specifications of hv switchgear

8/12/2019 specifications of HV Switchgear

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POWERING TAMIL NADUS PROGRESS

Specification No: ACE/GTS/OT-72/07-08Volume-III Technical Specification-Electrical

500 MW MTPS STAGE-III VOL-III/E12/R0

SPECIFICATION E12

HT SWITCHGEAR

CONTENTS

CLAUSE NO. DESCRIPTION PAGE NO.

1.00.00 General 1

2.00.00 Major Components 1

3.00.00 Description 14.00.00 Design Criteria 2

5.00.00 Specific Requirement 3

6.00.00 Tests 15

7.00.00 List Of Drawings And Documents To Be Submitted With Bid 15

ATTACHMENTS

ANNEXURE-A Ratings and Requirements 17

ANNEXURE-B Protection 20

ANNEXURE-C Bus Transfer Scheme 23


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SPECIFICATION E12

HT SWITCHGEAR

1.00.00 GENERAL

The AC Power Supply-Medium Voltage (11kV and 3.3KV) System suppliespower to plant auxiliaries requiring power on the 11kV and 3.3KV system andincludes necessary fault detection & protection devices and annunciation inswitchgear.

2.00.00 MAJOR COMPONENTS

The AC Power Supply-Medium Voltage (11kV and 3.3KV) System shall consistof the following components: -

11kV and 3.3KV switchgears

Segregated phase bus duct.

Unit/Standby transformer

Unit/Station Auxiliary Transformer

Neutral Grounding Resistor

Raceways, conduits, conductors and conductor accessories

This section covers the details on 11KV and 3.3 KV Switchgears

The switchgear shall be complete with Autobus transfer panel and base channel

frame with hardware.

3.00.00 DESCRIPTION

The generation voltage of 21kV will be connected to 400KV system viarespective step-up generator transformer. The medium voltage 11 kV systemwill derive power from two generator bus ducts through respective 21/11kV UnitTransformers and one 230/11 kV Standby Transformer.

The two winding unit transformers receive power from their respective gen-erators through the isolated phase bus duct and feed 11kV power to UnitSwitchgears from secondary.

One no. 230/11 KV, 2 winding Standby Transformers will be fed from 230kVindoor GIS switchyard.

This power is transformed to a nominal system voltage of 11kV and delivered tothe 11kV station switchgears through segregated phase bus ducts.11KV powerwill be further stepped down to 3.3KV and 415V for feeding motors and otherloads. The 11/3.3KV switchgear distributes power through feeder breakers tothe 11/3.3 KV auxiliary loads.


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The AC Power Supply-Medium Voltage (11/3.3KV) System has the followingfeatures for redundancy, diversity, and separation of the system:-

a) Each switchgear has both a main and reserve power supply feed. Eachswitchgear will have a high-speed Numerical based on-load bus transferscheme with momentary paralleling facility.

b) Breaker control, alarms, and monitoring of the AC Power Supply-MediumVoltage (11/3.3KV) System shall be provided at the main control room fromEDMS / DDCMIS monitors. .

c) The normal on-line operating conditions of the AC Power Supply-MediumVoltage (11/3.3KV) System allow for the unit auxiliary transformers to providepower to the auxiliary loads. The normal off-line operating conditions of the AC

Power Supply-Medium Voltage (11/3.3KV) System allow for the station auxiliarytransformer to provide power to the auxiliary loads. In case of unit failure, powersupply to 11kV Unit Board will have Fast-bus changeover to station source. Inaddition, all 11kV & 3.3kV boards will have facilities for synchronized plannedmanual/auto changeover.

4.00.00 DESIGN CRITERIA

4.01.00 The switchgear shall be used to supply power to 11kV and 3.3KV motors andother loads for various plants.

4.01.01 Duty involves direct-on-line starting of large induction motors and also undercertain emergency conditions transfer of loads from normal to stand-bysource of supply.

The motor starting current varies from 6 to 8 times the full-load current, with amaximum of 3 starts per hour.

4.01.02 The switchgear shall be located in a clean but hot, humid and tropicalatmosphere. The switchgear room shall be provided with necessary airblowing arrangement.

4.01.03 Switchgear ratings and requirements are detailed in the enclosedANNEXURE-A. Equipment shall be furnished in strict accordance with thesame.

4.01.04 For continuous operation at specified ratings, temperature rise of the various

switchgear components shall be limited to the permissible values stipulated inthe relevant standards and/or this specification.

