 242 The use of Total Station facilitates quick measurement of distance ground levels and the angles between the two reference points The Total Station is located at fixed point and there after the prism mounted in a stand is moved along the route of the line preferably at an interval of 20 metres Each reading gives the distance and level difference These readings are stored in the memory of Total Station (TS) The data is there after transferred to the computer 243 Field Observation Recording and Calculations 2431 The method of taking level readings for preparation of longitudinal and cross section profile can be one of the following
bull By chain and dumpy level bull By tachometric survey with Theodolite bull By using Total Station and the prism
First method is more useful in plain areas where chaining can be done easily with the help of semiskilled surveyors Tachometric method offers a great advantage in hilly regions and such other inaccessible places where chaining is not possible This method needs skilled surveyors having good understanding of the use of Theodolite and basic knowledge of trigonometry In this method both traversing and leveling is done by means of a tachometric Theodolite The horizontal and vertical distances are computed with the help of readings of the stadia wires taken on the staff held at the reading point The accuracy of the work will depend upon the quality and cost of the equipment The range of operation of Theodolite is much higher than the dumpy level The surveyor and his team will move on an approved route and take ground levels in the field book at an interval of 20 to 30 meters 2432 As stated in 242 above the Total Station is the most modern equipment for surveying It saves lot of time and the observations are highly accurate This equipment is very expensive and needs lot of precautions in handling If the length of line is very short Theodolite can also serve the purpose 25 Plotting of Profiles 251 From the field book entries route plan and longitudinal profile commonly referred to as ldquoroute profilerdquo or ldquosurvey chartrdquo is prepared in the drawing office These charts are prepared and plotted on 1mm5mm1cm square paper of formed drawing sheets of graphed tracing paper The scale normally preferred is 1200mm‐vertical 12000mm‐horizontal 252 The profile shall include the following
Power Consultants amp Agencies Page 6
bull The longitudinal profiles along the centre‐line of the transmission line route including the bottom conductor catenaries
bull The cross‐section profile wherever appreciable difference in level exists with references to centre‐line level In such cases the cross‐section levels shall be taken at each 50100m intervals
bull Route plan giving details of all objects lying within the right of way and just along the boundary of right of way
bull Angle of line deviation duly marked left (L) or right (R) as the case may be bull Objects and their distances along the route within the right of way from centre line nearby
villages important pucca roads amp or riverscanals cart tracks etc should be marked on the route profile
bull Crossing details with any other power or telecommunication lines roads railway lines canals or rivers should be marked as clearly as possible
bull Readings should be taken and charts should show levels of roads canal embankments maximum waterflood levels railway rail top levels heights of supportslines being crossed all trees coming within the clearance zone
bull It is advisable to prepare an independent route profile for Major River crossing section deploying tall special towers or normal towers on piles in the river crossing section as the river crossing is a special task in the construction process which involves special design
26 Tower Spotting 261 The work of tower spotting is a very precise job as it has an implication on overall cost After the tower designs are finalized the tower spotting chart or structure limitation charts are prepared Similarly the drawing of the sag template and its replica is prepared on Acrylic sheet Application of Sag Template helps to decide optimum tower position on Survey Chart which ultimately helps in finalizing the quantity of each type of tower and their extensions (3 meter amp 6 meter etc) 27 Preparation of Sag Template 271 Sag template is a very important tool for the surveyor by the help of which Tower spotting can be done Depending upon the maximum specified permissible temperature of the conductor and zero wind condition the ground clearance is to be maintained by the line Similarly under the specified minimum temperature of the conductor surface with zero wind condition the tower tensions should be within the specified limits The sag template curves are first prepared on tracing paper and the blue print is taken out from the tracing Their replicas on Acrylic sheets are prepared with the itching process The Acrylic sheets are normally 25 to 3 mm thick 272 The sag templates have the following curves itched on them
bull lsquoCold or Uplift Curversquo‐Showing sag of conductor at specified minimum temperature and zero wind
bull lsquoHotrsquo or lsquoMaximum Sag Curversquo showing maximum sag of conductor under zero wind and maximum temperature and sag tolerances are also allowed to take care of stringing error conductor creep or snow incidences
bull Ground clearance Curve‐Drawn parallel to hot curve and at a distance equal to specified minimum ground clearance
Power Consultants amp Agencies Page 7
bull Tower footing Curve‐For normal tower drawn parallel to hot curve under ground clearance curve and separated by a distance equal to maximum sag at design span
273 In erecting an overhead line all the spans cannot be kept equal to normal design span because of the profile of the ground and proper ground and object clearance considerations A constant tension is calculated which will be uniform throughout the Section (from one tension tower to other tension tower) however the sags in individual spans will vary according to their respective spans The lsquoCold and Hotrsquo Template Curves are plotted as parabola to the same scale as the survey chart for the minimum and maximum sags for the normal span (specified in the tender specifications)
28 Application of Sag Template for Tower Spotting 281 The Sag Template is an important tool for correct spotting of the towers after the detailed survey work is completed The following are the steps to be followed for correct application of sag template
bull The acrylic sag template is applied to the ground profile by moving the same horizontally while always ensuring that the vertical axis is held vertical with reference to graphed lines of the tracing paper below
bull The structure positions are marked where the tower footing curve just touches the profile while the ground clearance curve is just clear and above the profile to the left or right of the centre line up to a distance equal to maximum cross area spread on either side
bull Besides normal ground clearance the clearances between power conductor and objects like other power or telecommunication lines houses trolley wires roads railway tracks canal embankments etc shall be checked
bull Extra clearance can be obtained either by reducing the span or providing extension to tower body depending on which alternative is most economical
bull The weight span on either side of a tower can be easily obtained by marking the low points of sags (Null Point) in two adjacent spans and then reading the distance between the two
bull On inclined spans null point may be outside the span
Power Consultants amp Agencies Page 8
bull This indicates that the total weight of conductor is taken up by the higher tower and the lower tower is being pulled up by a force equal to the weight of conductor between lower support and the null point
bull Should the upward pull of the uphill span becomes greater than downward load of the next adjacent span actual uplift will be caused and the conductor would tend to wing clear of the tower upwards
bull For any easy check of whether a tower is under uplift or not the following method may be adopted
bull The Template is applied horizontally until the tops of alternate supports coincide with the Cold Curve
bull If the support is under uplift and has to be extended so as to be above it and in case requisite standard body extension do not suffice for doing this tower which is designed to take uplift will have to be used
bull However for the stability of the line it is not desirable to place a tower in such a position where it is always under permanent uplift condition
bull In case it becomes mandatory due to route compulsion the cross‐arms of the tower subjected to up lift shall be designed to take the extra upward pull
bull The intermediate spans shall be as near as possible to the normal design span bull In case an individual span becomes too short on account of undulations in ground
profiles one or more line supports of the Section may be extended by inserting standard body extensions
bull Even if the line does not deviate for a long run sections have to be provided after every 12 to 15 tangent towers (ie 3 to 4 km length)
bull For this purpose a small angle tension tower designed for 15deg should only be used bull This is mandatory to afford better stability of the line against Transverse wind forces
and to facilitate easy stringing bull Besides 15deg angle tension tower is most economical amongst the standard angle tension
towers 29 Use of computer for preparing sag template and the tower spotting 291 Before taking up the tower design on hand Sag and Tension charts are required to be prepared These charts indicate the values of sag and tension of conductor and the earth wire at Maximum temperature minimum temperature and every‐day temperature under 10036(66) and 0 wind pressure Normally in plain terrain in India the maximum minimum and every‐day temperatures are considered as 0 DegC 75 Deg C and 32Deg C These values may change in the region experiencing snow or Sub‐Zero temperatures If the conductor is required to carry large block of power the maximum surface temperature of conductor can be taken up to 95Deg C For Earth wires the maximum temperature is taken as 53Deg C 292 Based on the sag tension charts the sag template curves can be plotted on the computer through a specific programme The full scale print out of the curves is then used to prepare the Acrylic Sag Template by itching process 210 Towers Spotting Data 2101 Since each tower is designed to withstand a definite load only in each of transverse vertical and longitudinal directions the surveyor must know these limitations for the various types of towers
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 5
For fixing the final alignment and angle points on the ground as per the reconnaissance survey route alignment survey shall be carried out with the help of Theodolite andor Total Station survey chainsmeasuring tapes etc 24 Detailed Survey 241 The main objective of carrying out detailed survey is to prepare longitudinal and cross section profiles on the approved route alignment and to prepare the route plan showing details of deviation angles important objects coming within the right of way and show the landmark pointsobjects along the route with their distance from the alignment of line Work of detailed survey is normally done in two stages
1 By actual field observation taking level readings and calculating distances level differences deflection angles offset distances etc
2 By plotting of profiles on graphed tracing papers of mm x mm size 242 The use of Total Station facilitates quick measurement of distance ground levels and the angles between the two reference points The Total Station is located at fixed point and there after the prism mounted in a stand is moved along the route of the line preferably at an interval of 20 metres Each reading gives the distance and level difference These readings are stored in the memory of Total Station (TS) The data is there after transferred to the computer 243 Field Observation Recording and Calculations 2431 The method of taking level readings for preparation of longitudinal and cross section profile can be one of the following
bull By chain and dumpy level bull By tachometric survey with Theodolite bull By using Total Station and the prism
First method is more useful in plain areas where chaining can be done easily with the help of semiskilled surveyors Tachometric method offers a great advantage in hilly regions and such other inaccessible places where chaining is not possible This method needs skilled surveyors having good understanding of the use of Theodolite and basic knowledge of trigonometry In this method both traversing and leveling is done by means of a tachometric Theodolite The horizontal and vertical distances are computed with the help of readings of the stadia wires taken on the staff held at the reading point The accuracy of the work will depend upon the quality and cost of the equipment The range of operation of Theodolite is much higher than the dumpy level The surveyor and his team will move on an approved route and take ground levels in the field book at an interval of 20 to 30 meters 2432 As stated in 242 above the Total Station is the most modern equipment for surveying It saves lot of time and the observations are highly accurate This equipment is very expensive and needs lot of precautions in handling If the length of line is very short Theodolite can also serve the purpose 25 Plotting of Profiles 251 From the field book entries route plan and longitudinal profile commonly referred to as ldquoroute profilerdquo or ldquosurvey chartrdquo is prepared in the drawing office These charts are prepared and plotted on 1mm5mm1cm square paper of formed drawing sheets of graphed tracing paper The scale normally preferred is 1200mm‐vertical 12000mm‐horizontal 252 The profile shall include the following
Power Consultants amp Agencies Page 6
bull The longitudinal profiles along the centre‐line of the transmission line route including the bottom conductor catenaries
bull The cross‐section profile wherever appreciable difference in level exists with references to centre‐line level In such cases the cross‐section levels shall be taken at each 50100m intervals
bull Route plan giving details of all objects lying within the right of way and just along the boundary of right of way
bull Angle of line deviation duly marked left (L) or right (R) as the case may be bull Objects and their distances along the route within the right of way from centre line nearby
villages important pucca roads amp or riverscanals cart tracks etc should be marked on the route profile
