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Mission Statement
Mission
Our Mission is to provide our customers with high quality electricity and water services, whilst creating value for our shareholders.
Objectives
Our objectives are to:
Efficiently meet our obligation to supply Qatars need for electricity and water.
Operate on a commercial basis.
Comply with local and international health, safety, and environmentalstandards.
Maximize the employment of capable Qatari nationals and develop them tothe competence level of employees in leading international companies.
History
Introduction
Qatar General Electricity & Water Corporation,was established in July, 2000f th t th E i i L b 10 t l t d i t i l f
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f th t th E i i L b 10 t l t d i t i l f
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The Board of directors at Kahramaa is granted extensive authorities toachieve the corporation’s goals mainly, the setting, and implementation and
follows up of general policies, plans, programs and projects.The board main responsibilities are the approval of corporationsorganizational structure, endorsement of the financial, administrative andtechnical internal rules and regulations, employees policies and regulations,as well as approving the corporation investment plans, its annual budgets andclosing fiscal year and approves loans with the Government and other parties,in addition to review of the operational and strategic performance.
b. The Financial Resources
The main financial resources of Kahramaa is the annual allocated funds fromthe state (government), services fees and revenues, the return of its capitalinvestments on its assets as well as the value of its shares and loansextendedtoothers.
The Electricity Sector
The Electricity transmission networks consist of approximately 100primary High Voltage sub-stations with total 660 km of overhead linessupported by 600 km of underground cables across the country. Thenetwork is coupled with 6500 low and medium voltage sub-stations(11kv) and more than 4500km of cable lines.The National ControlCenter (NCC), which contains state-of-art technologies, manages allnetwork demand and data acquisition from generation plants and
primarysub stations
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GENERAL OVER VIEW
Kahramaa distribution Network consists of about 10000 Nos substation. They
are either Indoor type or Out door type.
Max demand - 3025 (27.06.2006) till date
The domestic consumption is more predominant in the system and domestic
load contributes major portion of the total demand. Remaining are industrialand they contribute very less, near about 15% of the load (approx. 450
mw).Seasonal variations are predominant because of the extreme climatic
conditions. In summer, hot season begins from May – September, the
demand reaches its maximum value But in winter season, (Nov- Feb), the
demand reaches its minimum value.
In summer season demand is about 3000 MW
In winter season demand is about 1000 MW
But the Repaid economical & industrial development brings, Qatar power
sector a demand growth of about10% every year.
KAHRAMAA’S distribution Network consists of about 10000 Nos substation.
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3) Outdoor Substation
4) Under ground cables5) Over head lines - OH/L.
1) Primary Substation
Main incoming supply to the Primary Substation is fed from 66
KV system. Two main incoming transformers are generally provided to feedthe 11 KV Distribution system. 11 KV Bus is provided with a Bus
Coupler(A120) for oparational flexibility and is normally in closed condition..
All Switchgear panels for incoming feeders,transformers and outgoing feeders
are equiped with Circuit Breakers,Isolators and Earth switches. Current
transformer and Voltage transformers are also provided in each circuit for
protection & metering. Earthing transformers are provided for stable neutral
and for station supply. Circuit breakers are of either VCB/SF6 / OCB types are
used.DC System is 110 V DC with Battery and Charger. The primary
substatoin are well equipped with Control panel,protection panel,Switch gear
panel and Axilliary facilities. Local and remote control is possible for all
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Selector switches are in Grid position where Out going feeders are in DCC
control and Incomers and Bus Coupler are in NCC control.A Senior Authorised person can change the Selector switch position for work only with
the consent of Contrl Engineers of NCC/DCC.
2) Indoor Substation
All Indoor Substations are well equipped with Switchgear panelswith Circuit Breakers,isolating & eathing facility,control and protection circuitry
and metering facility for the smooth operation and control of feeder and Local
distribution transformers. All Feeders and L/Tx are connected to the common
bus of the Indoor substation through the respective circuit breaker. DC
system available is 30V DC with Battery and Charger.Station LT supply for
station lighting and Battery Charger is taken from L/Tx. All of the switchgeer
panels, L/Tx and Communication systems are protected inside a room.
Circuit Breakers used
1) OCB- Oil Circuit Breaker –Oil (Medium)- Vertical isolation
Types available are
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Control and protection circuitry is provided with the Switchgear panel
for the control and protection of Feeders and L/Txs.Local control facility isonly available for CB.
Metering
Ammeters are provided in each circuit to measure the load current
Status indicators are provided for circuit Breakers
DC voltmeter is provided to measure the DC voltage.
Operation and Maintanance
Presently no remote control is possible. Local operation &
Maintenance is always done by the Field engineers(Senior Authorised
Person) of Distribution Department with proper consent from System Control
Engineer on duty.
3) Out Door Substations
In Outdoor substations, Main Switches and Transformer
switches along with Earthing facility is provided for oparational, maintanance
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Main Switches for Feeders
Earth Switches for Feeders and TransformersTransformer Switches (OFS & TXS)
Current Transformers provided for EFI
Local Transformers - 11KV/433 V
Bolt on Feeder Pillar (BOFP) /Free Standing Feeder Pillar (FSFP)
HT and MV cables.Earth fault Indicators
Gas Pressure Indicators (only in SF6 Outdoor s/s)
Classification according to Insulation Medium
In outdoor s/s, all feeder switches and TX switches are provided with either oil
or SF6 Gas as insulation medium for breaking/making load current.
Oil Switches:- Oil is used as insulation medium for breaking /making the load
current. All switches are rated for breaking/ making load current and not
intended to break /make the fault current.But for transformer circuit Oil Fuse
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the CT across a shunt coil. Normal condition the current will flow through the
TLF( low impedence path) Any abnormality comes the fuse will blown out andit will results the flow of current through the shunt coil (high impedence trip
coil) which in turn trips the circuit breaker.Different types used are :-
Tamco
Merlin Gerin
ABBW Lucy
Fuse rating for different rating transformer
Oil Fuse rating available - 40A,63A,70A& 90A
Standard TLF Rating available – 5A,7.5A,10A,12.5A &15A
Voltage Transformer
Voltage Transformers (VT) are provided for metering, protection and
synchrocheck. VT is always part of Cable and is provided in all Primary
substation and in some Indoor Substation.In Primary all Feeders ,Incomers
and Bus sections are equipped with VT. VT’s are consider as part of the
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Ring Main Unit(RMU)
A single unit with two feeder switches and one T-off transformer switch. Oil and SF6 switches are available. Only one Transformer
circuit is available .Normally Transformer is connected to the T-off circuit and
two feeder switches provided on both sides.
Semi Extensible RMU
The outdoor substation with one RMU unit and which has a
provision to extend its Bus bar towards one side to add more circuits (Feeder
Switches/Tx switches) depending upon the Bus Bar current carrying
capacity.The extensible side of the RMU is provided with an Endcap.
Extensible RMU
The outdoor substation with one RMU unit and which has a provision to
extend its Bus bar towards both sides to add more circuits (Feeder
Switches/Tx switches) depending upon the Bus bar current carrying
capacity.Endcaps provided on both sides.