4.01.05 The Switchgear and components thereof shall be capable of withstanding themechanical forces and thermal stresses of the short circuit current listed inthe annexure without any damage or deterioration of material.


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4.01.05 Circuit breaker shall not produce any harmful over-voltage during switchingoff induction motors. The surge protective devices of suitable rating asrequired shall be included in the scope of supply to limit over-voltage.

4.01.01 The switchgear shall be suitable for extension on both sides.

4.01.01 11 KV & 3.3 KV Switchgear for CHP and AHP.

The motor feeders shall be provided with SF6 circuit breakers /Vacuumcontactors. The motor feeders below 600KW with rated current of 400 A,draw out type vacuum contactors shall be provided with a backup HRC fusesfor short circuit protection.

5.00.00 SPECIFIC REQUIREMENT

5.01.00 Construction

5.01.01 The switchgear shall be indoor, metal-clad, floor mounted, draw out type.Design and construction shall be such as to allow extension at either end.

5.01.02 The switchgear enclosure shall conform to the degree of protection IP-5X.The minimum thickness of sheet steel used shall be 2 mm.

5.01.03 The switchgear assembly shall comprise a continuous, dead-front, line-up offree standing, vertical cubicles. Each cubicle shall have a front-hinged doorwith latches and a removable back cover. All covers and doors shall beprovided with neoprene gaskets.

5.01.04 Switchgear cubicle shall be so sized as to permit closing of the front access

door when the breaker is pulled out to TEST position. The working zone shallbe restricted within 750 mm to 1800 mm from floor level.

5.01.05 Circuit breakers, instrument transformers, bus bars, cable compartment etc.,shall be housed in separate compartments within the cubicle. The designshall be such that failure of one equipment shall not affect the adjacent units.

5.01.06 All relays, meters, switches and lamps shall be flush mounted on therespective cubicle door or on control cabinet built on the front of the cubicle.

5.01.07 Dummy panel shall be provided in the switchgear line up, if required, for easytermination access of power and control cables.

5.01.08 The motor space heaters shall be controlled from separate module in MCCwith necessary interlocks with switchgear.

5.01.09 The wiring for space heaters of Switchgear compartments shall besegregated from the control wiring.

5.01.10 In each of the 11KV and 3.3 KV switchgear one spare feeder for each typeshall be provided


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5.01.11 Each cubicle shall be provided with 230 V AC lamp controlled by limitswitches for illumination in the cubicle chamber while opening cubicles for

maintenance purpose.

5.02.00 Bus and Bus Taps

5.02.01 The main buses and connections shall be of high conductivity copper/aluminum alloy, sized for specified current ratings with maximum temperaturelimited to:

a. For bolted joints (Plain or tinned) : 90oC (i.e.40oC rise over 50oCambient)

b. For bolted joints (Silver plated) : 105oC (i.e.55oC rise over 50oCambient)

Bus bar temperature rise shall be limited to 35oC even while the ambient is50oC.

Copper bus bars shall be used for bus bar current rating above 2000A.

5.02.02 All bus connections shall be silver plated. Adequate contact pressure shall beensured by means of two bolts connection with plain and spring washers andlocknuts.

Bimetallic connectors shall be furnished for connections between dissimilarmetals.

5.02.03 Bus bars and connection shall be fully insulated for working voltage with

adequate phase/ground clearances. Insulating sleeves for bus bars and cast-resin shrouds for joints shall be provided.

Bus insulator shall be flame-retardant, track resistant type with high creepagesurface.

5.02.04 All buses and connections shall be supported and braced to withstandstresses due to maximum short circuit current and also to take care of anythermal expansion.

5.02.05 Bus bars shall be color coded for easy identification and so located that thesequence R-Y-B shall be from left to right, top to bottom or front to rear, whenviewed from front of the switch-gear assembly.

5.03.00 Circuit Breaker

5.03.01 Circuit breaker shall be triple pole, single throw Sulphur hexafluoride (SF6)power circuit breaker elements.

The Sulphur hexafluoride (SF6) breaker shall be provided with proper deviceto monitor the gas pressure in the interrupting chamber shall be provided. Thedevice shall initiate a group alarm on DDCMIS and indication on affected


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breaker panel. In case of loss of pressure to atmospheric pressure, the failedbreaker shall be able to break rated load current.