bull Crossing details with any other power or telecommunication lines roads railway lines canals or rivers should be marked as clearly as possible
bull Readings should be taken and charts should show levels of roads canal embankments maximum waterflood levels railway rail top levels heights of supportslines being crossed all trees coming within the clearance zone
bull It is advisable to prepare an independent route profile for Major River crossing section deploying tall special towers or normal towers on piles in the river crossing section as the river crossing is a special task in the construction process which involves special design
26 Tower Spotting 261 The work of tower spotting is a very precise job as it has an implication on overall cost After the tower designs are finalized the tower spotting chart or structure limitation charts are prepared Similarly the drawing of the sag template and its replica is prepared on Acrylic sheet Application of Sag Template helps to decide optimum tower position on Survey Chart which ultimately helps in finalizing the quantity of each type of tower and their extensions (3 meter amp 6 meter etc) 27 Preparation of Sag Template 271 Sag template is a very important tool for the surveyor by the help of which Tower spotting can be done Depending upon the maximum specified permissible temperature of the conductor and zero wind condition the ground clearance is to be maintained by the line Similarly under the specified minimum temperature of the conductor surface with zero wind condition the tower tensions should be within the specified limits The sag template curves are first prepared on tracing paper and the blue print is taken out from the tracing Their replicas on Acrylic sheets are prepared with the itching process The Acrylic sheets are normally 25 to 3 mm thick 272 The sag templates have the following curves itched on them
bull lsquoCold or Uplift Curversquo‐Showing sag of conductor at specified minimum temperature and zero wind
bull lsquoHotrsquo or lsquoMaximum Sag Curversquo showing maximum sag of conductor under zero wind and maximum temperature and sag tolerances are also allowed to take care of stringing error conductor creep or snow incidences
bull Ground clearance Curve‐Drawn parallel to hot curve and at a distance equal to specified minimum ground clearance
Power Consultants amp Agencies Page 7
bull Tower footing Curve‐For normal tower drawn parallel to hot curve under ground clearance curve and separated by a distance equal to maximum sag at design span
273 In erecting an overhead line all the spans cannot be kept equal to normal design span because of the profile of the ground and proper ground and object clearance considerations A constant tension is calculated which will be uniform throughout the Section (from one tension tower to other tension tower) however the sags in individual spans will vary according to their respective spans The lsquoCold and Hotrsquo Template Curves are plotted as parabola to the same scale as the survey chart for the minimum and maximum sags for the normal span (specified in the tender specifications)
28 Application of Sag Template for Tower Spotting 281 The Sag Template is an important tool for correct spotting of the towers after the detailed survey work is completed The following are the steps to be followed for correct application of sag template
bull The acrylic sag template is applied to the ground profile by moving the same horizontally while always ensuring that the vertical axis is held vertical with reference to graphed lines of the tracing paper below
bull The structure positions are marked where the tower footing curve just touches the profile while the ground clearance curve is just clear and above the profile to the left or right of the centre line up to a distance equal to maximum cross area spread on either side
bull Besides normal ground clearance the clearances between power conductor and objects like other power or telecommunication lines houses trolley wires roads railway tracks canal embankments etc shall be checked
bull Extra clearance can be obtained either by reducing the span or providing extension to tower body depending on which alternative is most economical
bull The weight span on either side of a tower can be easily obtained by marking the low points of sags (Null Point) in two adjacent spans and then reading the distance between the two
bull On inclined spans null point may be outside the span
Power Consultants amp Agencies Page 8
bull This indicates that the total weight of conductor is taken up by the higher tower and the lower tower is being pulled up by a force equal to the weight of conductor between lower support and the null point
bull Should the upward pull of the uphill span becomes greater than downward load of the next adjacent span actual uplift will be caused and the conductor would tend to wing clear of the tower upwards
bull For any easy check of whether a tower is under uplift or not the following method may be adopted
bull The Template is applied horizontally until the tops of alternate supports coincide with the Cold Curve
bull If the support is under uplift and has to be extended so as to be above it and in case requisite standard body extension do not suffice for doing this tower which is designed to take uplift will have to be used
bull However for the stability of the line it is not desirable to place a tower in such a position where it is always under permanent uplift condition
bull In case it becomes mandatory due to route compulsion the cross‐arms of the tower subjected to up lift shall be designed to take the extra upward pull
bull The intermediate spans shall be as near as possible to the normal design span bull In case an individual span becomes too short on account of undulations in ground
profiles one or more line supports of the Section may be extended by inserting standard body extensions
bull Even if the line does not deviate for a long run sections have to be provided after every 12 to 15 tangent towers (ie 3 to 4 km length)
bull For this purpose a small angle tension tower designed for 15deg should only be used bull This is mandatory to afford better stability of the line against Transverse wind forces
and to facilitate easy stringing bull Besides 15deg angle tension tower is most economical amongst the standard angle tension
towers 29 Use of computer for preparing sag template and the tower spotting 291 Before taking up the tower design on hand Sag and Tension charts are required to be prepared These charts indicate the values of sag and tension of conductor and the earth wire at Maximum temperature minimum temperature and every‐day temperature under 10036(66) and 0 wind pressure Normally in plain terrain in India the maximum minimum and every‐day temperatures are considered as 0 DegC 75 Deg C and 32Deg C These values may change in the region experiencing snow or Sub‐Zero temperatures If the conductor is required to carry large block of power the maximum surface temperature of conductor can be taken up to 95Deg C For Earth wires the maximum temperature is taken as 53Deg C 292 Based on the sag tension charts the sag template curves can be plotted on the computer through a specific programme The full scale print out of the curves is then used to prepare the Acrylic Sag Template by itching process 210 Towers Spotting Data 2101 Since each tower is designed to withstand a definite load only in each of transverse vertical and longitudinal directions the surveyor must know these limitations for the various types of towers
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 6
bull The longitudinal profiles along the centre‐line of the transmission line route including the bottom conductor catenaries
bull The cross‐section profile wherever appreciable difference in level exists with references to centre‐line level In such cases the cross‐section levels shall be taken at each 50100m intervals
bull Route plan giving details of all objects lying within the right of way and just along the boundary of right of way
bull Angle of line deviation duly marked left (L) or right (R) as the case may be bull Objects and their distances along the route within the right of way from centre line nearby
villages important pucca roads amp or riverscanals cart tracks etc should be marked on the route profile
bull Crossing details with any other power or telecommunication lines roads railway lines canals or rivers should be marked as clearly as possible
bull Readings should be taken and charts should show levels of roads canal embankments maximum waterflood levels railway rail top levels heights of supportslines being crossed all trees coming within the clearance zone
bull It is advisable to prepare an independent route profile for Major River crossing section deploying tall special towers or normal towers on piles in the river crossing section as the river crossing is a special task in the construction process which involves special design
26 Tower Spotting 261 The work of tower spotting is a very precise job as it has an implication on overall cost After the tower designs are finalized the tower spotting chart or structure limitation charts are prepared Similarly the drawing of the sag template and its replica is prepared on Acrylic sheet Application of Sag Template helps to decide optimum tower position on Survey Chart which ultimately helps in finalizing the quantity of each type of tower and their extensions (3 meter amp 6 meter etc) 27 Preparation of Sag Template 271 Sag template is a very important tool for the surveyor by the help of which Tower spotting can be done Depending upon the maximum specified permissible temperature of the conductor and zero wind condition the ground clearance is to be maintained by the line Similarly under the specified minimum temperature of the conductor surface with zero wind condition the tower tensions should be within the specified limits The sag template curves are first prepared on tracing paper and the blue print is taken out from the tracing Their replicas on Acrylic sheets are prepared with the itching process The Acrylic sheets are normally 25 to 3 mm thick 272 The sag templates have the following curves itched on them
bull lsquoCold or Uplift Curversquo‐Showing sag of conductor at specified minimum temperature and zero wind
bull lsquoHotrsquo or lsquoMaximum Sag Curversquo showing maximum sag of conductor under zero wind and maximum temperature and sag tolerances are also allowed to take care of stringing error conductor creep or snow incidences
bull Ground clearance Curve‐Drawn parallel to hot curve and at a distance equal to specified minimum ground clearance
Power Consultants amp Agencies Page 7
bull Tower footing Curve‐For normal tower drawn parallel to hot curve under ground clearance curve and separated by a distance equal to maximum sag at design span
273 In erecting an overhead line all the spans cannot be kept equal to normal design span because of the profile of the ground and proper ground and object clearance considerations A constant tension is calculated which will be uniform throughout the Section (from one tension tower to other tension tower) however the sags in individual spans will vary according to their respective spans The lsquoCold and Hotrsquo Template Curves are plotted as parabola to the same scale as the survey chart for the minimum and maximum sags for the normal span (specified in the tender specifications)
28 Application of Sag Template for Tower Spotting 281 The Sag Template is an important tool for correct spotting of the towers after the detailed survey work is completed The following are the steps to be followed for correct application of sag template
bull The acrylic sag template is applied to the ground profile by moving the same horizontally while always ensuring that the vertical axis is held vertical with reference to graphed lines of the tracing paper below
bull The structure positions are marked where the tower footing curve just touches the profile while the ground clearance curve is just clear and above the profile to the left or right of the centre line up to a distance equal to maximum cross area spread on either side
bull Besides normal ground clearance the clearances between power conductor and objects like other power or telecommunication lines houses trolley wires roads railway tracks canal embankments etc shall be checked
bull Extra clearance can be obtained either by reducing the span or providing extension to tower body depending on which alternative is most economical
bull The weight span on either side of a tower can be easily obtained by marking the low points of sags (Null Point) in two adjacent spans and then reading the distance between the two
bull On inclined spans null point may be outside the span
Power Consultants amp Agencies Page 8
bull This indicates that the total weight of conductor is taken up by the higher tower and the lower tower is being pulled up by a force equal to the weight of conductor between lower support and the null point
bull Should the upward pull of the uphill span becomes greater than downward load of the next adjacent span actual uplift will be caused and the conductor would tend to wing clear of the tower upwards
bull For any easy check of whether a tower is under uplift or not the following method may be adopted
bull The Template is applied horizontally until the tops of alternate supports coincide with the Cold Curve
bull If the support is under uplift and has to be extended so as to be above it and in case requisite standard body extension do not suffice for doing this tower which is designed to take uplift will have to be used
bull However for the stability of the line it is not desirable to place a tower in such a position where it is always under permanent uplift condition
bull In case it becomes mandatory due to route compulsion the cross‐arms of the tower subjected to up lift shall be designed to take the extra upward pull
bull The intermediate spans shall be as near as possible to the normal design span bull In case an individual span becomes too short on account of undulations in ground
profiles one or more line supports of the Section may be extended by inserting standard body extensions
bull Even if the line does not deviate for a long run sections have to be provided after every 12 to 15 tangent towers (ie 3 to 4 km length)
bull For this purpose a small angle tension tower designed for 15deg should only be used bull This is mandatory to afford better stability of the line against Transverse wind forces