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•Main Switches are intended to making /breaking load current only andthere is no associated protection circuitry. These switches are not
designed to break / make fault current.
• Status indication windows are available for Main swtches,Earth
switches and TXS to indicate the current status of operation.
Main Switch Closed condition - "ON" with red backgroundTX Switch Closed condition - "ON" with red background
Earth Switch Closed condition - "ON" with yellow background
Earth Switch /Main Switch /TX Switch - Opened condition -
"OFF" with green background
•TX Switches are provided with Oil Fuse/ TLF for tripping the circuitunder overload / abnormal condition.
Inter locking
1) Inter locking facility is provided between Earth Switch ON and Main
S it h ON diti
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Manual type –Manual reset is required after the Flag ON condition due to fault
Auto type - LT supply is provided to EFI and it automatically reset the Flag
due to the fault after a delayed time period when supply resumed.
Gas Pressure Indicator for SF6 RMU
The Gas Pressure Indicator reading should be in the green zone for the safe
oparation of SF6 RMU.
Filling Pressure at 20 degree cent.- 0.4 BARG
Minimum oparating Pressure - 0.05 BARG
Red zone - operation of RMU is not allowed.
Green zone - Operation is allowed
If it is in red zone, refilling is required for further operation and is allowed only
with PTW.
HV and MV cable of Distribution Transformer
11KV HT Single run 3 core cable connect the TX Switch to the Transformer
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Bus Bar (R,Y,B and Neutral)
MV side cut out fuses ( 100A,200A,315 A)MV outgoing Cable (4 or 6 circuits)
Eatrhing Bus
Current Transformer
In Feeder Pillar MV links are provided for LT Outgoing Cables (3 Phase 4 wire
with separate Earth wire ) HRC fuses are provided in LT cable for overload
protection rating depends on the load current. In some consumer MV panel is
available with ACB and REF protection.
Maximum Demand Indicator
Ammeter is provided in MV panel with two needles. One is for the real
time load current measurement and the other one is for all time Meximum
Demand.This indication is more usefull tripping/fault analysis.
LT Transformer – ( 11 / 0.433 KV ) Dyn 11
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- Cut out fuses are provided depending upon the load.
Safety during shut down• The working section should be dead , isolate & Earth at both ends
before doing any work
• Test OH/L line before starting work by using an HV Tester for
confirmation
•If the OH/L found Dead,apply Portable Earth at the point of work
• Always instruct the workforce to wear
Safety Belt
Safety Shoe
Helmet
Gloves
• Field Engineer should collect the original copy of safety document
(PTW) signed by the competent person
• OHL work should be stopped immediately when the atmosphere
b l d d h f li ht i d th d h
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- A visual check is reccomended after each operation whether the
contacts are properly inserted/seperated.- Arcing Shields are provided to minimise the arcing of blades.
- If ABS is deffective , jumper connections are used to bypass it.
Test OH/L, If Dead, Apply Portable Earth
An HV OH/L Tester used to test the isolated line to make sure that the line is
electrically Dead and is always applicable before applying Portable Earth to
commence a work. After isolating & earthing( if facility is available) both ends,
then test the OH/L , If found dead apply Portable Earth at the point of work by
a copetent person with the precense of a senior authourised person.
If the OHL is dead - tester making normal low beep
If OHL is live - tester making high beep
( Before and after the tester itself should be check )
Portable Earth(PE):-Before doing any kind of work on OH/L, the Portable
Earth must be applied at point of work and is very essential to give a Permit to
Work(PTW) . So before issuing PTW, the System Control Engineer should
confirm that the PE is applied at the point of work and simillarly he should
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• Drop Out fuses are provided for the transformer
protection.Replacement of D.O fuses is permitted under live condition..• Out going cable with Fuse Cut – outs are used to feed the LT 3phase 4
wire system. Ratings available are 100 A, 200 A , 315 A .
• Earthing arrangement for PMT – Normally two Earth pits are provided,
one for ground /Body Earthing and the other one is for system neutral
earthing.Pole Box
Termination in a pole which provides connection between OH/L
circuit and UG Cable circuit is called a Pole Box. The HT cable may be either
from any I/D Substation / Out Door Substation or from another OH/L portion
due to crossing of road / EHT line.• CT and Earth Fault Indicators are provided in some Pole Box to
indicate earth fault passage
• LA’s are provided to protect the cable termination from lightning surges.
• Separate Earthing is needed for pole Box.
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point of isolation. According to the operation and control, two types of
Recloser are used in OH/L System. Auto reclosers with manual control
During fault, the auto recloser trips the circuit. But after the first opening, the
recloser attains Lock-Off. Manual operation is needed for closing the Auto
recloser and this is done by using an insulated operating rod. First the
operator should manually reset the switch and then close.
Auto reclosers with auto control
A microprocessor control is provided along with the Auto recloser and is
mounted on the pole (bottom). The operator can operate it from the ground
itself. This type of Auto recloser trips the OH/L faulty section and attains to
lock off. Closing after patrolling and clearing the fault is possible from the
automatic control installation. This type of auto recloser should protect the
OH/L section from O/C, short circuit, E/F and sensitive E/F.
Main Components
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RAS ABU ABOUD - 107 MW
SATALLITE STATIONS
i. AL WAJBAH
ii. SALIYAH
iii. DSS - 473 MW
Q- POWER - 699 MW
TOTAL 3528 MW
Transmission network
Kahramaa transmission grid consists of the following voltage levels.
Transmission Network
220 KV
132 KV
66 KV
Distribution Network
11KV
0.433 KV
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The National Control Centre (NCC) controls the QGEWC’S power
system in an efficient way. The smooth, stable and efficient grid control is
achieved by the automated control system (SCADA / EMS). Two control
desks are available, they are (I) Generation Desk and the other is (ii)
Switching Desk.
(i)Generation Desk.
Controlling the Active and Reactive power flow to maintain the
system voltage & frequency to a predetermined value.
Act according to the surplus & deficit condition.
Act according to the abnormal condition.
Merit Order Dispatch is observed
Automatic Generation Control is in operation.
(ii) Switching Desk.
Coordinating & controlling to all Switching operations.
Give Sanctions ( PTW & SFT ) to all switching operation
Executing load rearrangement programmes during shut down /
abnormal conditions.
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A spinning reserve equal to the capacity of the largest unit in service is
to be maintained as far as possible.
Operation with less than above or zero spinning reserve is allowed
when there is a short fall of generation capacity during summer peak,
or due to agreed plant maintenance programme, or units purposefully
kept off to avoid plants running winter nights or when generation unit
are agreed to be kept stand by ,to save running hours for anticipated
usage in next summer peak.
Voltage Control
(I) Generator MVAR Control
System Voltage is maintained by controlling the reactive power flow.
Due to the highly inductive nature of load, a larger capacity of MVAR is
required. The main MVAR generation source is the generator and all
generators are normally supplying about 50% of the active power as MVAR.
Then the major source and control point of MVAR is generator source.
Voltage is maintained by controlling the MVAR output of generators. The VAR
control can be achieved either through SCADA control or by local control.
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Immediate improvement in voltage to a limited extent is possible by changing
the tap of transformers in the system.