SF6 gas cylinder with all filling devices required for site filling shall also beprovided.

5.03.02 Circuit breakers shall be horizontal draw out type, having SERVICE, TESTand DISONNECTED positions with positive indication for each position.

5.03.03 Circuit breakers of identical rating shall be physically and electricallyinterchangeable.

5.03.04 Circuit breaker shall have motor wound spring charged trip free mechanismwith anti pumping-feature and shunt trip. In addition facility for manualcharging of spring shall be provided.

5.03.05 For motor wound mechanism, spring charging shall take place automaticallyafter each breaker closing operation. One open-close-open operation of thecircuit breaker shall be possible after failure of power supply to the motor.

5.03.06 Mechanical safety interlock shall be provided to prevent :

a. The circuit breaker from being racked in or out of the service positionwhen the breaker is closed.

b. Racking in the circuit breaker unless the control plug is fully engaged.

5.03.07 Automatic safety shutters shall be provided to fully cover the female primarydisconnects when the breaker is withdrawn.

5.03.08 Each breaker shall be provided with an emergency manual trip, mechanicalON-OFF, indication, an operation counter and mechanism charge/dischargeindicator.

5.03.09 Each breaker shall be provided with following:

a. Auxiliary switch, with 6 NO +6 NC contacts, mounted on the draw outportion of the switchgear.

b. Position/cell switch with 4 NO +2 NC contacts, one each for TESTand SERVICE position.

c. Auxiliary switch, with 8 NO + 8 NC contacts, mounted on thestationary portion of the switchgear and operated mechanically by asliding lever from the breaker in SERVICE position.

Alternatively electrically reset type latching relay may be used for thepurpose.

5.03.10 Switch contact shall be rated 10 A AC. and 2A DC at their respectiveoperating voltage.


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5.03.11 Limit switches shall be convertible type.

5.04.00 Control & Indication

The circuit breaker shall be provided with Local/ Remote selector switch,wired up for local & remote operation.

Each breaker cubicle shall be equipped with following: -

5.04.01 For motor feeders one (1) TEST-NORMAL-TRIAL selector switch stay puttype with pistol grip handle and key interlock.

5.04.02 Two (2) heavy-duty oil tight, push buttons for TRIP & CLOSE.

5.04.03 ALARMS / INDICATIONS / SER POINTS

Control room alarms and indications

The following indications / alarms are the minimum to be provided in theDCS/EDMS TFT in the control room. Additional indications / alarmsconsidered necessary during the detailed engineering stage shall also beprovided.

Out of these, some shall be selected for the sequential events recording.Foreach feeder, grouped alarm for any abnormal condition of that feeder shall beprovided on the control panels. The control / interlock schemes for varioustypes of feeders shall be commensurate with their application.

(a) Common for each breaker panel

(i) Status Indication

Breaker onBreaker off

Breaker in remote

Breaker in serviceBreaker in testCircuit side earthed

Bus side earthed (as applicable)Spring charger indication

Local/Remote

(ii) Alarms

L/O Relay operated

SF6 gas pressure low (in case of SF6 CB)Trip circuit unhealthy


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(b) Incomers from unit auxiliary / Standby transformer

Sources paralleled beyond preset time

Outgoing breaker trip

c) VT Panels

Bus under voltage

L/O relay operatedBus PT fuse failedDC supply 1 failed.

DC supply 2 failed

Bus PT not in service

d) Motor Feeders

Overload alarm

e) Service Transformer Feeders

Oil temp Hi alarm

Oil level low alarm

Winding temperature Hi alarm

Buchholz relay alarm

f) Tie Feeders

Sources paralleled beyond preset time.

g) Analog Parameters

All the parameters, for which the transducers are provided, shall bedisplayed in the DCS/EDMS CRTs in the control room.

h) Control

ON / OFF control and ON / OFF & fault / discrepancy indication for each ofthe breakers shall be provided in the CRTs. Control panel in the controlroom shall be provided with control of all synchronizing breakers i.e.,incomers and tie breakers with auto-off-manual switches.

i) Indication Lights on the Switchgear compartments

Seven (7) indicating lights on front of compartments: -

GREEN : Breaker Open

BLUE : Spring Charged

RED : Breaker Closed


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AMBER : Trip

ORANGE : Gas Pressure Low ( for SF6)

YELLOW : Lock out relay healthy

WHITE : Trip Circuit healthy

5.04.04 Lamps shall be front loading clustered type LED module pilot lights inthermoplastic enclosure with polycarbonate lens and diffuser. LED shall beprotected by in-built fuse with surge suppressor and leakage voltage glowprotection. Lamp and lens shall be replaceable from front. LEDs used forindication shall have pick up and drop out voltage within -20% of the operatingvoltage.