and to facilitate easy stringing bull Besides 15deg angle tension tower is most economical amongst the standard angle tension
towers 29 Use of computer for preparing sag template and the tower spotting 291 Before taking up the tower design on hand Sag and Tension charts are required to be prepared These charts indicate the values of sag and tension of conductor and the earth wire at Maximum temperature minimum temperature and every‐day temperature under 10036(66) and 0 wind pressure Normally in plain terrain in India the maximum minimum and every‐day temperatures are considered as 0 DegC 75 Deg C and 32Deg C These values may change in the region experiencing snow or Sub‐Zero temperatures If the conductor is required to carry large block of power the maximum surface temperature of conductor can be taken up to 95Deg C For Earth wires the maximum temperature is taken as 53Deg C 292 Based on the sag tension charts the sag template curves can be plotted on the computer through a specific programme The full scale print out of the curves is then used to prepare the Acrylic Sag Template by itching process 210 Towers Spotting Data 2101 Since each tower is designed to withstand a definite load only in each of transverse vertical and longitudinal directions the surveyor must know these limitations for the various types of towers
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 7
bull Tower footing Curve‐For normal tower drawn parallel to hot curve under ground clearance curve and separated by a distance equal to maximum sag at design span
273 In erecting an overhead line all the spans cannot be kept equal to normal design span because of the profile of the ground and proper ground and object clearance considerations A constant tension is calculated which will be uniform throughout the Section (from one tension tower to other tension tower) however the sags in individual spans will vary according to their respective spans The lsquoCold and Hotrsquo Template Curves are plotted as parabola to the same scale as the survey chart for the minimum and maximum sags for the normal span (specified in the tender specifications)
28 Application of Sag Template for Tower Spotting 281 The Sag Template is an important tool for correct spotting of the towers after the detailed survey work is completed The following are the steps to be followed for correct application of sag template
bull The acrylic sag template is applied to the ground profile by moving the same horizontally while always ensuring that the vertical axis is held vertical with reference to graphed lines of the tracing paper below
bull The structure positions are marked where the tower footing curve just touches the profile while the ground clearance curve is just clear and above the profile to the left or right of the centre line up to a distance equal to maximum cross area spread on either side
bull Besides normal ground clearance the clearances between power conductor and objects like other power or telecommunication lines houses trolley wires roads railway tracks canal embankments etc shall be checked
bull Extra clearance can be obtained either by reducing the span or providing extension to tower body depending on which alternative is most economical
bull The weight span on either side of a tower can be easily obtained by marking the low points of sags (Null Point) in two adjacent spans and then reading the distance between the two
bull On inclined spans null point may be outside the span
Power Consultants amp Agencies Page 8
bull This indicates that the total weight of conductor is taken up by the higher tower and the lower tower is being pulled up by a force equal to the weight of conductor between lower support and the null point
bull Should the upward pull of the uphill span becomes greater than downward load of the next adjacent span actual uplift will be caused and the conductor would tend to wing clear of the tower upwards
bull For any easy check of whether a tower is under uplift or not the following method may be adopted
bull The Template is applied horizontally until the tops of alternate supports coincide with the Cold Curve
bull If the support is under uplift and has to be extended so as to be above it and in case requisite standard body extension do not suffice for doing this tower which is designed to take uplift will have to be used
bull However for the stability of the line it is not desirable to place a tower in such a position where it is always under permanent uplift condition
bull In case it becomes mandatory due to route compulsion the cross‐arms of the tower subjected to up lift shall be designed to take the extra upward pull
bull The intermediate spans shall be as near as possible to the normal design span bull In case an individual span becomes too short on account of undulations in ground
profiles one or more line supports of the Section may be extended by inserting standard body extensions
bull Even if the line does not deviate for a long run sections have to be provided after every 12 to 15 tangent towers (ie 3 to 4 km length)
bull For this purpose a small angle tension tower designed for 15deg should only be used bull This is mandatory to afford better stability of the line against Transverse wind forces
and to facilitate easy stringing bull Besides 15deg angle tension tower is most economical amongst the standard angle tension
towers 29 Use of computer for preparing sag template and the tower spotting 291 Before taking up the tower design on hand Sag and Tension charts are required to be prepared These charts indicate the values of sag and tension of conductor and the earth wire at Maximum temperature minimum temperature and every‐day temperature under 10036(66) and 0 wind pressure Normally in plain terrain in India the maximum minimum and every‐day temperatures are considered as 0 DegC 75 Deg C and 32Deg C These values may change in the region experiencing snow or Sub‐Zero temperatures If the conductor is required to carry large block of power the maximum surface temperature of conductor can be taken up to 95Deg C For Earth wires the maximum temperature is taken as 53Deg C 292 Based on the sag tension charts the sag template curves can be plotted on the computer through a specific programme The full scale print out of the curves is then used to prepare the Acrylic Sag Template by itching process 210 Towers Spotting Data 2101 Since each tower is designed to withstand a definite load only in each of transverse vertical and longitudinal directions the surveyor must know these limitations for the various types of towers
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
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joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
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corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
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35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
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For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 8
bull This indicates that the total weight of conductor is taken up by the higher tower and the lower tower is being pulled up by a force equal to the weight of conductor between lower support and the null point
bull Should the upward pull of the uphill span becomes greater than downward load of the next adjacent span actual uplift will be caused and the conductor would tend to wing clear of the tower upwards
bull For any easy check of whether a tower is under uplift or not the following method may be adopted
bull The Template is applied horizontally until the tops of alternate supports coincide with the Cold Curve
bull If the support is under uplift and has to be extended so as to be above it and in case requisite standard body extension do not suffice for doing this tower which is designed to take uplift will have to be used
bull However for the stability of the line it is not desirable to place a tower in such a position where it is always under permanent uplift condition
bull In case it becomes mandatory due to route compulsion the cross‐arms of the tower subjected to up lift shall be designed to take the extra upward pull
bull The intermediate spans shall be as near as possible to the normal design span bull In case an individual span becomes too short on account of undulations in ground
profiles one or more line supports of the Section may be extended by inserting standard body extensions
bull Even if the line does not deviate for a long run sections have to be provided after every 12 to 15 tangent towers (ie 3 to 4 km length)
bull For this purpose a small angle tension tower designed for 15deg should only be used bull This is mandatory to afford better stability of the line against Transverse wind forces
and to facilitate easy stringing bull Besides 15deg angle tension tower is most economical amongst the standard angle tension
towers 29 Use of computer for preparing sag template and the tower spotting 291 Before taking up the tower design on hand Sag and Tension charts are required to be prepared These charts indicate the values of sag and tension of conductor and the earth wire at Maximum temperature minimum temperature and every‐day temperature under 10036(66) and 0 wind pressure Normally in plain terrain in India the maximum minimum and every‐day temperatures are considered as 0 DegC 75 Deg C and 32Deg C These values may change in the region experiencing snow or Sub‐Zero temperatures If the conductor is required to carry large block of power the maximum surface temperature of conductor can be taken up to 95Deg C For Earth wires the maximum temperature is taken as 53Deg C 292 Based on the sag tension charts the sag template curves can be plotted on the computer through a specific programme The full scale print out of the curves is then used to prepare the Acrylic Sag Template by itching process 210 Towers Spotting Data 2101 Since each tower is designed to withstand a definite load only in each of transverse vertical and longitudinal directions the surveyor must know these limitations for the various types of towers
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 9
available for use on line so than he can spot an appropriate type of tower structures along the route These limits are given in a chart form called lsquoStructure Limitation Chart or ldquoTower Spotting Datardquo which is prepared by the design department of the utility contractor These charts define the limits for permissible ruling span weight span wind span individual span and the degree of the deviation allowed on each of the standard towers These charts are made for normal towers only
For all special crossings individual tower checking is essential by the design department These charts also indicate the additional angle of deviation which can be allowed in the tower by limiting the spans so that the design load limits of the tower are not exceeded
TOWER SPOTTING
V-1 200H-1 2000
SCALE DRAWING NO REV
0A
Title CLIENT - Project
TOWER SPOTTING amp SAG CURVE OF 400kV DC TRANSMISSIONLINE
DATUM 2620m
AP4
8 - C
H5
3612
02m
AP4
9 - C
H5
4867
67m
PROPOSED SUB STATION
AP-45(14deg4823)R AP-46(75deg4341)L
422
41166
422
A 198 VISHVAMITRY TOWNSHIP OPP GUJARAT TRACTORSVADODARA - 390 011 Ph(0265) 2343001 Fax(0265) 2356291E-mail smtakalkarpowerconsultantinfo smtakalkarpcagmailcomWeb wwwpowerconsultantinfo
POWER CONSULTANTS amp AGENCIESCONSULTANT -
CUMULATIVE
LEVELS(M)REDUCED
DETAILS
amp INTERFERENCECROSSING
CHAINAGES(M)
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
+3M
+6M
+9M
Ground Clearanceat 1326 Mtr
Conductor stringingpoint at 2221 Mtr
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Hot Curve 85deg C
Ground Clearance Curve
Cold Curve 0deg C
Cold Curve 0deg C
Cold Curve 0deg C
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2058321141683
42716206462207
43112072622384
DA+6451
157
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
2112058341683
41948214282052
42341219012044
DA+3452
158
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
00000211211
207720000020772
202990000020299
DD+0460
159
Wind Span
TL R
Weight Span (Cold)L R
T
Weight Span (Hot)L R
T
Loc No-
211211422
41336201321206
411821981621366
DB+3450
156
COMPAQ
COMPAQ
Tower Spottingdwg
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 10
211 Preparation of Tower Schedule 2111 In order to decide the tower type for a particular location following information is required from the design department
bull Angle of line deviation on tower bull Whether it is to be used as section tower or dead end tower bull Sum of adjacent spans bull Weight span on tower bull Whether an immediate lower size of tower can be used in place of the actual angle tower by
limiting the span bull Whether a river can be crossed using normal tower withwithout extensions or by providing
special tower or by locating towers in mid stream by providing the pile foundations bull Whether a hill side extension will be required
212 Check Survey 2121 Check survey is carried out for the following
bull To reconfirm the work carried out during detailed survey bull To locate and peg mark the tower position on ground corresponding to the route profiles bull To give direction pegs
213 Checking and Line Alignment 2131 In this operation traversing is done from the known fixed angle point (the starting point or any other obligatory point fixed by the purchaser) in the direction of given line deviation and up to a distance equal to the section length between the starting point and the next angle point If next angle point is firmly marked in field by means of a permanent peg mark (concrete burjee) then the closing error is noted both in longitudinal and transverse directions If the error is within 1 of the total section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart 2132 If the second angle point reached is not marked in field by the detailed survey gang (or the mark is missing) the angle point is tentatively fixed at the place reached as per deviation angle at starting point and first sectional length and line alignment is carried to the next deviation angle and next section length as per survey chart This process is continued till an angle point is reached which is fixed in field either by a permanent burjee (pillar) or by means of identification marks given in survey charts Intermediate checks can also be made by measuring offsets from the line to well defined objects are shown in survey charts very accurately (but much reliance cannot be given for correct alignment based on offset distance) 2133 These objects only guide the surveyor in moving as closely on the correct alignment as possible If the time span between the detailed survey and the check survey is too long care is required to keep the proper track of the original profile bench mark and offset distances Once the known angle point is reached then closing error is judiciously distributed in all the previous temporary sections and all angle points are finally marked on ground by means of concrete pillars Once the angle points are marked correct angle of deviation and section length are measured and noted on survey charts 214 Spotting and Peg Marking of Tower Locations 2141 Once each angle is fixed in field by the help of permanent concrete burjees and exact section length is known the surveyor proceeds to mark all intermediate tower positions on the straight line