The Remote tap changing cubicle (RTCC) is having different ways of control.
They are:-
(i) Automatic control (with AVR)
(ii) Supervisory control (NCC)
(iii) Manual control (local)
For Grid Transformer - control is done from the NCC (supervisory mode only)
- ON Load Tap changing is possible.
For Primary Transformer (66 / 11KV) – Automatic control mode operation is
enabled with AVR(ON Load Tap Changing)
For Distribution Transformer – OFF load, manual control only permitted.
Operation at Abnormal Conditions
There are generally two conditions where the system runs on bellow target
frequently.
Condition 1 - When all the plants on bar (POB) are fully loaded and the
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if necessary this is continued with next list and so on. Next load shedding list
for cyclic shedding is # 23.
Note: DCC should be informed before domestic shedding, and they inform the
stand by offices concerned. Maximum load shedding time is limited to 2 hrs.
First domestic load and then furnaces are restored and later import of energy
is stopped as frequency improves.
Condition 2 - A Sudden drop in frequency due to an unexpected major
generation loss. This is an unanticipated frequency drop situation.
Action required – In this case automatic under frequency load shedding takes
place at various stages.
1. Automatic under frequency Bulk load shedding.
2. 11KV feeders at Primary s/s (domestic load) are kept selected at
predetermined frequency levels as below for automatic shedding.
Stage 1 A - Setting 49.2 HZ
Stage 1 - Setting 48.8 HZ
Stage 2 - Setting 48.4 HZ
Stage 3 - Setting 48.0 HZ
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Objective
Monitors and ensures continuous electricity supply for the distribution
network, within the prescribed values of limit violations, giving priority to
security and safety.
Major functions
Controls Active & Reactive power flow in the network and there byregulate the voltage.
Confirms to all the operation are done in strict compliance with the
department safety rules and regulations and there by ensuring system
safety and security.
Control , coordinate and direct to all switching operations by givinginstruction to field engineers for switching in the 11 KV network for
maintenance / repair of network components and for after fault
restoration.
Co-ordinate with NCC, in case of generation shortage or other system
contingency to shed the load in accordance to the prearranged
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Breaker status are transferred to DCC for monitoring and controlling. It also
provided alarm and limits violation condition to remind the Control Engineer to
act accordingly. The available data’s in the DCC computer console can be
utilized to originate different report for the smooth functioning of DCC.
Available Data’s & facilities
Loading Values of different Primary transformers.
Loading values of different outgoing feeders of PRY
Bus voltages of PRY
Breaker and VT status of PRY
Limit violation, alarm and important events.
All the data’s available in the DCC console can be utilized for past and
present system analysis and also helpful for the contingency analysis. The
data’s available in the database also helps to originate various technical report
& statistics.
Role of System Control Engineer
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Check whether all the safety aspects are taken care of before
execution.
Study the load rearrangement during the shut down, possible way of
back feeding, loading values of feeders and Transformers involved.
Check the load of feeders involved in paralleling at the time of
isolation and live phasing.
Analyze the paralleling involved in the programme and check
whether it is a bad paralleling or not.
Scrutinize the point of isolation, back feeding arrangement in terms
of system security and safety.
Study the loading condition due to the shut down and check whether
the shut down causes any overloading to any feeders and primary
transformers involved in the programme.
Check the substation planning Number and Name, Sequence of
operation and safety aspects related to the programme, date of
execution and duration of shut down etc.
Study the Live phasing route ,loading during Live phasing and
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Check the load of feeders involved before paralleling.
Check whether it is a bad paralleling.
Check the bus voltage of the Primaries involved.
If possible, request NCC to minimize the voltage difference
between Primaries involved.
Block the tap changing in order to avoid furthers changes in
voltage and thus the unwanted circulating current. This will
minimize bad paralleling effect.
If there is a bad paralleling history then arrange two field engineers
for make & break operation (if possible) or break and make
depending upon the consumer affected.
Check the load on feeder involved after paralleling in order to
confirm the paralleling is successful and is not interrupted the
consumer.
Supply confirmation from the field engineer is very essential after
paralleling.
• Before energizing a transformer, study the present loading of feeder
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• For collecting additional information about the tripping, the Control
Engineer can utilize the help of SSA and Stand by Technicians.
• Convey all information collected to the Distribution Stand by Engineer
and also give the Tel. No. of SSA who attending the fault. Control
Engineer should instruct the field engineer to proceed to the Indoor /
Outdoor / PRY where the fault is suspected.
•If OH/L is involved, then inform ABU HAMUR OH/L section to arrangethe patrolling.
• Report the matter to the top officials with details.
• Study the possible back feeding arrangement.
• Collect all information from the SSA at site and from the Stand by
Engineer like relay indication, EFI status, station supply (Battery) andabnormalities etc.
• With the above information locate the fault as early as possible.
• While test charging, keep the relay time setting to the minimum.
• Isolate the faulty section, apply C/N, L/ off and apply CME at point of
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• Always tell the name and planning No. of location and circuit to the
Engineer.
• Note down the time of instruction and time of confirmation of operation.
• Before issuing PTW and SFT confirm that the working section is
isolated, Earthed at both ends. And also confirm that the S/L and C/N
applied at the point of isolation.
• Always confirm switching positions after cancellation of SFT.Confirming switching positions after SFT is mandatory because of the
Field Engineer has the approval for the operations of earth switches
under SFT. He has the temporary control over Earth switches during
SFT for the purpose like HV injection, signal injection, colour phasing
etc.
• If OH/L involved in the isolated section, apply CME at point of isolation
(if possible) and test OH/L line, if found dead apply Portable Earth at
the point of work. After confirming the above, issue PTW. Before
cancellation of PTW confirm that all CME and portable earth are
removed from the line.
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• When multi permits issued to the same Field Engineer or to different
Field Engineers within the same point of isolation, then the energisation
shall be done only after the cancellation of all holding PTW’s within the
isolated section. When multi permits issued to different field engineer,
cross reference numbering is recommended (# CR).
• A field engineer can’t hold more than one SFT at a time. SFT is issued
by the field engineer to himself and his direct supervision involvement
is required to perform the test.
• Proper informational tags must be placed on single line diagram to
avoid any wrong operation.
• The field engineer can’t suspend the SFT. He has to cancel SFT before
he leaves the site. Any inconvenience occurred to complete the test,
then he should cancel the SFT and also confirm the switching positions
before the leaving the site.
• The field engineer can’t hold PTW and SFT together.
OTHER IMPORTANT ACTIVITIES
Load shifting / rearrangement as per NCC advise.
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In case of PMT, remove the HT fuse and then adjust the tap
position as required.
NOP Shifting:
Paralleling between same or different sources is required
Different Situations:-
• Load balancing among same or different Primary transformers.
• Load balancing among Feeders.
• During shut down works – to back feed the load to avoid interruption.
• During fault restoration.
• To avoid over loading of Feeders and Transformers.
Important Considerations required
Before paralleling, study the voltage profile of sources and block thetap if required.
Before and after paralleling study the real time loading values of
Feeders and Transformers involved.