5.04.05 The commands from DCS shall be wired to the breakers through interposingrelays to be mounted in the switchgear.

5.04.06 The scheme of protection shall be as per ANNEXURE-B attached. Biddershall develop and furnish the wiring and control scheme accordingly.

5.05.00 Current Transformer

5.05.01 Current transformers shall be cast resin type. All secondary connections shallbe brought out to terminal blocks where wye or delta connection shall bemade.

5.05.02 Accuracy class of the Current Transformers shall be: -

a. Class PS for differential relaying (or as required depending on the typeof relay selected).

b. Class 5P20 for other relaying.

c. Class 0.5 and ISF


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the top of cubicle is not acceptable. Voltage transformer shall be mounted in aseparate panel.

5.06.02 High voltage windings of voltage transformer shall be protected by currentlimiting fuses. The voltage transformer and fuses shall be completelydisconnected and visibly grounded in fully draw-out position.

5.06.03 Low voltage fuses shall be sized to prevent overload and shall be installed inall ungrounded secondary leads. Fuses shall be suitably located to permiteasy replacement while the switchgear is energized.

5.07.00 Relays

5.07.01 Relays shall be of draw out design with built-in testing facilities and flushmounted at the front of panel. Small auxiliary relays may be in non-draw outexecution and mounted within the cubicle.

5.07.02 Relays shall be rated for operation on 110V secondary voltage and 1 or 5 Asecondary current. Number and rating of relay contacts shall suit the jobrequirements.

5.07.03 Unless mentioned otherwise in the specification, protective relays shall bemultifunction type numerical relays of latest version to be approved by owner.

5.07.04 Multifunction numerical relays shall be selected to provide an integratedprotection measurement and monitoring functions. Features such as self-diagnosis, Watch dog provision for relay healthiness, facility for differentgroup of setting, disturbance recording, sequence of event recording and timestampings shall be available with the relay. All data shall be stored in non-volatile memory backed up by battery. The relay shall have front LCD displayand menus, fixed function and programmable LEDs, programmable I/Os,keypad etc and they shall be password protected. Communication port forlocal and remote (with suitable protocol) communication shall be located inthe front and rear part of the relay for communication with EDMS/DDCMIS.

A laptop loaded with support software shall be provided for local off lineprogramming, measurements, exftracting and viewing of events, disturbanceetc.

The relay shall be housed in dust tight enclosure, suitable for IP 52 degree ofprotection.

5.07.05 The Contractor shall furnish, install & co-ordinate all relays to suit the

requirements of protection, interlock and bus transfer schemes as broadlyindicated in ANNEXURE-C.

5.08.00 Meter

5.08.01 Indicating instruments (96 x 96 mm) shall be Taut- band type, with 240-degree scale, anti-glare glass and accuracy class of 0.5% full scale. Eachmeter shall have zero adjuster on the front.


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5.08.02 Motor ammeter shall have extended suppressed end-scale range to indicate

starting current (6-8 times full load).

5.08.03 Energy meter shall be three phase multifunction, digital type withcommunication port for EDMS/DDCMIS interface. The energy meter shall belocated in respective switchgear cubicle of all incomers and outgoing feedersexcept motor feeders. For motor feeders the energy data shall be generatedin DDCMIS.

5.09.00 Transducer

Transducers shall be provided for conversion of AC electrical quantities suchas voltage, current and power. Transducers shall be of low burden typehaving 4 20 mA DC linear galvanically isolated output compatible withsecondary indicating instrument. Transducer shall be dual channel type (slim

model, latest version).

The transducer shall be mounted in separate transducer panel, which shall belocated in UCP area. The transducer panel shall be powered from 240V ACUPS supply and transducers shall be suitable for this UPS supply.

5.10.00 Switch

5.10.01 Switches shall be dust protected, heavy duty, switchboard type complete withescutcheon plate. Contacts shall be silver surfaced, rated 10A at operatingvoltage.

5.10.02 Lockable stay-put type switchgear / field / remote selector switch shall beprovided as per requirement and mounted on switchgear cubicle.