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 11
joining the two angle points spaced at distance equal to individual span length as given on survey chart and after the same is duly adjusted for the closing error
bull In order to achieve correct alignment of all the intermediate towers between two angle points a number of alignment pegs are driven at the time of exact distance measurement of the section
bull The more the number of alignment pegs the better it will be for the readings as instrument errors are less if similar distances are measured in one reading
bull These pegs are also very useful when main tower marking burjees are found missing at a later date (due to mischief of local people or negligence of excavation marking gang or any other reason)
30 Foundation Work 31 After the survey work is over the activity of foundation is taken on hand The foundation work mainly includes Pit marking Excavation Stub setting Concreting Back filling and Curing They are described in brief as under 32 Directional Peg Marking for Excavation Pit Marking 321 Before the activity of excavation is taken up it essential to accurately mark the centre point of the tower centre point of each leg of the tower and the periphery of pit to be excavated for each leg foundation This is described in brief as under
bull Directional pegs are essential for correct alignment of tower centre line along longitudinal and transverse directions
bull On suspension tower pegs are set along the centre line of route alignment and perpendicular to it
bull On angle towers these are rotated by an angle equal to half the angle of line deviation and then the perpendiculars are marked
COMPAQ
ALLIGNMENT OF TRANSMISSION LINEdwg
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 12
33 PreparationStudy of Excavation Plan Suitable For the Proposed Type of Foundation 331 Trial Pit At the location of the tower a trial pit shall be made within the base of the proposed tower width This shall be generally 1 x 1 x 3 m size 332 Examination of trial pit The soil strata will be examined by EIC or an expert nominated by him who has expertise in the matter of soil classification The detailed examination report of the trial pit will be made then 333 Decision for type of foundation The EIC or the authorized engineer of the purchaser and the engineer of the contractor shall then decide upon the type of foundation to be adopted for that particular location Normally the design department contractor is equipped with the set of foundation design and the excavation plan for standard type of soils rocks and their combinations including sub‐ soil water bound strata Any one of the readily available foundation design for the particular type of tower which fits in to the classification of soilrock should be adopted If the strata are too strange special type of foundation has to be adopted with the approval of Design department of the purchaser There are many types of tower foundation which are in vogue these days They also relate to various types of soil classification such as normal soil clayey soil hard rock soft rock deformated soil etc The pile type amp well type foundations are generally used in river crossing and crossing sections of the line Plate type and grill type foundations are not being used these days as their reliability is low The type foundations can be used for smaller towers
34 Excavation 341 Pit marketing shall be carried out according to pit marking chart The pit size in the case of open cast foundations shall be determined after allowing a margin of 150mm round No margin is necessary in the case of undercut foundations The depth of the excavation at the pit enter shall be measured with reference to the tower center level The design office will furnish the survey gang with an lsquoExcavation pit Marking Chartrsquo or lsquoExcavation Planrsquo which gives distance of pit centers sides and
Power Consultants amp Agencies Page 13
corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
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corners with reference to center point of the tower These distances are measured and each pit boundary is marked in the field by means of chalk spade or pick axe along the side of the pits While excavating care should be taken that earth is cut verticallytaperedin steps as per the site requirement to avoid any mishap during the course of excavation and foundation work 342 Actual excavation Before commencement of the excavation work corrected and applicable excavation plan in accordance with the soilrock classification should be obtained by the construction crew members The excavation wall shall be vertical and the pit dimensions shall be strictly as per the excavation plan and foundation drawing All excavation shall be protected so as to maintain a clean surface until the footing is placed In case of collapsible soil precaution should be taken by providing shuttering and supports for the safety of the crew members
Various types of foundations used for tower are shown here under
TYPES amp SHAPES OF FOUNDATION
COMPAQ
COMPAQ
TYPES amp SHAPES OF FOUNDATIONSdwg
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 14
35 Classification of Soil 351 Normal Soil Soil which can be removed by an ordinary pick axe spade and shovel easily 352 Wet Soil (Submerged Soil) Where the subsoil water table is encountered within the range of foundation depth orand where pumping or bailing out of water is required due to presence of surface water will be treated as wet soilsubmerged soil 353 Rocky Soil (Strata) 3531 Fissured RockSoft Rock Lime stone laterite hard conglomerate or other soft or fissured rock which can be quarried or split with crow bars wedges or pickaxes will be classified as fissured rocksoft rock However if required light blasting may be resorted to for loosening the material and hasten the excavation activity However this will not in any way entitle the material to be classified as hard rock 3532 Hard Rock Any rock excavation other than specified under fissured rocksoft rock above for which blasting drilling chiseling are required Where the soil is of composite nature classification of foundation will be according to the type of soil which is predominant in the footing The decision of the Engineer‐in‐charge shall be final and binding with reference to classification of soil and foundation to be adopted at that particular location The adoption of footing depends upon the type of Soil and the tower loadings The foundation to be adopted therefore depends upon the type of soil quantum of tower loading and preference for structural arrangements of footing 36 Hard Rock Excavation Where rock is encountered the holes for tower footings shall preferably be drilled but where blasting is to be resorted to as an economy measure it shall be done with the utmost care to minimize the use of concrete for filling up the blasted area All necessary precautions for handling and use of blasting materials shall be taken If inadvertently large quantities are excavated blasted the full volume excavatedblasted shall be filled with the structural concrete If this is not adhered to there are chances of reduction of reliability of foundation against upward loads In case where drilling is done the stubs may be shortened suitably with the approval of the owner or his authorized representatives The excavation shall be carried out strictly as per the excavation plan approved by the ownercustomer for the particular type of structure withwithout extension and the particular type of Soil Rock However while re‐working the CC distance between the two pits will be with reference to the junction of reduced chimney and footing 37 Blasting Material The Contractor shall procure requisite blasting material and be responsible for the purpose of the storage and use of this material Necessary permissionapprovals from the concerned Government department may be obtained by the contractor 38 Shoring and Shuttering If pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pit collapse shoring and shuttering made out of timber planks of 30‐35mm
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 15
thickness or steel frames of adequate strength to suit the requirement will be provided Sand beddingstone bedding will be provided in foundation of marshy and wet black cotton foundations which will work as a sub‐grade 39 Dewatering Dewatering shall be carried out manually or by mechanical means or power driven pumps to facilitate excavation and casting of foundation The pumps shall be suitable for handling muddy water Dewatering is not necessary in case of bored foundations extending below water table The size of the mechanicalelectrical pump will depend upon the quantum of water required to be handled per hour In areas where sub‐soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water In this system a grid of pipes are laid around the area where the pits are excavated and the system is very effective in pumping water particularly in sandy soils After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth 310 Setting of Stubs The stubs shall be set correctly in accordance with approved method at the exact location and alignment and precisely at correct levels with the help of stub setting templates and leveling instrument Stubs shall be set in the Presence of Ownerrsquos representative available at site where required The stubs are set in such a manner that the distance between the Stubs the alignment and slope are as per the approved misfit and design so as to permit assembling of the superstructure without undue pre‐stress strain or distortion in any part of the structure There are three methods by which this is generally accomplished
bull Use of combined Stub‐setting Template for all the four stubs of the tower including extension portions
bull Use of individual Leg Template for each stub bull Use as a Template the lowermost tower section or extension where Stub‐setting Template is
not available The first method is the most commonly used
bull The Stub‐setting Template comprises a light rigid square framework which holds the four stubs at the correct alignment and slope in four corners
bull The Stub‐setting Template generally of adjustable type which can suit the standard tower as well as towers with standard extensions of 3 meter amp 6 meter height
bull The Template is centered and leveled by sighting through transit bull The anchors or stubs are bolted to this Template one at each corner of the Template and are
held in their proper position until the concrete is poured and gets hardened The second method is adopted for casting the foundation locations having individual leg extensions or locations having broad base of Tower
bull In such case it is not possible to use the four legged stub setting template for various reasons related to design and construction
bull The answer to this problem is individual leg stub‐setting template bull The individual Leg Template comprises a steel channel or joist having a length more than the
size of the pit by about 2 to 3 meters bull A chamfered cleat is welded in centre of the channeljoist to provide the slope to the stub
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
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3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 16
bull The stub is bolted to the cleat of the Template with holes as required for the slop of the stub is provided
bull The individual Leg Templates are initially set on each pit approximately to the required position with reference to the centre point of the tower and with the help of a Theodolite (or Total Station) Dumpy level and a measuring tape before fixing form boxes and pouring concrete
bull The other version of individual leg extension is cut corner sections of conventional stub‐setting template
bull This is easy to fabricate and deploy at site bull This type of Template are very useful for casting the foundations of individual leg extensions in
which the foundation pits are staggered and use of either a normal Stub‐setting Template or the first section of the tower is not feasible
In the third method lower section of the tower or extension is used for setting stub bull In this method two opposite sides of the lower section of the tower are assembled horizontally
on the ground and the stubs are bolted to the same with correct slope and alignment bull Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the
four pits excavated at four corners of the tower to their proper size and depth bull The assembly is lifted in such a manner that stubs are not damaged bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals bull Then the assembled section is lined up made square with line and level after the proper
elevation and leveling have been done the bolts are tightened to make the frame as rigid as is reasonably possible
bull Thereafter the form boxes for foundations are built and the concrete is poured bull For heavy towers use of this method is not recommended bull For heavy towers use of Stub‐setting Template is recommended as propping jacking leveling
etc will be very difficult
COMPAQ
CUNSTRUCTION OF UNEQUAL LEG EXTENTIONSdwg
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 17
311 Mixing Placing and Compacting Of Concrete It is normal practice to use coarse and fine aggregates available along the line route andof nearest locations to the route so as to have economy and better progress Ordinary plain or reinforced cement concrete given in IS 456‐1978 shall be used in overhead line foundations For main foundation M15 or 124 mix cement concrete shall be used For lean concrete sub basis or pads M 10 or 136 mix cement concrete may be used The properties of concrete and mix proportions shall be as given in IS 456‐1978 It shall be permissible to proportionate the concrete as follows Prepare a wooden measuring box of 35 lit capacity (ie equal to 1 bag of 50 kg of cement) with inside dimensions of 30 cm x 30cm x 39cm alternatively a cylinder of 34 cm diameter and 39 cm height shall be made ready for the proportioning