Always confirm the supply status and this is necessary to find out
any load loss due to tripping in between.
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3. PTW and SFT Cards.
Prepared in prescribed form separate for PTW and SFT and which is serially
numbered with brief details particularly about CME, Name of Engineer,
Section isolated, work, Date and Time etc.
4. Station Log
All events recorded by the Control Assistant in a chronological order during
the shift. This includes all the switching operation instructions given by the
Control Engineer.
5. Control Engineer Log Book
Brief reports about the Operations during the shift.
6. Daily Report – system statistics
7. Weekly Maximum Demand Log
8. Daily peak print out.
Communication facility available
Q-Telephone, KM’s Pax phone, Hot line telephone and Fax
Construction & Reinforcement section -Distribution,
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section after obtaining the proper consent from governmental authorities. ROA
wing should arrange the approval from the governmental agencies (Qtel,
Sewerage, Civil engineering Department, Road Division and Water
Department of Kahramaa).
Role of Construction Engineer
• Estimates the material requirement and coordinate the same with the
suppliers & ABUHAMUR work shop• Coordinate with consumer for execution of scheme
• Allocate the work to different contractors and coordinate with them for
final execution.
• Prepare an action plan for the proposed work.
• Prepare shut down notices before execution, if any supply interruptionanticipated.
• Prepare switching programme for shut down and Commissioning. The
switching programme along with the alteration proposed to the existing
system is required to get proper consent from the system control (DCC)
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• The system control engineer should arrange for possible back feeding
and load transfer in order to avoid interruption during the execution of
work.
• The switching programme and other activities involved during the
execution shall comply the Safety Rules and Operation memorandum
of QGEWC high voltage system. The system operation memorandum
D15 is followed in this aspect.
• Before Commissioning a New Substation / Transformer
- Check the new label and fix it properly and confirm the same to
control (DCC)
- Protection and fault level of CB. Verify and inform to DCC.
- Check the operation of CB.
- Check the station lighting
- Check the trip circuit healthiness
- Check station Battery and Charger.
- Check the transformer before energizing (oil check, tap setting,
name plate, abnormalities etc.)
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1. Cable Identification.
2. Spiking
3. Colour phasing ( core phasing )
4. 11 KV Jointing work & Termination work on HT cable )
5. HV pressure test for 11 KV cable and Bus Bar
6. Dead phasing check – 11 KV system
7. Live phasing check - 11 KV system
8. Phase rotation check for MV side.
9. MV voltage check.
10.Trip / test check for CB.
11.Relay inter trip check
12.Transformer, Switchgear panel, Switches and Substation observation.
13.Relay setting & fault level.
Cable Identification
During construction and maintenance, the existing cable has to be cut
for fault rectification and for commissioning new substations in between the
existing cable. Then the Field Engineer should confirm the cable which is
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after removing the earth. Keep remote end of cable as earthed for return path
.Then by using the Audio receiver and head phone, we can identify the cable
in which signal is generated. When the receiver is put nearer along the cable
gives a clear beep but varying sound from the cable trough which transmitted
the signal. Sound variation is obtained only from the injected cable due to the
twisting of cable pairs. But for other cables, humming sound is obtained from
live cables and clear beep but not varying is obtained from dead cable if any.
The Cable Identification test is done by the field engineer himself in charge of
work. See the figure.
Spiking
After identifying the cable, before cutting, spiking has to
require for 100% confirmation that the cable is absolutely dead and safe for
cutting. Spike gun is a special arrangement, where the iron bullet is used for
firing. The spiking gun with bullet is placed over the cable and firing is done
remotely with the help of a rope. If the cable is the correct one, there is no
heavy sound. But for live cables heavy flash over and tripping may occur.
Thus spiking will helps to avoid dangerous situation and it provide more safety
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of jointing / termination works to transfer the same system phase(R, Y, and B)
from one point to other point. Colour crossing of the cable is serious and to
avoid this colour phasing is required during jointing and termination work.
Different methods for colour phasing
1. Banana Resistance and Megger
Connect the three different resistances (known value) to the RYB phases of
one cable end (Star connection with star point earthed) then by using a
Megger, which connected to the other end of cable and measures the
resistance. The corresponding values of resistance obtained on phases will
give the correct phase.
Uni directional LED with Battery set.
Connect the battery between any two phases of cable at the known end. Then
the lamp glow will indicate the phases where the battery connected and it also
indicate the direction of current flow. Then from the lamp glow and direction
we can easily confirm the three phases.
Safety
Before doing test, the cable should be isolated, earthed at
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together for same point of isolation is not permitted. If PTW is issuing after the
SFT, then the Control Engineer should always confirm the switching position
and also confirm that both ends of the cable is isolated and earthed.
Competent person - Kahramaa certified HV Cable jointer / Fitter with
Identity card of Kahramaa
Straight joint kit - XLPE cable to similar XLPE or PILC to similar PILC
Transit joint kit - XLPE cable to PILC or PILC cable to XLPE
Dead joint - Jointing work on Dead cable
Breaking a Termination – Removing an existing cable at a termination point
Making a Termination - Connecting a new cable at a termination point
Break & Make Termination - Breaking and making termination of cable at a
Point during construction / maintenance work
Safety
Before doing any work on cables, the cable section must be
isolated & earthed at both ends.
Any work on cables like Break & make terminations, Cable
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between Phases(R-Y, Y-B, and R-B). The duration of HV injection is about 15
minutes for each test. Pressure test is also required to test the perfection of
terminating & jointing work.
Pressure Test Kit
In the testing instrument, meters are provided to indicate the applied KV and
leakage mA of the circuit. If the leakage current value during injection is in
between 0.1 and 1.5 mA, then the cable is declared as healthy. The leakage
current higher than 3mA indicates the breakdown of the circuit. That means
excessive leakage current or tripping indicates that the dielectric strength of
insulation, jointing work / termination work is not up to the standard. If there is
a new bas bar is involved in the circuit, then HV Pressure test for Bus Bar is
also compulsory. For safety, discharge rode is provided with the test kit to
discharge the capacitive charge of cable after the test.
Phase to Earth Test
Voltage applied = 11 KV DC (Negative)
(R-E, Y-E and B-E)
Duration - 15 Minutes
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After the Pressure Test, the SFT taken should return and cancelled
with the consent of system control engineer. Confirm switching
position is mandatory.
11 KV DEAD PHASING
This is a method of checking R, Y, B, phasing of the newly constructed
elements from known end to the other end before live phasing. Dead phasing
will not disturb the existing system. This is a pre - confirmation test before live
phasing.
11 KV LIVE PHASING
After all type of constructional / maintenance activities on cables,
terminations, the 11 KV live phasing is required. This is essential for meeting
same RYB sequence condition before paralleling between two systems. It
always conducted at I/D substation and it prove that the added network
elements in same phase sequence with respect to the existing. The I/D
Substation nearer to the newly commissioned Substation should be taken in
order to minimize interruption to the consumers.