5.10.03 Meter selector switches shall be maintained contact, stay put type with knobhandle. Ammeter& voltmeter selector switches shall be four position type.Ammeter selector switches shall have make before break feature to preventopen circuiting of CT secondary.

5.10.04 Breaker control switch shall be multistage, spring return to normal, with lostmotion device and pistol grip handle.

5.11.00 Fuse

5.11.01 Fuses shall be HRC, link type, with minimum interrupting capacity equal tothe listed short circuit current. Fuses shall be furnished complete with fuse

bases and fittings. Visible indication shall be provided on blowing of the fuse.

5.12.00 Push Button

Push button shall be heavy duty, shrouded, push to actuate type with coloredbutton and inscription plate. Each push button shall have 2 NO + 2 NC


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contacts, rated 10A and 0.5A at their respective AC and DC operatingvoltage.

5.13.00 Secondary Wiring

5.13.01 The switchgear shall be fully wired at the factory to ensure proper functioningof control, protection, transfer and interlocking schemes.

5.13.02 Fuse, links shall be provided to permit individual circuit isolation from buswires without disturbing other circuits. All spare contacts of relays, switchesand other devices shall be wired upto terminal blocks.

5.13.03 Wiring shall be done with flexible, 1100 V grade, FRLS insulated switchboardwires with stranded copper conductors of 2.5 mm2 for control and currentcircuits and 1.5 mm2for voltage circuits.

5.13.04 Each wire shall be identified, at both ends, with permanent markers bearingwire numbers as per Contractor's Wiring Diagrams. AC / DC wiring shall haveseparate color coding.

5.13.05 Wire termination shall be made with crimping type connectors with insulatingsleeves. Wires shall not be spliced between terminals.

5.13.06 All spare contacts of relays, timers, auxiliary switches shall be wired up to theterminal block.

5.14.00 Terminal Block

5.14.01 650V grade, multi way terminal block complete with mounting channel,

binding screws and washers for wire connections and marking strip for circuitidentification shall be provided for terminating the panel wiring. Terminalsshall be stud type, suitable for terminating 2 nos. 2.5 mm2stranded copperconductor and provided with acrylic insulating cover. Terminals for C.T.secondary leads shall have provision for shorting and grounding.

5.14.02 Not more than two wires shall be connected to any terminal. Spare terminalsequal in number to 20% active terminals shall be furnished. Separate terminalblocks shall be used for AC/ DC wiring termination.

5.14.03 Terminal blocks shall be located to allow easy access. Wiring shall be soarranged that individual wires of an external cable can

be connected to consecutive terminals. Wherever fuse terminal block is usedit must be with LED indications.

5.14.04 Terminal blocks used for interface with DDCMIS via termination cabinet shallbe suitably sized to facilitate proper termination of interconnecting cables.

5.15.00 Cable Termination

5.15.01 Switchgear shall be designed for cable entry from bottom. Sufficient spaceshall be provided for ease of termination and connection.


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5.15.02 All provisions and accessories shall be furnished for termination and

connection of cables, including removable gland plates, cables supports,crimp type tinned copper/ aluminum lugs, double compression brass glandswith tapered washer (Power cables only) and terminal blocks.

5.15.03 Gland plates shall be minimum 3 mm thick. The gland plate and supportingarrangement for 1/C power cables shall be of aluminum.

5.15.04 Sufficient space shall be provided between the power cable termination (end-boxes) and gland plate. Core balance CTs wherever specified, shall beaccommodated within this space.

5.16.00 Bus Duct Connection

5.16.01 Bus duct connections, when specified on ANNEXURE-A, shall be furnished

along with transition panel if required. Unless mentioned otherwise bus ductconnections shall generally be from the top.

5.16.02 All connecting bus work shall have the same continuous rating as associatedswitchgear bus and shall be fully braced for the listed short circuit current.

5.16.03 All provisions such as matching flange and other accessories shall befurnished for connection to bus duct supplied by other. Necessary details forthis purpose shall be furnished later.

5.17.00 Ground Bus

5.17.01 A ground bus, rated to carry maximum fault current, shall extend full length of

the switchgear.

5.17.02 The ground bus shall be provided with two-bolt drilling with Cadmium coatedbolts and nuts at each end to receive 50 X 6 mm Cu. flat.