bull The mix quantities according to the measuring box shall be as follows M20 (1153) M15 (124 mix) M10 (136 mix) bull Cement 10 1 Bag 1 Bag bull Sand 15 2 Boxes 3 Boxes bull Metal 30 4 Boxes 6 Boxes
The required quantity of water shall be used for concrete mix The water should be free from oilacid and any other impurities Saline water or sea water should not be used for the concrete work The concrete shall be mixed in the mechanical mixer only However in case of difficult terrain hand mixing may be permitted at the discretion of Engineer In charge Mixing shall be continued until there is uniform distribution of material and the mix is uniform in color and consistency but in no case the mixing be done for less than two minutes Normally mixing shall be done close to the foundation but in case it is not possible the concrete may be mixed at the nearest convenient place The concrete shall be transported from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any ingredient or setting The concrete shall be placed and compacted before setting commences Mechanicalpneumatic vibrator shall be used for obtaining homogenous concrete work and for better finish as well as avoiding honey combing 312 Specification For From Box 3121 The general requirements of form box are as under
bull The form work shall conform to the shape lines and dimensions as shown on the approval foundation design drawings and be as constructed as to the rigid during the lacing and compacting of concrete and shall be sufficiently tight to prevent loss of liquid from concrete
bull It shall be of right design easily removable without distortions and shall be of steel or suitable materials
bull The inner surface coming in contact with concrete shall be smooth and free from projections bull Window on one face shall be provided for pyramid forms to facilitate concreting in the lower
parts which shall be fixed after concrete in the bottom part is placed bull The form work for slabs and pyramids shall be made symmetrical about the base of the
chimney to ensure interchangeable faces
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 18
3122 Clearing and Treatment of Forms bull All rubbish particularly chippings sawdust and traces of residual concrete if anyshall be
removed from the interior of the forms before the concrete is placed bull The surface in contact with the concrete shall be wetted and spread with the fine sand or
treated with an approved compositions such as black or waste oil etc before use every time bull The concrete shall be poured in 150mm layers and consolidated well so that the cement cream
works up to the top and no honey‐combing is left in the concrete bull The mechanical vibrator shall be employed for compaction of the concrete bull However in case of difficult terrain manual compaction may be permitted at the discretion of
site Engineer bull After concreting the chimney portion to the required height the top surface should be finished
smooth with a slight slope towards the outer edge to drain off any rain water falling on the coping
3123 Wet Location bull In wet locations the site must be kept completely dewatered both during the placing of the
concrete and for 24 hours thereafter bull There should be no disturbance to concrete by water during this period
3124 Removal of From Box After the form work has been removed if the concrete surface is found to be defective the damage shall be repaired with rich cement and sand mortar to the satisfaction of the Ownerrsquos representatives before the foundation pits are backfilled 313 Back Filling and Removal of Stub Template 3131 Process of bake filling The back filling work is very important for the stability of the foundation Following is recommended
bull Backfilling shall normally be done with the excavated soil if the excavated material includes large bouldersstones the boulders shall be broken to a maximum size of 80mm
bull At such locations where borrowed earth is required for backfilling this shall be done by the Contractor as per the rates terms and conditions laid down in the contract
bull If the foundation cast is rocky type backfilling with the borrowed earth may not serve the purpose
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 19
bull In such a case backfilling with chipped stones mixed with the cement slurry would be a better option
bull However this would be done as per the instructions of the engineers in change 3132 Material for bake filling The following is required to be noted for the back filling material
bull The backfilling materials should be clean and free from organic or other foreign materials bull The earth shall be deposited in maximum 200mm layers leveled and wetted and tampered
properly before another layer is deposited bull Care shall be taken that the backfilling is started from the foundation ends of the pits towards
the outer ends bull After the pits have been backfilled to full depth the stub template may be removed bull In case of urgency the template can be removed even after 50 of backfilling of the soil bull The backfilling and grading shall be carried to an elevation of about 75mm above the finished
ground level to drain out water bull After backfilling 50mm high earthen embankment (bandh) will be made along the sides of
excavation pits and sufficient water will be poured in the backfilled earth for at least 24 hours 3133 Curing The strength of concrete work depends upon the curing provided to it Following requires to be noted
bull The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period 10 days after lying
bull The curing will be done from the top of the pit within the embankment area bull No saltish or brackish water shall be utilized for curing
3134 Earthing Earthing of tower is very important for the performance of insulators and conductor of the transmission line Each tower shall be earthed after the foundation has been cast For this purpose earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level In normal circumstances the earth strip shall be provided on No1 stub leg as given in the structural drawings Normally the tower leg whish has the step bolt is provided with the earthing strip Following may be noted
bull The footing resistance of all towers shall be measured by the Contractor in dry weather after the erection of superstructure but before the stringing of earth wire
bull In no case the tower footing resistance shall exceed 10 ohms bull In case the resistance exceeds the specified values multiple pipe earthing or counterpoise
earthing shall be adopted in accordance with the following procedure but without interfering with the foundation concrete even though the earth stripcounterpoise lead remains exposed at the tower end
bull The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top
Pipe type earthing and counterpoise type earthing wherever required shall be done in accordance with the stipulations made in IS3043‐1966 and IS5613 (Part IISection 2) 1976
bull Pipe type earthing The installation of the pipe type earthing shall be in accordance with IS 5613‐ 1985 (part IIsection 2) A typical example of pipe type of earthing is given
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 20
bull Counter poise type earthing
Counterpoise type earthing consists of four lengths of galvanized steel stranded wires each fitted with a plug for connection to the tower leg at one end The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level The length of each wire is normally limited to 15 m but may be increased if the resistance requirements are not met (ie 10 ohms or less) Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose Such type of earthing is provided for hilly terrain locations where earth pit excavation to a depth of about 25 to 3 m is not feasible and the resistivity of the earth is very high
40 Erection of Super Structure and Fixing Of Tower Accessories 41 The towers shall be erected on the foundations only after 10 days of pouring of concrete or till such time that the concrete has acquired sufficient strength The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection For the convenience of assembling the
COMPAQ
PIPETYPE TOWER EARTHING FOR LOW RESISTIVTY ZONEdwg
COMPAQ
COUNTER POISE TYPE TOWER ESRTHINGdwg
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 21
tower parts during erection operations each member is marked in the factory to correspond with a number shown in the erection drawing Any damage to the steel and injuring of galvanizing shall be avoided while the stringing work is in progress No member shall be subjected to any undue over stress during erection 42 Method of Erection There are four main methods of erection of steel transmission towers which are described below
43 Build up Method This method is most commonly used in this country for the erection of 66KV 132KV 220KV and 400KV transmission line towers due to the following advantages
bull Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation loading and unloading
bull It does not require any heavy machinery such as cranes etc bull Tower erection activity can be done in any kind of terrain and mostly throughout the year (save
difficult time of heavy rain) bull Availability of workmen at reasonable rates bull In this method the tower is erected member by member bull The tower members are kept on ground serially according to erection sequence bull The erection progresses from the bottom upwards bull The four main corner leg members of the first section of the tower are first erected and guyed
off bull Sometimes more than one continuous leg sections of each corner leg are bolted together at the
ground and erected bull The cross braces of the first section which are already assembled on the ground are raised one
by one as a unit and bolted to the already erected corner leg angles bull First section of the tower thus built and horizontal struts (belt members) if any are bolted in
position bull For assembling the second section of the tower two gin poles are placed one each on the top
of diagonally opposite corner legs bull These two poles are used for raising parts of second section bull The leg members and bracings of this section are then hoisted and assembled bull The gin poles are then shifted to the corner leg members on the top of second section to raise
the parts of third section of the tower in position for assembly bull Gin poles are thus moved up as the tower grows This process is continued till the complete
tower is erected bull Cross‐arm members are assembled on the ground and raised up and fixed to the main body of
the Cross‐arm members
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 22
For heavier towers a small boom is rigged on one gin pole is used instead of two gin poles In order to maintain speed and efficiency a small assembly party goes ahead of the main erection gang and its purpose is to sort out the tower members keeping the members in correct position on the ground and assembling the panels on the ground which can be erected as a complete unit
COMPAQ
COMPAQ
tower under bottom cross-arm erectiondwg
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 23
44 Section Method bull In the section method major sections of the tower are assembled on the ground and the same
are erected as units bull Either a mobile crane or a gin pole is used bull The gin pole used is approximately 10 m long and is held in place by means of guys by the side
of the tower to be erected bull The two opposite sides of the section of the tower are assembled on the ground bull Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into
position on bolts to stubs or anchor bolts bull One side is held in place with props while the other side is being erected bull The two opposite sides are then laced together with cross members and diagonals and the
assembled section is lined up made square to the line bull After completing the first section gin pole is set on the top of the first section bull The gin rests on a strut of the tower immediately below the leg joint bull The gin pole then has to be properly guyed into position bull The first face of the second section is raised bull To raise the second face of this section it is necessary to slide the foot of the gin on the strut of
the opposite face of the tower bull After the two opposite faces are raised the lacing on the other two sides is bolted up bull The last lift raises the top of the towers
COMPAQ
COMPAQ
tower cross-arm under erectiondwg
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 24
bull After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole
bull Sometimes whole one face of the tower is assembled on the ground hoisted and supported in position
bull The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted
45 Ground Assembly Method bull The complete tower is assembled in a horizontal position on an even ground bull The tower is assembled along the direction of the line to allow the cross arms to be fitted bull On slopping ground however elaborate packing of the low side is essential before assembly
commences After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location and set on its foundation
bull For this method of erection a level piece of ground close to footing is chosen from the tower assembly
bull This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on sloping ground may not be possible and it may be difficult to get crane into position to raise the complete tower
bull In India this method is not popular because of prohibitive cost of mobile crane and non availability of good approach roads to tower locations
46 Tightening Of Nuts amp Punching of Threads and Tack Welding of Nuts 461 Following are the requirements for tightening of nuts and bolts
bull All nuts shall be tightened properly using correct sized spanners bull Before tightening it is ensured that filler washers and plates are placed in relevant gaps
between members bolts of proper size and length are inserted and one spring washer is inserted under each nut
bull In case of step bolts spring washer shall be placed under the outer nut bull The tightening shall be carried on progressively from the top downwards care being taken that
all bolts at every level are tightened simultaneously bull It may be better to employ four personnel (fitters) each covering one leg and the face to his
right bull The threads of bolts shall be projected outside the nuts by one to two threads and shall be
punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not loosened in course of time due to the effect of the vibration