Live phasing proving the there statements below:-
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Bar spout phases and the Cable spout phases. While observing the live
phasing between the two system available at Bus bar spout &
Cable spout, for correct live phasing the voltage should be as follows:-
R of (Bus bar spout) to R (Cable Spout) – 11 KV
Y of (Bus bar spout) to Y (Cable Spout) – 11 KV
B of (Bus bar spout) to B (Cable Spout) – 11 KV
R of (Bus bar spout) to Y (Cable Spout) – 5.5 KV
Y of (Bus bar spout) to B (Cable Spout) – 5.5KV
B of (Bus bar spout) to R (Cable Spout) – 5.5KV
If any mistakes happened during work, then the voltmeter will indicate
incorrect reading. Then the Field Engineer should rectify the mistake.
At Indoor substation, the CB towards the new circuit should be kept opened.
Then Bus Bar spout is having the existing supply and cable spout is having
the existing system through the new circuit. By inserting live phasing sticks
between bas bar spout & cable spouts, we can confirm whether the live
phasing is correct or not.
Safety during live phasing
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bad paralleling etc. We can conduct live phasing at any I/D substations
( existing or new one )
• If the supply is taken through the new circuit includes an existing O/D
substation, then the existing and new phase rotation has to be check
for consumer safety.
Phase Rotation & MV voltage check for MV side
11 KV live phasing only proving that the new HT network elements are
in correct phase with respect to the existing system. But for transformers MV
phase rotation & voltage check is required to ensure that the consumer supply
is not affected due to the alterations and modifications done during the work.
This is required to ensure proper MV voltage and phase rotation to the
consumer.
Methods
1. Phase Rotation meter
2. LED Flickering meter
Phase rotation can be checked either by using a phase sequence check
meter (rotating dial with arrow indication) or by using an LED flickering
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LT side fuse replaced only after the successful commissioning of
transformer.
Close, Trip-Test and reclose
Trip-Test
If any CB is Rack out for any operational purpose, then it must be checked for
trip test. This is for a confirmation that all the auxiliary contacts are healthy as
before. Trip test is done by rotating the disc manually and it ensure the
following
Circuit Breaker auxiliary contacts are healthy and okay as before.
Trip circuit is healthy.
Close
If the live phasing is correct, for proving the same the Field Engineer
should close the CB between two systems.
Reclose
After proving the live phasing, the system NOP should be as per the
direction of System Control Engineer. That means the close or reclose is
according to the system condition.
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- Trip circuit healthiness.
Panel - Circuit labeling.
- Meters to be check for its functioning.
- provide operational locks.
- relay setting & trip circuit status.
Substation and Switchgear room - Planning Number.
- Door Lock.
- DC Battery Voltage check.
- Battery charger healthiness.
- Station lighting.
Operation & Maintance section, Distribution, Kahramaa
Introduction
The smooth functioning of distribution system is always in
accordance with the performance of its operation & maintenance team. So
continuous and reliable supply is ensured only through the better and efficient
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i. Preventive Maintenance: - Preventing a future breakdown and
ensure continuous supply. All periodic scheduled maintenance
on the 11 KV Distribution system is comes under this category.
Regular systematic maintenance, all preventive action taken for
the smooth & efficient operation of the system. Servicing,
Overhauling and routine oil and gas check are examples.
ii. Corrective maintenance or Breakdown Maintenance:- This is the
corrective actions taken for the smooth and efficient operation of
the system. The Break down or corrective maintenance
activities are conducted after the failure of an equipment. Such
maintenance results in outage of circuit and supply. In general,
it consists of locating the trouble, repair and recommissioning.
General duties of O&M Field engineers
All switching operations for O&M work are done by field engineers on duty
1) Periodic repair & maintenance – Preventive works-oil /gas
changing, servicing etc.
2) Break down Maintenance -TX replacement, Faulty Cable
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(DCC). So for all the work (operational, repair and maintenance ) the field
engineer should obtain proper consent from System Control Engineer (DCC).
Immediate supply Restoration:-
Immediate supply restoration always gives better service to
consumers and is important in distribution system. The kahramaa distribution
system has adopted an efficient and effective way for overcoming the
emergency breakdown condition. The field engineer are posted on a round
the clock rotation basis for the stand by duty in order to attend the emergency
tripping conditions and restoration thereon. During the tripping and emergency
condition, the system control engineer should co-ordinate and directs the field
engineers for immediate restoration. The system control engineer should
direct and co-ordinate by giving instructions to the field engineer as per the
relay indication and other field information. First, he should find out the faulty
portion and then isolate it from the healthy system and then restore the
remaining healthy system as early as possible. After that, DCC Control
engineer has to direct and coordinate the field engineer to rectify the faulty
section as early as possible. All the above switching operation must be done
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provided for some important distribution consumers. But mostly all I/D and
O/D substations are feeding from one source at a time and there is always
one or more alternative sources (either from same or different PRY) are
available as NOP. Some Radial feeding s/s and multiple source feeding s/s
are also available (same primary). The location of NOP decides the loading of
the 11 KV feeders which in turn reflects the loading of the transformers of the
Primary Substation.
NOP shifting will always helps to balance the loading among 11 KV feeder/
primary transformers and also helps to back feed the system at the time of
supply failure. There NOP shifting can be execute either by a pre-planned
manner (prior switching programmers) or for an emergency situation like over
loading / tripping of feeder / transformer (PRY). If it is in urgent nature, then
the field engineer on stand by duty has to attend the NOP shifting. The pre-
planned NOP shifting programme is normally executed by the field engineer
on system operation duty.
For system operation load shifting (NOP- Shifting), the DCC
should prepare the switching programme and the switching is
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Stand by offices are under the system operation department (DCC).Their
primary duty is providing service to the consumers (MV / side service). Supply
interruption of the consumer is attended by the stand by office Staff.
Depending on their availability, the O&M, Construction and DCC can
utilize them for finding Substation location and for collecting informations from
site etc.
1. DOHA STAND BY / EMERGENCY CALL CENTRE
2. KHALIFA TOWN STAND BY
3. RAYYAN STAND BY
4. WAKRAH STAND BY
5. M. SALAL STAND BY
6. KHORE STAND BY
7. AL- GHOWAIRIYA STAND BY
8. SHAHANIYA STAND BY
9. RUWAIS STAND BY
Substation Assistant –SSA
Controlling from NCC / DCC
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programme after obtaining proper data from DCC and send to the DCC
prior to the execution(48 hrs before).
For emergency break down / tripping work the field engineer should
operate according to the proper instruction from control engineer on
duty ( DCC).
Distribution System Protection
IntroductionThe function of a protection scheme is to ensure the maximum continuity of
supply. This is done by detecting the faults and isolating the minimum
possible part of power system during fault and abnormal condition. Protective
relays are the devices that detect abnormal conditions in the Electrical power
system by constantly monitoring and measuring Electrical quantities as wellas various other parameters to discriminate between Normal and abnormal
conditions. The basic Electrical quantities which are monitored for detecting
abnormal conditions are
Voltage
Current
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3) Phase to phase (L-L)
4) Phase to ground (L-G)
5) Phase to Phase with ground (L-L-G)
Faults in system
Cable faults – Joint faults, termination faults and third party damage
Transformer faults – Incipient faults, over loads, terminal faults, winding
faults and through faults
Switch gear faults – Flash over due to insulation failure
Bus bar faults
Natural events
Physical accidents
Mal operation
Kahramaa Distribution system protection
The protection scheme used in Distribution Network including the Primary
substation, Indoor substation and outdoor substation are detailed below.