5.17.03 Each stationary unit shall be connected directly to the ground bus. The frameof each circuit breaker and draw out VT unit shall be grounded through heavymultiple contacts at all times except when the primary disconnecting devicesare separated by a safe distance.

5.17.04 Wherever the schematic diagrams indicate a definite ground at theswitchgear, a single wire for each circuit thus grounded shall be runindependently to the ground bus and connected there to.

5.17.05 CT and VT secondary neutrals shall be earthed through removable links sothat earth of one circuit may be removed without disturbing other.

5.18.00 Earthing Truck

Earthing trucks shall be suitable for earthing the switchgear bus bars oroutgoing cables. The trucks shall have a voltage transformer and an interlockto prevent earthing of any live connection. The trucks shall have audio-visual


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annunciation to warn the operator against earthing of live connections. It shallnot be possible to use bus-earthing truck for cable earthing & vice versa.Earthing truck shall be non- fault making type.

5.19.00 Nameplate

5.19.01 Nameplates of approved design shall be furnished at each cubicle and ateach instruments & device mounted on or inside the cubicle.

5.19.02 The material shall be lamicoid or approved equal, 3 mm thick with white letteron black back ground.

5.19.03 The nameplate shall be held by self-tapping screws. Nameplate size shall beminimum 20 x 75mm for instrument/device and 40 x 150mm for panels.

5.19.04 Caution notice on suitable metal plate shall be affixed at the back of each

vertical panel.

5.20.00 Space heaters and Plug socket

5.20.01 Each cubicle shall be provided with thermostat controlled space heaters and5A, 3 pin plug socket.

5.20.02 In addition, motor feeder cubicle shall be wired-up for feeding the motorspace heater through suitable rated breaker auxiliary NC contact and/orcontactor.

5.20.03 Cubicle heater, Motor heater, Plug/socket circuits shall have individual switchfuse units.

5.21.00 A.C/D.C Power Supply

5.21.01 The following power supplies shall be made available to each switchgear:

A.C. supply : Double Feeder

D.C. supply : Double Feeder

5.21.02 Isolating switch fuse units shall be provided at each switchgear for theincoming supplies, 4-pole, single throw for A.C. and 2-pole, double throw forD.C.

5.21.03 Bus-wires of adequate capacity shall be provided to distribute the incomingsupplies to different cubicles. Isolating switch fuse units shall be provided ateach cubicle for A.C/D.C. supplies.

5.21.04 A.C. load shall be so distributed as to present a balance loading on three-phase supply system.


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5.22.00 Tropical Protection

5.22.01 All equipment, accessories and wiring shall have fungus protection, involvingspecial treatment of insulation and metal against fungus, insects & corrosion.

5.22.02 Screens of corrosion resistant material shall be furnished on all ventilatinglouvers to prevent the entrance of insects.

5.23.00 Painting

5.23.01 All surfaces shall be sand blasted, pickled and grounded as required toproduce a smooth, clean surface free of scale, grease and rust.

5.23.02 After cleaning, the surfaces shall be given a phosphate coating followed by 2coats of high quality primer and stoved after each coat.

5.23.03 The switchgear shall be finished in Siemens grade 631 of IS 5 with two coatsof synthetic enamel paint, unless other wise stated.

5.23.04 Sufficient quantity of touch-up paint shall be furnished for application at site.

5.24.00 Auto Bus Transfer (ABT) panel

An automatic 32 bit or higher micro processor based real time operated fastbacked up by slow transfer scheme shall be provided for change overbetween unit to station source. All hardwires pertaining to above transfersshall be mounted in Auto Bus transfer (ABT) panel. The bus transfer moduleshall have features such as graphical user interface, virtual test simulation,object oriented programming, on line viewing, sequence of event logging, self

diagnostic features and communication port for remote communication. TheABT panel shall be indoor, simplex type construction, vertical free standing,floor mounted type, metal clad suitable for installation at 50 degree centigradeambient. Panel enclosure shall be fabricated from 2 mm thick sheet steel andthe same shall be IP 52 protected. For further details of scheme, referencemay please be made to ANNEXURE-C

5.25.00 Accessories

5.25.01 Following accessories shall be furnished along with the Switchgear :

a. Earthing equipment suitable for earthing the bus or outgoing cable.

b. Test cabinet with coupling cables for testing the breaker in draw out

position.

c. Sufficient quantity of trolley shall be provided with jacking facility to drawout the HT breakers from the cubicle and to transport to the workingbench for testing and maintenance purpose. These trolleys shall bearranged for HV and LV Breakers.