bull If during tightening process a nut is found to be slipping or running over the bolt threads the bolt together with the nut shall be changed outright
bull To prevent the pilferage of the tower members it is a common practice these days to tack weld the nut with the bolt in threaded portion
bull The welding is generally done for lowermost two sections of the tower bull The galvanization of nuts and bolts is lost due to welding bull This has to be made good by the application of zinc rich paint
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 25
462 Painting of Joints For galvanized tower in coastal or highly polluted areas the joints shall be painted with zinc rich paint on all contact surfaces during the course of erection 463 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height 47 Tower Testing and Protomodel 471 Introduction Transmission line towers are highly indeterminate structures In the analysis of design of these structures and their detailing a number of theoretical assumptions are made The structures are mass produced and the quality of materials fabrication and the assembly require checking It is desirable that the Designers and Users both are convinced that the tower can stand and most critical loads for which it is designed and are therefore subjected to full scale prototype test For a Prototype test the material used shall be made to the same standards as those that will apply to all towers during mass production 472 Testing Requirements This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behavior of the tower on application of the external design loads 473 Description of a Tower Testing Station A tower Testing Station shall consist of (i) A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and noofr circuits which has to be subjected to testing at the Testing Station (ii) Permanent Anchors of adequate capacity to take the Transverse Longitudinal and Vertical Pulls applied to the tower of maximum expected with height and strength proposed to be tested on a test bed Longitudinal Mast(P) is a structure of adequate dimension and height constructed at a sufficient distance from the tower bed and equipped with all Riging arrangements for applying longitudinal loads The Transverse loads are applied through pulleys positioned on the Transverse Mast (B) Vertical loads are applied by means of dead weight or through anchors on the test bead (iii) The arrangements for applying the combination of given loads at a specified rate of increase if required with the help of a Multi Sheave Pulley to take mechanical advantage and reduce load on the winch (iv) Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure as far as possible simultaneously Instruments used for recording the load applied are either Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers The dials of the respective DynamometersTransducers indicate the load in the particular wire Transverse amp longitudinal deflection readings are taken by Theodolities on scales fitted at appropriate positions on the tower (v) Remote control of loading mechanisms (vi) Remote and precise reading of measuring instruments like Mechanical Spring Gauges or ElectricalElectronic TransducersDynamometers
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 26
(vii) Arrangement for calibration of the measuring instruments From Control Room the winches and the dynamometers are operated controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower All the electrically operated machines and instruments shall be connected to and controlled from the Control Room 474 Calibration In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the tests the calibration of all instruments before the test is conducted Calibration of the load cells is done with the use of UTM the UTM shall be periodically (once in every six months) calibrated by an external third party 475 Assembly of Prototype Tower The prototype tower fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a fixed base Fitment of any member shall be easy natural and shall not be a forced one The Bolts should be tightened simultaneously on all four faces 476 Rigging Arrangements And Location of The Load cells To enable application of the external loads in the most representative manner and to simulate tower design conditions the tower structure is rigged suitably impact of any variance in inclination of rigging wires with respect to the directions accounted for in designs is considered while preparing Rigging Chart Loads are applied as per these approved rigging charts The load cells shall be attached to the tower through the rigging wires positioned as close as possible to the test tower so that frictional losses do not cause impact on the load cells 477 Test Procedure The Prototype Tower is erected on the test bed and all the rigging arrangements are completed The Tower is examined carefully to see that all the bolts and nuts are tightened properly The tower is made truly plumb and square All its members are checked for freedom from any visible defect Two graduated metallic scales are fixed at Peak and Top Cross arm level on the transverse face Readings on these scales with reference to the plumb line are taken by Theodolite 478 Testing of Prototype Tower 4781 Bolt‐Slip Test In order to eliminate as far as possible the play between the bolts and the holes throughout the structure Bolt take‐up test is done in the beginning Under this test all the transverse and vertical loads are increased simultaneously as far as possible to 50 of the ultimate normal condition (Reliability Condition) loads The loads on the tower are held for 1 minute Transverse deflection readings are taken for NO LOAD and LOADED conditions The loads on the tower are then reduced to zero or to as low a value as possible The deflection reading is once again taken for this Zero loading The differences between the two zero readings are the permanent deflections on tower For subsequent test purposes the readings with zero loads taken after the Bolt Slip Test taken are considered as the initial readings 4782 Sequence of Test Loading Cases Sequence of test loading cases shall be pre‐determined The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 27
4783 Details of Tests Test 1 (Broken wire Condition) Security and Safety Conditions as well as Anti‐cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100 Longitudinal loads are then increased in steps of 50‐75‐90‐95 of the ultimate loads At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load At each step the loads are maintained for one minute and the deflections are noted All loads are then increased to 100 At this final 100 loading stage towe3r is observed for 2 minutes and deflections are noted The tower is required to withstand these loads without showing any failure After every test the loads are brought down and deflection readings are taken for no load condition Test 2 (Normal Condition) Reliability Condition These loads are applied as far as possible simultaneously at all points in steps of 50‐75‐90 amp 95 The waiting period of one minute shall be maintained at each step The waiting period at the final 100 loading stage shall be 2 minutes Throughout the process of loading under all tests the tower shall be closely observed for any visual sign of deformation Whenever such deformation is observed the loads shall be brought down and remedial measures shall be taken It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period Test 3 Destruction Test If no Destruction Test is required by the Purchaser the loads on tower after 100 under Test‐2 above shall be gradually brought down to zero If desired by the Purchaser in continuation to test 2 after the final waiting period the transverse loads only are increased in steps of 5 till the failure occurs The Destruction test however ca be discontinued beyond a certain limit on mutual agreement between the Purchaser Design amp Testing Station Authority The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room 478 Special Requirements
bull The test tower shall be black or galvanized tower as desired by Purchaser
bull The tower which has been tested shall not be part of supply and is not to be used online
bull Test tower shall be provided with unbraced portion of stub equivalent to distance of chimney top to the point of connection of bracing with leg
bull During the process of tower test when a number of tests have been completed satisfactorily and a failure occurs as a subsequent test the design will be reviewed and tower will be reinforced if required The reinforced tower will be put to test again and subjected to balance tests unless the failure is of major nature which will require all the tests to be repeated or as mutually agreed between the Purchaser and the Supplier
bull Application of Loads on Test‐Tower As considered in design
Transverse longitudinal and vertical loads At peak and respective cross‐arm points (i) Wind load from top at peak and respective cross‐arm points upto bottom cross‐arm will be simulated suitably at ground‐wire Top Cross‐arm Middle cross‐arm and Bottom cross‐arm levels
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 28
(ii) Wind loads on tower below bottom cross‐arm will be simulated to act at bottom cross‐arm point and test will be carried out accordingly (iii) For tower with extension wind load on extension will be simulated on Top of Extension
479 Acceptance of Test Results Test is considered as passed if tower is able to withstand the specified ultimate loads (100 step) with no visible sign of deformation for the specified waiting period A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test‐authority in quadruplicate 4710 Presentation of Test Results
50 Conductor amp Conductor Accessories 51 Conductors The different types of conductors are used on the transmission line depending upon the voltage class and amount of current to be handled In India it is a standard practice to use following conductors for different voltages 1 66kV ‐ACSR ldquoDogrdquo conductor 2 66 132kV ‐ACSR ldquoPantherrdquo conductor 3 220kV ‐ACSR ldquoZebrardquo Conductor 4 400kV ‐ACSR Twin Bundle ldquoMoose ldquoConductor
TABLE ‐1
Sr No
Name of
Conductor
Normal operating voltage
kV
Size amp stranding
Alu Steel Nomm Nomm
Current carrying
capacity at 75ordmC (Amp)
Over all
dia cm
UTS Kg
Unit
weight KgMtr
1 ACSR Dog
3366 6472 7157 300 12
3299 0394
2 ACSR Panther
66132 3030 730 480 210 9177 0976
3 ACSR Zebra
220 54318 7318 735 286 13316 162
4 ACSR Moose
220400 54353 7353 800 318 16250 202
For special industrial connections at EHV the conductor size shall be worked out on the basis of maximum system current The insulation is provided in accordance with the voltage 52 Insulators 521 The standard type of conductor if used has also an advantage that the current carrying capacity voltage loading limit and impedances are also standardized and well defined Thus there is an easy access for a system analyzing engineer for evaluation and assessment of power flow and optimum line loading Thus the current loading limit and power transfer capability of various transmission lines are given in Table‐2 They are based on the allowable voltage regulation on EHVUHV lines
SrNo Line Voltage Power Transfer capability per 3‐phase Circuit(MW)
50kM 100kM 200kM 300kM
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 29
1 66kV 22 11 55 36
2 132kV 120 60 30 20
3 220kV 400 200 100 67
4 400kV 1500 750 375 250
522 In case of transmission line having a concentrated load and low voltage it may become mandatory to use higher size of conductor eg system having 33kv line voltage with two loads of 10 and 30MW at end of 4 to 5kM long feeder may require ldquoZebrardquo conductor to be strung on it Since with reduction in voltage the current to be carried becomes very high and use of lower size of conductor may be hazardous Similarly a lightly loaded 132kV lines can also be strung with ACSR ldquoDogrdquo conductor The thermal loading limits of the conductor are increasing day by day Of‐late it has been customary to consider 75ordmC as a maximum surface temperature of the conductor Operating lines at high thermal limits is not advisable due to two reasons i) Line losses increase with increase in temperature ii) Sag may increase bringing down the statutory clearance below the conductor to non acceptable level With this in view the conductors used in the substation buses are one size up in diameter or in bundle configuration Thus the 220kV side bus of 400kV substations may have quadruple ldquoMooserdquo conductor and 66kV bus of 220kV substation may have a Twin ldquoZebrardquo or Twin ldquoMooserdquo conductor (Bus) 53 Choice of Insulators The glazed disc type porcelain insulators have been a standard material in use for last 50 years in this country The insulator string consist of No of disc unit in optimum width at about 135kV per disc up to
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 30
a voltage of 220kV For 400kV class of line the insulator size and creep age distances are higher and thus No of insulators to be used are 23 for suspension and 24 for tension tower The important parameters for disc insulator string used in various voltage of transmission line are given in Table‐3
Table‐3
Sr No
Line
Voltage
Size of each
insulator disc(D x H)
mm x mm
Electro‐mech
StrengthKg
Noof insulators per string
Single Double
No No
Weight of Insulator
String Single
Double Kg Kg
Length of insulator
string Single
Double mm mm
1 66kV Suspension Tension
255 x 146 255 x 146
7000 8180
5 6
10 12
75 85
150 170
1000 1140
1300 1280
2 132kV Suspension Tension
255 x 146 255 x 146
8180
11500
9
10
18 20
120 130
240 260
1600 1790
1716 2190
3 220kV Suspension Tension
255 x 146 255 x 146
8180 11500
14 15
28 30
130 140
260 280
2340 2850
2640 3200
4 400kV Suspension Tension
255 x 146 255 x 146
11500 16500
23 24
46 48
275 640
550
1280
4200 5900
4400 6200
531 Other insulator types in vogue these days are a solid core insulator stack and high density polymer insulator Even though the polymer long rod insulators are simpler and low weight they are yet to be popular in this country because of very high cost 532 The design of insulators does not only depend upon the creep age `distances but they have many intricacies such as the type of material used in the insulators capacitance grading thermal capability back flash over etc 533 The insulators used on the line are also governed by the basic insulation level selected in power system 534 The choice of disc insulators to be used depend upon the terrain amp the pollution level through which the transmission line has to pass and thus fog type and antifog type disc insulator are in use for different applications The antifog type insulators are in use for different applications The anti‐fog type insulators are found most suitable in the polluted atmosphere 54 Conductor Accessories 541 Mid span Joint ndash It is used to provide joint in the conductor For AC Conductor the joint comprises one small steel tube and the other bigger Aluminum tube The steel tube is compressed (crimped) against the two ends of Steel which are exposed by peeling of the Aluminum Strands for half the length of steel tube strands of ACSR amp the Aluminum strands Hydraulic equipments are used for crimping For AAAC or AAC conductor only Aluminum tube is used which is also crimped after steel tube is crimped after sliding over the crimped steel tube