Primary Substation protection
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It always directed towards transformer LV winding. Protects the transformer
from heavy circulating current occurred at the time of tap changing and it also
protect the other source in the same Bus from the internal LV fault of the
transformer.
6) Temperature, Gas and oil surge protection for transformer
Main TX Bucholz /PRV trip
Tap changer Bucholz surge/gas trip
Earthing TX Bucholz surge trip
Main Transformer winding temp trip
Eathing TZ Bucholz Alarm
Earthing TX low oil level
Main TX Bucholz Alarm
Main TX winding temp alarm
Main TX low oil level
Other Relays
Master trip Relay-All relays are wired to the master trip to initiate the tripping
signal for Circuit breaker. Type –F8H trip relay.
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Used to provide Auxiliary supply to primary substations (415 volts)
Stand by Earth fault Protection
Stand by earth fault relay is provided in the secondary circuit of earthing
transformer neutral CT. If an earth fault is not cleared by appropriate Circuit
breaker of 11KV feeder in the Primary substation, the earth fault current will
continue to flow through of the 66/11KV transformers in the Primary
substation.
If the fault persists without clearing by the feeder earth fault protection the
fault will be cleared by the SBEF stage 1 and 2 timer relays. Stage 1 will trip
the bus section and stage 2 will trip the transformer. Main features are as
follows.
o Protects the 11 KV distribution systems including the Primary
transformer LV winding from Earth fault and the maximum earth fault
clearing time is limited 3 seconds.
o The SBEF relay will initiate “Flag ON” condition for all earth faults
(magnitude higher than the set value). Current setting depends on the
independence of the Earthing transformer.
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11 KV Bus bar Protection
1. Partial Bus bar Protection
2. SBEF where there is no partial bus bar protection and in the substations
with partial bus bar, SBEF act as a back up protection.
Partial Bus bar protection
Partial bus bar deferential protection employed in the 11 KV feeders of
primary substation equipped with bus section breaker. This relay works on
deferential principle and the relay is connected across the secondary CT’s of
bus coupler and incomer with an overlapping arrangement. The feeder CTs
are not involved in this scheme of protection causes relay operation during
through fault condition. To avoid this, discrimination between Bus Bar fault
and 11 KV feeder faults is provided. Main features are as follows.
♦ It protects a portion of Bus Bar from bus Bar faults and provides a back up
protection for the 11 KV feeders. For 11 KV system faults feeder protection
act first and when it fails partial bus bar protection will act as back up.
♦ The phase fault element of the partial Bus Bar protection is graded with the
feeder phase fault protection and Earth fault element is graded with feeder
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send blocking signal, PBDP (50 high set)will trips the LV ,HV side breakers of
transformer along with the Bus coupler breaker.51 elements act as a back up
protection for the feeder
Grading
50element -100 milli sec time delayed operation.
51element (O/C) – graded with the feeder IDMT O/C and TX HV side O/C
(Time grading only possible - 300 milli sec)
51 element (E/F) - graded with feeder E/F (IDMT) and SBEF
(Magnitude grading only possible)
CT is -2000/1; current setting is normally 7% (300 m sec time grading)
Primary substation feeder protection
Normal protection scheme consist of the following relays.
1. Pilot wire protection
2. Standard IDMT Relays (2 O/C +1E/F)
Pilot wire protection
A type of unit protection
Solkor R instantaneous protection (60 milli sec)
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• The padding Resistance to set to a value such that, the total loop
resistance of the pilot wire cable is 1000 Ω. Let RL be the Pilot wire
lead resistance. There the padding resistor to be provided at each end
is , RP =1000-RL Ω (RL is normally about 10 Ω).
• Current Check Relay (B 69 Relay) is used in series with the SOLKOR
Relay and it will prevent the tripping of the 11 KV cable feeder on
account of any pilot wire open condition or pilot wire shorted condition.
For the current check Relay the O/C setting is provided with more than
the O/C setting of the IDMT O/C relay on the feeder.
• Pilot wire supervision relay is also used to detect any fault in the pilot
wire circuit and for any type of fault in the pilot wire
• If pilot wire supervisor Relay or current check relay is not provided
along with SOLOKOR R Relay, the following situations can occur
SOLOKOR R unit protection acted and the Feeder trips only at receiving end,
it can be assumed that it is pilot wire problem and in this Situation, the feeder
not to be put in service until the Pilot wire unit protection is decommissioned.
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100 milli sec –300 milli sec delayed operation is provided for this type relay in
order to avoid tripping during heavy inrush currents (100 m sec –300 m sec) is
the decaying time required for inrush. In some cases, SOTF protection is also
provided with Harmonic Restraint feature (100 millisecond delay ) or with out
Harmonic Restraint feature (300 millisecond delay ). The 2nd Harmonics from
magnetizing inrush currents or switching surges will decay with in 300 milli
second.
51- Normal IDMT element with grading.
Stage-2
50 element - Initiate blocking signal to the Partial Bus bar high set element
and the signal will reach within 60 milli sec. during a fault in the out going
feeder. The High set element of IDMT relay is not used for tripping but it
sending blocking signal to the partial Bus bar relay.
Relay Operation
For Three phase balanced fault – R&B O/C relay will operate.
For Three phase earth fault - R&B O/C relay will operate
Phase to phase fault - R or B phase O/C relay will operate
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LV side winding and cable up to the CT point is protected by Restricted
Earth fault protection. (In case of consumer MV panel with ACB and
REF relay available)
From MV panel REF relay to HV panel, intertrip cable used for the
connection for 11 KV inter tripping.
IDMT relay with EI Characteristic is used. This Provides better grading
with the MV fuses. Type TJM 31 &2TJm31.
Separate High set instantaneous element is provided to protect
transformer from heavy fault
Current setting and CT ratio required is as per the transformer capacity
High set relay setting is as per the short circuit fault current of the
transformer. (To avoid the unwanted tripping due to magnetizing inrush
current, 130% of the expected fault current is taken for relay current
setting)
MV side protection - Fuse protection is available.
- ACB with REF is provided in some consumer panel
Time and Current grading
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1000 KVA - 60A
1600 KVA - 90A
Transformer with SF6 TX switch
Time lag fuses are provided in the CT secondary circuit to protect HV side.
TLF required for Transformers with different CT is shown below.
Voltage
KV
TX Rating
KVA
CT Ratio
A
TLF rating
A
Max.distributor
fuse link rating
A
11 200 50/5 3 160
11 300 50/5 5 250
11 500 50/5 7.5 315
11 800 50/5 12.5 400
11 1000 100/5 7.5 500
11 1250 100/5 10 630
11 1500 100/5 12.5 630
11 1600 100/5 12.5 630
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IN OH/L, the earth path resistivity is very high and then the normal E/F relay
will not detect the earth fault of the system. To overcome, this condition OH/L
are provided with sensitive earth fault relay (current setting is 3% with a long
definite time lag of 3 seconds).