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6.00.00 TESTS

6.01.00 The switchgear shall be completely assembled, wired, adjusted and tested atthe factory as per the relevant standards of IS & IEC.

6.02.00 Routine Test

6.02.01 The tests shall generally include but not necessarily limited to the following:

a. Operation under simulated service condition to ensure accuracy ofwiring, correctness of control scheme & proper functioning of theequipment.

b. All wiring and current carrying part shall be given appropriate HighVoltage test.

c. Primary current and voltage shall be applied to all instrumenttransformers.

d. Routine test shall be carried out on all equipment such as circuitbreakers, instrument transformers, relays, meters etc. as per relevantstandard.

6.03.00 Type Test

6.03.01 Following minimum tests shall be performed on a typical section of the busassembly:

a. Impulse Test

b. Temperature rise Test

c. Short circuit Test

d. STC

e. Switching Over voltage Test

f. Mechanical Endurance Test

g. Degree of enclosure protection

h. Pressure relief device operation test

Charges for each of the above tests shall be indicated separately.

6.03.02 All tests shall be carried out at the manufacturers works under his care andexpense. All Type and Routine tests shall be witnessed by owners


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representative. Prior notice of minimum four (4) weeks shall be given to theowner for witnessing the tests.

7.00.00 List of Drawings and Documents to be submit ted with bid

a. Complete assembly drawings of the switchgear showing plan, elevationand typical sectional views and locations of the breaker compartment,cable terminations, busbar chamber, metering and relay compartmentand terminal blocks for external connections.

b. Switchgear interface panel drawing showing the layout of terminalblock, cabling etc.

c. Drawings of matching flanges and terminals for busducts

d. Typical and recommended schematic diagrams for control and supervisionof circuit breakers.

e. Reports of all type tests of representative sections of panel assemblies.

f. Sizing Calculations for bus size selection.

g. Type tests certificates of CT, VT and Breakers


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ANNEXURE-A

RATINGS AND REQUIREMENTS

1.0 SWITCHGEAR

1.1 General

Type : Metal-clad, draw out

Service : Indoor

Enclosure : IP 5X

1.2 System

Rated Voltage KV rms : 11kV and 3.3kV 10%

Phase : Three

Rated Frequency : 50 Hz 5%

System grounding : Non-Effectively Earthed

1.3 Rated Current inside the cubicle andat an ambient temperature of 50oC :

Bus bar : *A (for 11kV) and*A (for 3.3kV)

Circuit breaker : *A (for 11kV) and*A (for3.3 kV)* Bidder to furnish

1.4 Short Circuit Rating

Rated short time withstand current : 40kA minimum.

Duration : 3 Sec.

Rated peak withstand current : 100kA minimum.

1.5 Insulation level :

Rated lightning impulse withstand : 75KVpeak (for 11kV)voltage &

40kVpeak (for 3.3kV)


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Rated one-minute power frequency : 35KVrms (for 11kV)withstand voltage &

10kVrms (for 3.3kV)

1.6 AC/DC Power Supply

Control voltage : 220 V DC (+10% to 15%)

Service voltage : 240V 10%, 1 Ph, 50 Hz 5%

1.7 Termination details

Incomer/ Tie feeder : Through bottom entry cable or busduct, top/bottom depending onrequirement.

Outgoing feeder : Through bottom entry cable,

2.0 CIRCUIT BREAKER

1.0 Type : SF6

2.0 No. of poles : Three

3.0 Rated Voltage KV rms : 11kV and 3.3kV 10%

4.0 Rated Frequency Hz : 50 5%

5.0 Rated normal current atsite condition Amps : *A(for 11kV) and

*A (for 3.3 kV)* bidder to furnish

6.0 Reference Standard : IEC-62271, 60694, 61233,IS-12729

7.0 Rated Insulation Level

7.1 Lightning Impulse withstand voltage : 75 kV peak (for 11kV)40 kV peak (for 3.3kV)

7.2 Rated one minute power frequencywithstand voltage : 35 kVrms (for 11kV)

10 kVrms (for 3.3kV)

8.0 Mechanical Endurance Class : M1

9.0 Electrical Endurance Class : E1

10.0 Restrike Probability Class : C1

11.0 First pole to clear factor : As per IEC


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12.0 Rated Operating Sequence : O - 3m - CO - 3m - CO