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 31
542 Repair Sleeve ndash It is used when one or two strands of the outer Aluminum strands are broken The sleeve is manufactured in two parts longitudinally and circumferentially major part is 70 on diameter and minor part is 30 on diameter The length of both the parts is the same After sliding both the parts on the conductor the sleeve is crimped on the affected part
543 Pre‐formed Armor rods ndash This is a set of twelve helical right hand ball ended Aluminum rods of appropriate length The set is wound on the conductor at suspension tower location and then the entire assembly along with the conductor is clamped in the suspension clamp The PA rods prevents damage and reduces fatigue on the conductor due to the relative movement of the clamp and the conductor and also helps in reducing the effect of conductor vibration on clamp amp the tower cross‐arm
544 Vibration Dampers ndashThey are used to damp the Aeolian vibrations on the conductor The dampers are clamped to the conductor near the cross arm point on both the sides at a distance of 3 to 5Mtr The vibration damper comprises a clamp a messenger cable and dead weight The dampers can be solenoid type or 4R type
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 32
545 Spacer cum Dampers‐ They is used for bundle conductor spacing and for damping the vibrations They comprise two arms with clamping device and a spacing yoke having a spring action They are made of Aluminum 546 Cushioned (Armour grip) spacers‐ They are used as spacers for bundle conductor with amour grip They comprise an aluminum rod two neoprene rubber jaws and two sets of armour rods (each having six rods) Rigid spacers are used for twin bundle conductor jumpers 547 Earthwire ndash The earth wire is used for protecting the conductor in the mid span It is provided at such a height which affords an angle of shield not more than 30ordm with Top conductor The common size of earth wire used is 7315 and 7366 In case of 400kV and above two earth wires are used for better protection Earth wire Accessories includes the following 5471 Suspension Clamp ‐ This is used for suspending the earth wire through the earth wire peak of the transmission tower The earth wire passes through the suspension clamp
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 33
5472 Tension Clamp ‐ This is used on tension locations of tower and provided in tension position on both the sides of the tension tower
5473 Copper Earth bond‐ This is used for providing direct passage to the lightning surge to the tower The copper bond is made out of stranded copper mesh with two lugs on the ends and is about 500mm long One end of this is connected to the suspensiontension clamp of earth wire and the other end is connected to the tower body
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 34
5474 Cross bye clips (sister wire clamps) ndash This is used for providing better continuity to the earth wire They are nothing but a sort of parallel groove clamp They are provided in set of three from either side of the tower
5475 Mid Span Joint ‐ This is used to connect the cut ends of the earth wire This is nothing but a steel tube which is crimped on the ends of the earth wire
548 The Insulators are connected in series or in series ndashparallel to form a single or double string on the tower Suitable hardware is required for securing the insulators to the tower The insulator hardware commonly used is as follows‐ 5481 Single Suspension hardware ndash This is used on suspension locations of the tower line falling in the rural areas and also falling in the agricultural field The hardware has a hook on the tower side and socket on the conductor side
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 35
5482 Double Suspension hardwaremdashthis is used on suspension tower locations which require a road crossing or a railway crossing amp river crossing They have anchor and a yoke on the tower side and yoke amp sockets on line side They also have a Suspension clamp on the line side
5483 Single Tension hardwaremdash This is used on tension tower locations This hardware has a shackle on the line side and a dead end clamp on the line side
5484 Double Tension hardwaremdash This is used on tension tower location having a major road crossing river crossing power line crossing railway crossing etc They have D‐shackle yoke on tower side and yoke dead end clamps on the line side
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 36
55 Relation of Conductor With Transmission Line Components 551 The Transmission line components described above has relation with the conductor Some salient points are described below‐ The earth wire provided on the tower provides a cover to the conductor against lightning surges if the conductor is placed within an umbrella of 30ordm degrees If earth wire is not provided or is missing the conductor will be loaded by lightning and stray discharges The conductor will carry this along the line and insulators may get damaged The earth wire accessories help in supporting the function of earth wire The transmission tower provides full support to the conductor with two extremities ndash a) To allow sufficient ground clearance and object clearance to the conductor under maximum temperature amp still air b) Absorb the maximum tension of the conductor under 0ordmC temperature with certain percentage of wind pressure Any deficiency in the tower design will lead to a catastrophe 552 The insulators keep the conductor in position on suspension and tension locations amp also insulate the conductor from the tower body Any damage to insulator will cause a short circuit on the conductor and may also lead to the break down 553 The hardware part of the insulator string is very important for the performance of the conductor Any loose end will result into damage to the conductor The hardware permits the conductor to swing to some extent and also restrains the conductor from over swing 554 The earthing system provides a safe passage to the fault current amp lightning switching surges If earthing system is poor the life of conductor and insulator will be reduced 555 The long span of River amp Creek Crossing imposes differential stresses due to variation in wind pressure and temperature along the long span The length of the catenary is very long amp therefore the conductor swing is also very big The variation in wind velocity over tall tower also steps up the vibration level
60 Stringing of Conductor and Ground Wire
61 Stringing is the last major item of construction activity The stringing activities are most important and time consuming activities in transmission line construction This requires much skill and technical know‐how The stinging crew shall include skilled laborers experienced fitters and supervisor The stinging tools and tackles should be of good quality and in good working condition
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 37
62 The stringing activities are mainly consisting of the following bull Hoisting of insulators bull Paying of conductorground wire bull Rough sagging of conductor bull Final sagging of conductorground wire bull Clippingclamping of conductor and jumpering
63 Hoisting of Insulators Following may be noted for hoisting of insulators
bull The insulators used on transmission lines are 11KV antifog type Disc insulators having capacity as 70KN 90KN 120KN and 160KN
bull The suspension insulator strings shall be used on all suspension locations (tangent towers) and tension insulator strings on all tension locations (angle towers having153060deg Deviation and Dead end towers)
bull The insulator strings shall be assembled on ground bull All the insulators shall be cleaned and examined for hair cracks or any damage bull The strings are then hoisted and fixed to the tower cross‐arm along with hardware and Arial
rollers bull The security clips (R pinW pin) should be properly placed before hoisting
COMPAQ
PROCEDURE FOR STRINGING OF CONDUCTOR WIRESdwg
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 38
64 Paying out of ConductorGround wire Following may be noted for paying of conductor
bull Before commencing of string works copies of sag tension charts (supplied by the design department) showing initial and final sag should be made available at site to EIC
bull Normally ground wire drums are mounted on turntable near tension location bull The ground wire is pulled manually or by tractor along the line The ground wire running blocks
are hoisted on the towers prior to taking up this operation bull The ground wire drums should be opened and laid carefully in such a way to avoid
cracksdamages bull It should be ensured that no joint in ground wire is within 30m from the suspensiontension
clamp bull Sufficient number of aluminum snatch blocks shall be used for paying out of conductor bull Precautions should be taken to avoid conductor rubbing on the ground by providing adequate
number of ground rollers bull Additional rollers shall be provided for crossing thorny hedges fencing and other obstructions
which are likely to cause damage to the conductor bull No joints of conductor shall be allowed within 30m from suspensiontension hardware bull In case of railwayroad crossing spans no joints shall be permitted Further not more then one
joint in a span of each conductor shall be permitted bull Prior to taking up of conductor paying activity the areal rollers are fitted to the towers along
with suspension strings bull The conductor drums should be handled carefully at site to avoid any damage to the outer
aluminum layer bull The mid span joints and tension hardware are compressed by using hydraulic compression
machine bull All the compression joints shall be carefully made and a record of initial and final lengths of the
joints signed by the contractorrsquos and purchaserrsquos representative should be maintained 65 Rough Sagging of Conductor
bull On completion of conductor paying work between two tension locations (ie is line section) the conductors of all the phases shall be anchored near the tension location
bull During the rough sagging the conductor will be lifted above the ground by about 3 meters bull Thus the tension on the wire will minimum
66 Final Sagging of ConductorGround wire Following may be noted for final sagging of conductor ground wire
bull The conductor and ground wire shall be made to sag correctly as per the approved stringing charts
bull All conductors shall be stressed to their maximum working tension at the time of stringing according to the sag tension charts
bull Dynamometers shall be used in tensioning of conductors check for sag should also be made at intervals corresponding to the ambient temperature shown by the thermometer placed at site
bull Extra sag of 150mm should be allowed at all important tension locations of railway crossing major road crossing river crossing spans
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 39
bull It should be ensured that the conductor ground wire after being pulled shall not be kept on stringing sheaves for more than 72 hours before being pulled to the specified sag
bull During the time when conductorground wire is on the stringing sheave (before final sagging) it shall be ensured no damage of conductorground wire occurs due to wind vibrations vehicles or any other reasons
bull The conductor shall be pulled up to desired sag (final sag) and left in aerial stringing sheaves for at least one hour After which the sag shall be rechecked and adjusted if required before clipping work is taken on hand
bull During final sagging of conductor the sag at intermediate spans should be verified with the help of sag board provided at suitable distances (as per the approved stringing chart and the corresponding site temperature) on the tower body of intermediate locations
bull The stringing of bundle conductor (two or more conductor) shall be carried out by using tension stringing equipment
bull Using this method the conductors are kept under tension during the stringing process to keep conductor clear of the ground and obstacles which may cause conductor surface damage as well as clear of the energized circuits
bull This method is applicable where it is desired to keep the conductor off the ground to minimize surface damaged or in areas where frequent crossings are encountered
bull The equipments involved in this method are reel stands tensioner pullers reel winder pilot line winder splicing cart and pulling vehicle
bull One more important reason to use the tension stringing equipment for stringing of bundle conductor is to release payout rough sag and final tensioning of all the sub‐conductors of the bundle under equal physical tension
bull This will ensures equal sags of each sub‐conductor in a span and sub‐span 67 ClippingClamping of Conductor and Jumpering The clippingclamping work includes fixing of suspension hard wares providing of preformed armour rods removal of aerial sheaves etc Following required for clipping clamping
bull Conductor shall be clamped within 24 hours of final sagging bull The sag before clamping should be checked in the first and last span of the section having
eight spans bull The check should be provided at intermediate span also if the section is having more than eight
spans bull At all the suspension locations the preformed armour rods shall be wrapped keeping the
centre of the preformed armour rods at the centre point of the stringing sheaves bull Care should be taken to see that all the strands of the rods are fixed on the surface of the
conductor without any void bull The suspension clamps of the suspension hardware should be fixed (bolted) at the centre of the
preformed armour rods bull The vibration dampers should be fitted on tension locations at an appropriate distance from
the tension hardware (specified by the design department) during the rough final sagging of conductors