CT Ratio - standards
Primary substation
LV side of TX and Bus bar - 2000/1 for PBDP
-2000/1 for D O/C and D E/F
Out going Feeders - 400/1 or 300/1 for IDMT, SOLOKER R & Metering
Earthing Transformer - 750/1 (Neutral CT)
Indoor substation
Feeders - 300/5 or 400/5 for SOLKER R, IDMT and
metering.
Transformers - 150/100/50/5, 80/40/5, 60/30/5, 100/50/5
for IDMT & Metering
Out door substation
Transformer with SF6 TX Switch – 100/5 or 50/5
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• Circuit Breakers – Method of isolation.
• Pot End & Cap End Cables.
Operational & Safety Locks with Keys.
For better operational and system safety, kahramaa provided Operational and
Safety locks with keys to their Field engineers. Apart from operational & safety
lock, Substation keys are also available and is provided to all field engineers
and to some contractors.
Operational lock with key
Indoor and Outdoor Substations
All Switches, Circuit Breakers, Panels, Isolating and Earthing devices are
provided with Operational lock with key. Normally two types available and
given to all Field Engineers.
1) 246 Type
2) Den ( Department of electricity network )- small size
Strictly follow kahramaa’s Safety Rules, while using the operational locks
during the work.
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where the circuit on which work is to be carried out could be energized. The
keys for such locks shall be kept in a key safe, if provided, or in some other
safe place preferably in the possession of the Senior Authorized Person in
charge of the work. See Kahramaa Safety Rules12.3
Locking facility available for Indoor VCB
• Bus Bar spout shutter
• Feeder spout shutter
• Earth Switches
• Push Button ( Trip / Close )
• Panel Door
Interlocking features available
• Without opening the OCB, the inter locking lever will not be
disengaged.
• The Isolating lever entry is possible only when the OCB/VCB in opened
condition.
• Closing of Earth Switch is allowed only when the VCB is in Racked
Out/Test position.
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A data transfer is provided to transfer the operation status of CO2 spraying
system (Automatic / blocked / manual) to NCC and it will gives alarm for the
changes in operation. So the field engineer should inform NCC before doing
any operation.
Confirm Supply
Out Door Substation
Check the humming sound of Local Transformer.
Check the vibration of transformer.
Ammeter Indication from MV panel / Feeder pillar.
Indoor Substation
Check Transformer humming sound & vibration.
Check Meters indication in the switchgear panel
Check Station Battery charger voltage.
Station lighting
Location Map
An up to date location route map is provided to all Field Engineers for helping
them to find out the Location of Substation.
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identification failed and then close the main switch one by one. Then
identify the circuit from the feeding source by checking the station
supply.)
Pot End & Cap End Cables
Pot End ( P.E ) - Idly charged cable without connected load.
One ends of the cable is connected to the 11KV Bus and the other end is kept
free ( not terminated but the terminals are made and covered with a pot
termination kit ). Pot End cable is idly charged from one end.
Cap end ( C.E ) - Earthed Cable
One end of the cable is connected to the 11 KV Bus and the other end is kept
free, not terminated but only covered with a cap. The cap End cable is always
in earthed condition from its 11 KV Bus side.
Parallel Operation
Condition for parallel operation of two systems
1. frequency,
2. Voltage and
3. Phase sequence should be same
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The power transfer from a source to load is always depends on
the total impedance (transformer + line + generator) and the voltage angle /
load angle of the system. Here Reactive power transfer is always depends on
the magnitude of the voltage, that is always higher voltage to low voltage. The
active power transfer is always depending on the load angle / voltage angle
’’δ’’ irrespective of the magnitude of the voltage. So magnitude of the voltage
is depends on the voltage regulation and in turn depends on the impedance of
the system. Therefore the percentage impedance and voltage phase angle /
load angle are the determining factors of load flow from a source to a load at
remote end. The following factors determine the power transfer and thus the
current through a line.
1. Percentage impedance of transformers
2. Impedance of the line up to the load.
3. Load angle at different load centre or the phasor
displacement of voltage between source end and load end.
Bad paralleling
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paralleling. Otherwise, the voltage difference cause to produce high circulating
current and this trips the weaker portion.
One another reason for tap blocking is the tap changer is designed to
operate on load condition and not for operating on fault condition. One reason
for blocking the tap during paralleling is to avoid flow of fault current through
the tap changer while tap changing takes place.
Isolation and Earthing for Different Switchgears
Oil Circuit Breaker - Vertical isolation.
1. Service position - OCB, connect the Bus bar to the feeder /
transformer circuit when OCB is in closed condition , the live Bus bar is
connected with the feeder / Transformer.
2. Circuit Earth Position ( CK/E )
OCB provides connection facility between feeder / transformer circuit and
earthing system (station earth) .When OCB is in closed condition , the feeder /
transformer circuit is in earthed condition.
3. Bus bar Earth Position
OCB provides connection facility between Bus bar and earthing system. When
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TAMCO VCB
1 L/TX – 1000 KVA
4345 – I/D –OCB
9899 I/D – VCB.
termination for the new s/s. After
the work cancelled t he PTW. SFT
issued to HV / pressure test for the
cable between the I/D including
new s/s. P/ Test done at new I/D.
and cancelled SFT& confirmed
SW/ position. Live phasing done at
new s/s (11325- I/D).
Commissioned new s/s and local
TX.
05-06-2006
Eng. Dharam
Commissioning of new O/D
substation, Semi extensible 12603
with 1250 KVA transformer,
LABOUR CAMP –O/D in between
9935 I/D and 3828 O/D substation.
RMU is TAMCO ( SF 6 )
After proper back feeding, the
working portion isolated and
earthed as per switching
programme. Issued SFT to
identify, spike and color phasing
the cable. Cancel SFT & confirm
SW/P. Issued PTW to break and
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A400 is Connecting to the 10811
SALWA RD SHML I/D ( VCB – EPE
make )
confirm SW/P. Issued PTW to
make one No. ST. joint for the
cable A400 between the two I/D’s
after the work cancelled PTW.
Issued SFT for P/T and cancelled
SFT confirm SW/ P. After checking
11 KV live phasing, cable A400
commissioned.
07-06-2006
Eng Nizamudeen
Commissioning of 10132 KSW- I/D
in between 4180 (O/ D) and 4160
(O/D) substation.
Commissioned the new I/D and one
local TX (1000 KVA) commissioned
after checking the existing MV
Shifted the load as per switching
programme. Isolated & Earthed the
working section at both end.
Issued SFT for identification, spike
and colour phasing. Cancelled
SFT & confirmed SW/ position.
Issued PTW for 2 Nos. straight
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Extendible type
Commissioned new RMU with an
additional feeder switch.
PTW. Issued SFT , cancelled SFT
& confirm SW/P.11 KV Live
phasing done at 5167 DN- 13 I/D.
13-06-2006
Eng. Nizamudeen
Replacement of Defective RMU at
10313 KR – 6 O/D and to close the
ring with spare cables of 10313 KR-
6 O/D between 9787 KHORE EAST
-5 and 10319 KHORE SOUTH O/D
After MV check and phase rotation
commissioned the s/s and TX’s.