bull The vibration dampers on suspension locations shall be fitted at an appropriate distance on either side of the suspension hardware as specified
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 40
bull The jumpering work of conductor includes cutting of proper length of jumper providing of jumper cones on both the ends of jumper fixing of the jumper to the tension hardware on either side of the tension location etc Care should be taken to compress the jumper cones with hydraulic compressor machine so as to have firm grip with the conductor
bull The tightening of boltsnuts should be proper over tightening should be avoided bull The clearance with the tower body after providing jumpers shall be checked as per the
approved tower drawing bull The ground wire jumpers are also prepared using appropriate length of ground wire having
compressed jumper cones on either side bull The prepared jumpers shall be then fitted to the tension clamps on either side of the tension
locations bull An additional ground wire piece called sister wire is fitted on the newly strung ground wire at
the top of all the locations using 2 to 3 numbers of cross by clips also known as sister wire clamps on either side of the locations
bull The bolts and nuts of cross by clips should be properly tightened bull The vibration dampers for ground wires shall be provided at appropriate distance on either side
of the location as specified bull The earth wire stringing is normally done before the stringing of conductor bull The rough sagging and final sagging is done exactly as per the procedure described for
conductor bull The approved stringing charts are used for stringing of earth wire bull After final tensioning of the earth wire the suspension clamps are provided on the suspension
locations and compression type dead end clamps are provided on the tension locations bull Jumpering work is done on the earth wire tension tower bull Sister wires and clamps are provided on each tower making an additional loop on the top of the
earth wire point which also ensures better conductivity amp continuity bull The earth wire suspension and tension clamps are connected to the main tower body using
braided copper earth band bull This earth bond gives direct path to the lightning discharges traveling on the earth wire to the
mother earth through towers and safe guards the conductors bull Vibration dampers are also provided on the earth wire to damp the Aeolian vibrations The
clamps are required to be properly tightened to ensure proper connectivity and trouble free service
68 Fixing of Tower Accessories After the stringing work is done it is necessary to fix the tower accessories such as phase plate Number plate Danger plate Circuit identification plate Anti climbing devices etc as per their respective position shown on the structural drawings 69 Protection of Towers
bull In the hilly terrain the foundations of the tower are susceptible to the damage due to the erosion of soil covering it
bull This happens because of gushing water from upstream Sometimes the tower is spotted on the ravines or river banks and one or more of the four tower legs are subjected to soil erosion
bull In both the above cases it is usual to provide retaining wall and or revetment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 41
bull Whenever the Transmission line is passing through a corridor having major road on both the sides or the tower line is passing very near to the major road it is necessary to provide a steel barrier around the tower up to height of 3 meters
bull This barrier has to be sufficiently strong and made out of girders and channels bull The barriers have to be well founded to take the impact of the dashing vehicles
70 Details of Manpower Tools Tackles Equipment Vehicles and Infrastructure Required For the Construction of The EHV Transmission Line 71 The details of man power tool tackles equipments and vehicles required for the construction of EHV line of various voltage classes such as 66 KV 132 KV 220 KV and 400 KV etc are given here after The erection activities are spread over a long period and are mostly carried out in the rural areas and therefore appropriate infrastructure is required The activities are labor oriented and besides there are restrictions on the use of automatic machineries due to the constraint of cost and the constraint of movements in the rural and in‐accessible tower and line locations The transmission line construction activity generally includes‐
bull Survey and alignment bull Foundation work bull Erection of super structure bull Stringing of shield wire and conductor bull Testing and Commissioning
Each of the above activity need different types of tools tackles man power etc The details given here under give a broad view of the tools tackles equipments man power and other infra structure required in the construction of EHV transmission lines 72 Infrastructure for Survey
bull This is the first and foremost activity in the transmission construction bull Expert surveyor assisted by helpers and suitable vehicles to carry instruments is the basic need bull This survey work is different from the survey work required to be done for civil establishments
COMPAQ
COMPAQ
RIVETMENT FOR THE TOWERdwg
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 42
bull The surveyor must have the knowledge of preparing profiles and also various methods to carry out the correct survey
bull The surveyor should also have in‐depth knowledge of tower spotting bull The infra structure required for carrying out survey work is listed below bull Average output per month per gang consisting of about 10 crew members will be
(i) Alignment survey 15 km (ii) Detailed Survey 20 km (iii) Check Survey 20 km
bull Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work and terrain
bull The output in hilly terrain may be substantially low bull Tools required for Survey Gang
Theodolite(or Total Station) with stand 1 NODumpy level with stand 1 NORanging rod 5 NOLeveling Staff 2 NOEngineers chain ‐30 m 1 NOEngineers chain ‐20 m 1 NOSteel Tape ‐30 m 1 NOSteel Tape ‐20 m 1 NOSurvey umbrella 1 NOChain pins 30 NO
Spades knives and exes for clearing the bushes and trees As per requirement
Tents buckets water drums camping cots tables chairs petromax etc As per requirement
Transport required for Survey Gang Jeep with trailers 1 NO 73 Foundation activity
bull This activity has to be carried out from location to location spread over a distance which is sometimes as large as 400 meters Excavation has to be carried out in various types of soils and rocks
bull The excavation plan will change accordingly Sometimes in hilly locations we may have to blast the rock In case sub soil water is encountered during excavations dewatering has to be resorted to In case soil collapse shoring and shuttering are required The foundation depth may vary from 1m to 5m depending upon the soilrock and decision regarding the type of foundation has to be adopted The infra structure required for this activity is as below
Average output per gang consisting of about 85 people per month will be
Excavation
60 msup3 Soft rock 400 ‐500 msup3 Normal soil
150 msup3 soft rock +180 msup3 normal
soil Output of hard rock will depend on situation
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 43
Stub‐setting amp Concreting 60 ndash 70 msup3 Tools and Plants required for Excavation Stub‐setting and Concreting Gang
Stub‐setting Templates As per
requirement Stub‐setting Jacks ‐do‐ Form boxesChimneys ‐do‐ Mixture Machine ‐Diesel engine driven 1 NO Mixture Machine ‐ Hand driven 2 NO Needle vibrator 1 NO Dewatering pump 2 NO Air compressor for drilling holes in rock 1 NO
High carbon drilling rods for drilling holes in rock As per
requirement Exploder 1 NO Water tanker trailor 1 NO Theodolite with stand 1 NO Ranging rod 3 NO Dumpy level with stand (or Total Station with Prism) 1 NO Leveling staff 1 NO Survey umbrella 1 NO Concrete cube mould (for testing the concrete) 6 NO
Wooden shuttering amp poles As per
requirement Mixing Sheets 12 NO Measuring Box 6 NO Metal screen (for course aggregate) ‐ 40 mm mesh 1 NO Metal screen (for course aggregate) ‐ 20 mm mesh 1 NO Metal screen (for course aggregate) ‐ 125 mm mesh 1 NO Sand screen ‐ 475 mm mesh 1 NO Empty barrel (200 liters capacity) 6 NO SteelAluminumWooden ladder (35m length) 5 NO 30 m metallic tape 1 NO 30 m steel tape 1 NO Engineersrsquo spirit level 2 NO Steel piano wirethread 50 m Crow bar 20 NO Pick axe 12 NO Spade 25 NO Shovel 8 NO Gamelas 30 NO Buckets 12 NO Iron rammer (45 Kg) 5 NO
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 44
Masonry trowel 6 NO Manila rope ‐ 38 mm dia 150 m Manila rope ‐ 12 mm dia 30 m Poking rod (16 mm dia) ‐ 3 m length 2 NO Poking rod (16 mm dia) ‐ 15 m length 2 NO
Blasting materials binding wire As per
requirement
Hammer Tommy bar plumb bob (045 Kg) Hook (12 mm dia) spanners (both ring and flat) etc
As per requirement
Tents buckets water drums camping cots Tables and chairs petromax etc
As per requirement
Transport required for Stub‐setting amp Concreting Gang Truck (For transportation of metal and sand from Source cement reinforcement steel and Other materials from site stores)
1 NO
Tractor with trailer 1 NO Motor cycle 1 NO
74 Tower Erection
bull Tower erection requires lot of precision Besides the material has to be lifted from the ground level to various heights depending upon the type of tower While erecting it is necessary that equilibrium is maintained and damage to the tower material and accidents are avoided The infrastructure required for this activity is given under
bull Average output per gang considering of about 50 crew members per month will be ‐ 80 MT bull Tools required for Tower Erection Gang
Ginpole Derric Pole ‐ 75100 mm dia amp 85 ndash 9 m length 2 NO Polypropylene rope ‐ 25 mm dia 700 m Polypropylene rope ‐ 19 mm dia 1000 m Single sheave pulley ‐ closed type 8 NO Single sheave pulley ‐ Open type 4 NO Crow bars (25 mm dia amp 18 m length) 16 NO Spanners (both ring and flat) Hammers Slings (16 mm dia amp 1 m length) Hooks (12 mm dia) lsquoDrsquo shackle tommy bars
As per requirement
Tents buckets water drums camping Cots tables chairs petromax etc
As per requirement
Transport required for Tower Erection Gang 1 Truck 1 2 NO 2 Tractor with trailer 1 NO 3 Motor Cycle 1 NO
75 Stringing Stringing work is almost the last activity save commissioning in the overall construction activities in the EHV transmission lines This is really a very precise and hazardous activity While stringing operations are on load balance and rigging arrangement has to be full ndash proofThe man power deployed has to be proportional to the actual physical tension
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 45
required to be given to the earth wires and conductors Excess man power may result into over tension and less man power may result into improper stringing and accidents The infrastructure required for stringing operations is given under
bull Average output per gang consisting of about 200 persons per month with Tension Stringing ndash Machine stringing method For 400 KV single circuit 15 km For 400 KV double circuit 8 km For +‐ 500 HVDC multi circuit 5 km
bull Requirement of man power and average output per gang for carrying out various types transmission lines by manual method is furnished here under Description of line Man power (NO) Average output month (km)
bull Tools and plants required for stringing Gang for TensionManual Stringing
TSE sets (Tensioner and Puller of 810 T capacity) 1 SET Running block for conductor 100 NO Running block for earth wire 60 NO Head Board 2 NO Pilot wire each of 800 m length 10 NO Pilot wire joint 12 NO Ground roller for TensionManual Stringing 30100 NO Wire mesh pulling grip (one end open) of required dia for conductor
6 NO
Wire mesh pulling grip (one end open) of required dia for earth wire
2 NO
Wire mesh pulling grip (double end open) of required dia for earth wire
4 NO
Articulated joint ndash Heavy duty (20T) 10 NO Articulated joint ndash Medium duty (10T) 10 NO Articulated joint ndash light duty (5T) 5 NO Drum mounting jack for conductor drum of 10T capacity 4 SETS Turn table (5T capacity) 2 NO Anchor plate (15 m x 10 x 8 mm) with 15 Nos anchor pins (45 mm dia amp 850 mm long)
Hydraulic compressor machine 100 T capacity with die sets 8 NO Traveling ground 12 SETS Dynamometer ‐ 10T 4 NO
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 46
Dynamometer ‐ 2 T 2 NO Pilot wire reel stand 4 NO Four Sheave pulley with 12 mm dia 300 m length wire rope 6 SETS Four sheave pulley with 9 mm dia 300 m length wire rope 2 SETS Four sheave pulley with 12 m dia 150 m length wire rope 4 SETS Equalizer pulley (10 T) capacity 16 NO Conductor lifting tackle 4 SETS Winch ndash motorized manual ndash 10 T capacity 4 NO Come along clamp for conductor (bolted type automatic) 5020 NO Come along clamp for earth wire (bolted type automatic) 1510 NO Tirfor (5 T capacity) 6 NO Aerial chair (For conductor) 6 NO Aerial Trolley 4 NO Turn Buckle ‐ 10T 16 NO Turn Buckle ‐ 3 T 6 NO TensionSag plate (for tensioning purpose) 6 NO Sag Board 8 NO Marking roller 4 NO Mismatch roller 2 NO Joint protector 6 NO Walkie talkie set 4 NO Theodolite with stand (or Total Station with Prism) 1 NO Thermometer 3 NO Survey umbrella 1 NO Hydraulic wire cutter 2 NO Binocular 3 NO Flag (red and green) 30 NO Crow bar (18 m length) 10 NO Nail puller 6 NO Wire rope ‐ 19 mm dia 1000 m Wire rope ‐ 16 mm dia 150 m Wire rope ‐ 14 mm dia 900 m Polypropylene rope ‐ 25 mm dia 500 m Polypropylene rope ‐ 19 mm dia 500 m lsquoDrsquo ndash Shackle ‐ 190 mm long 40 NO lsquoDrsquo ndash Shackle ‐ 150 mm long 125 NO Bulldog clamp ‐ 100 mm long 125 NO Bulldog clamp ‐ 100 mm long 35 NO
Hammers spanners (both flat and ring) round files flat files screw drivers cutting pliers steel and metallic tapes hacksaw frame and blades scaffolding slings etc
As per requirement
Tents buckets water drums camping cots table chair petromax etc
As per requirement
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment
Power Consultants amp Agencies Page 47
76 Transport Required for Stringing
Tension Stringing Manual Stringing Truck 4 NO 4 NO
75 hp tractor 2 NO 1 NO
35 hp45 hp Tractor and trailors 5 NO 6 NO
Jeep 2 NO 2 NO
Motor Cycle 1 NO 1 NO
80 Conclusion 81 Construction of EHV transmission line is a very precise and skillful job Proper construction practice ensures high reliability and long life of the transmission line 82 The main activities of foundation tower erection amp stringing are completely diverse from each other and require different type of skill workers as well as tools tackles and equipment