After isolation, applied CME at
both ends. SFT issued for colour
phasing. cancelled SFT , PTW
issued to make 3 Nos ( Break and
make ) termination at 10313 O/D
and for I No. Termination at 9787
O/D and also for one ST joint
between 10319 KR-9 O/D and
120313 O/D. Cancelled the PTW.
Issued SFT for HV P/Test,
Cancelled SFT& confirmed the
SW/ P. Live phasing done at
10320 I/D
14-06-2006 11 KV cable diversion between After load shifting and isolation,
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Progress report on Distribution Protection
18.06.2006
Eng. Shahul
Location- 11456 Villagio -11 I/D
ABB Make numerical relay
Replacement of SPAJ135C by
new high set SPAJ140C for L/TX’s
19.06.2006
With technicians
Pre commissioning test for I/D Attended magnetization test,
Primary injection, Trip circuit
healthy test for breakers
20.06.2006
Eng. Shahul
1.Abu Hamur North PRY
SIEMENS-SIPROTEC-7SJ61
2.Indoor substations
After fault maintenance- Setting
change for feeders
Relay setting change- as per DCC
advice
21.06.2006
With technician
1671- O/D- Industrial area
Old L/TX is 500 KVA
Setting change for L/TX (1000
KVA)
CT Ratio changing
22.06.2006
With technician
Saliya PRY A200 Tripped, Solkor
operated
Solkor decommissioning attended
25-05.2006 to
28.06.2006
NCC Attended routine activities
01.07.2006 Transmission protection Commissioning
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Progress report (O &M)
Date Engineer Work Remark Safety
22-05-06 Mr. HAKKIM
Mr. Raju
Replacement of faulty TX4 (Due to oil leak )at
(9649) City Centre -1-1/D
VCB – TAMCO
1.Replacement of faully TX (Due to oil leak)atan O/D substation.
2.Replacement of transformer(BOFP) by aNew TX ( FSFP) at an O/D substation.
VCB – TAMCO
E/S – available for eachcircuit consumer MV panelwith ACB available and REFrealy provided for MV sideprotection.Inter trip for HT isprovided.Before restoringMV side,Checked MVvoltage & Phase rotation
O/D extensible RMU ( oil )Yorkshire type.
Semi Extensible RMU ( Oil).Before restoring MV sidechecked MV voltage &phase rotation.
Operational safety as per
switching programmeinstruction from systemcontrol engineer.
After proper isolation &Earth, issued PTW for Break and make 11 KVtermination.
Operational safety as per SW/ProgrammePTW issued for breakand make HTtermination to New TX.Operational safety as per SW/ProgrammePTW issued for breakand make HTtermination to New TX.
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Date Engineer Work Remark Safety
23.05.06
24.05.06
25.05.06
Mr.Rajivkumar
Mr. Hakim
Mr. Raju(Stand by Duty)
NOP shifting programme toLoad DUHAIL PRYsystem operation duty.
1) Rectification of faulty cable by makingstraight joint& charging the cable.(Cable bitween 1036 city BANK s/s I/Dand 5716 O/D )
2)Rectification of faulty cable between (2462 ) SH EID BIN MAD No: 3 s/s andan O/D S/S
Fault restorationSFT & PTW issued for an HT Cablebetween NDC,PRY & an I/D S/S
3nos1/D&5nosO/D Substation visited as apart of NOP shifting.
VCB - EPE, TAMCOOCB - south walesRMU -
Tiger oil switchVCB – AGEStraight jiont fault
Third party damage
NDC, PRY visitedOCB Panel,Co2 Blasters provided for safety
Operation as per systemcontrol ( DCC )switchihng programme.Confirm supply isimportant in each
operation.
Issue SFT for Identification, Spike&Colour phasing .Issue PTW for onetermination & one No:ST joint nearer to 5716O/DIssue SFT for
spike,colour phasing the
cable.Issue PTW for straight
joint the cable
SFT issued for Identification,Spike&Colour phasing. IssuedPTW for 2 Nos stright
joint.
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27.05.06 Mr. Raju Transformer replacement ( BOFP ) -1000KVABy new one at 725 I/D
Ray Rolle OCBMV Voltage & Phase rotation checkedbefore MV restoration
PTW issued for Break &make 1 No.HTtermination to loop thetransformer
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28.05.06
29.05.06
30.05.06
31.05.06
Mr. Mahmood
Mr. Inose
Mr.Rajivkumar
Mr. Hakkim
11 KV OHL – Maintenance-Redial circuit from ( 9757 ) new Al QayanO/D ( Al Khore lnd.Area)Replacing ABS (S-144 ) , (S- 145) & 8Nos. LA installation at Pole box and PMT
Cable fault Rectification
1.Replacemant of faulty O/D substation(package type) at 4362 O/D – HV P/Testpending
2. SF6 gas pressure Low -Refilling at5484 O/D Substation ( Lucy SF6 )
1.Fault rectification of an HT cablebetween SH . ABDULLA FARM-1 1/Dand pole BoxPole Box termination faulty.
RMU at O/D s/s isSF6 ( TAMCO )
Ray Roll OCB
HV Pressure Test done for new O/Dsubstation.Live phasing done at 2569 1/D. Before the
Live phsing Existing and new phaserotation checked at 2420 O/D.
Checked 11 KV line phasing at 1/D
Over head line involved
transformer.
After isolation &Earthissued PTW to thecompetent person( Before issueing PTW,test OHL,if Dead,Apply
Portable Earth )
Issued SFT for colour phasing the HT cableIssued PTW for making2 No Stright joint for thefaulty cable.
Issued SFT for HVP/Test for the new O/D
subatation.Issued PTW for refillingSF6 Gas at 5484 O/Dsubstation.Issued PTW for MVtermination.
Issued SFT for colour phasing thecable.Tested the OHL,found Dead then appliedthe protableEarth.Issued PTW for
722 Fault restoration 1/D – E/F relay operated
one No. Jumper connection and for raisethe Pole box.Noticed all indication
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01.06.06
2.Fault restorationKHORE A300- tripped at an 1/Dsubstation, the OHL lodial line ( with twoTEE off -circuit ) Total supply failure.Indication - stand by E/F flag ON at PRYand alarm initiated at NCC for both TX
ABU HAMUR WORK SHOP VISIT
2) Fault restorationIndustrial area 1671- MI 1/D
Substation, one TX ( 500KVA ) tripped
on over loadTX -replaced by ( 1000 KV )
1/D E/F relay operatedEFI flagged at one pole Box(Radial TEE-off circuit )
Hands on training on different types of switches ( Oil & SF6 ), VCB & OCB’S
Indication R&B O/C
Noticed all indicationand after proper petrolling found that theearth wire(1 span)snapped in the radialTEE-off circuit.Isolated &earthed the faultyportion. Then charged
the healthy circuit fromthe 1/ D (All Relays andindications resetted.Keptthe relay setting TSMminimum for testcharging.).PTW issuedfor fault rectification.Issued PTWfor transformer replacement.Informedprotection department to
change the relaysettings.