13.0 Operating mechanism : Motor wound Spring charging

14.0 % DC Component : 35%

15.0 Operating time

15.1 Opening time (ms) : Not more than 60

15.2 Closing time (ms) : Not more than 100

16.0 Rated Supply Voltage andfrequency for

16.1 Closing : 220 V DC, (+10%V to 15%V)

16.2 Tripping : 220V DC, (+10%V to 30%V)

16.3 Spring Charge Motor : 220V DC, (+10%V to 15%V)

16.4 Heater/Lamp/Socket : 240V(10%),1 Ph,50Hz(5%),2W


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ANNEXURE-B

PROTECTIONS

1.0 Minimum protections to be provided for different type of circuits are listed below-All numerical protection relay shall have communication with EDMS by suitableprotocol which shall be hooked up with DDCMIS. The relay shall have selfdiagnostic features.

A. Incomer : 1-multifunction Numerical relaycomprising of the followingprotective elements -

a. Over current (50/51) forphase fault with timer (2)

b. Over current (50N/51N) forearth fault with timer (2)

c. IDMTL over current(51SN) for stand by earthfault (for incomer fromtransformer only).

.d. Restricted E/F (64) (for

incomer from transformer

only)

e. Under voltage with timedelay (27)

f. VT fuse failure

B. Tie feeder : 1-multifunctionNumerical relay withcomprising of the followingprotective elements -



c. Under voltage with timedelay (27)

.d. VT fuse failure


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: 1-numerical synchronizing check

relay, if applicable, complete withguard relay and hard wires.

C. Motor feeder : 1-multifunction Numerical relaywith motor protection relay (99) forprotection against -

a. Thermal overload (49)

b. Phase fault (50)

c. Unbalance (-Ve seq.) (46)

d. Locked rotor (50 LR) (ref.

note 6)

: 1-Definite time O/C relay (50G)for earth fault (through CBCT)

: 1-Differential relay (87) for motorabove 1000 KW rating.

D. Auxiliary Transformer : 1-multifunction Numerical relaycomprising of the followingprotective elements -

a. Over current (50/51) for

phase faults with timer (2)b. Differential protection (for

transformers rated 5MVAand above)

: 1-Definite time O/C relay (50G) forearth fault (through CBCT)

: Flag relays for transformer gas. oiltemperature and windingtemperature alarm and trip.

E. Line feeder : 1-multifunction Numerical relay

comprising of the followingprotective elements -




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2.0 In case any trip function is not available in a single relay, separate numerical

relays shall be provided to achieve the requirement.

3.0 Apart from protection relays, each breaker shall be provided with anti-pumping(94), trip annunciation (30), trip supervision (74), electrically reset type breakercontact multiplication (52X) relay and lockout (86) relay. Lockout relay shall behand reset type.

4.0 Numerical under voltage relays (27) with time delay relay including VT fusefailure relay shall be provided for Bus VTs.

5.0 IDMTL relay version shall be decided as per system requirement and the sameshall be finalized during detail engineering.

6.0 Zero-sequence CT and associated relay combination shall be such as to

ensure a pick-up sensitivity of 10A primary ground fault current.

7.0 Separate locked rotor protection relay (50 LR) with auxiliary relay (50 LRX)shall be furnished, if required.

8.0 All the above Numerical relays shall have communication with EDMS forparameterization and DR upload with necessary password protection, whichshall in turn will have connectivity with DDCMIS


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ANNEXURE-C

BUS TRANSFER SCHEME

1.0 Bus transfer scheme (BTS) shall be provided, when specified, between twoswitchgears connected through tie-breakers (or bus coupler breaker between twobus sections) and fed independently from two upstream power sources.

1.1 Bus transfer could be manual (planned transfer) in the event of transfer of load fromone source to the other or automatic when fault is characterized by operation ofprotective relay.

The manual and automatic bus transfer shall be arranged in such a way that any of

he following mode of operation is possible.

2.0 Manual Bus Transfer

2.1 Without voltage interruption

This means by allowing momentary parallel operation of two sources.

2.2 With voltage interruption

a) Slow Transfer

b) Fast Transfer

3.0 Automatic Bus Transfer

3.1 With Voltage Interruption

a) Slow Transfer

b) Fast Transfer

3.2 In Phase Transfer mode

4.0 The requirement under various modes of bus transfer are further detailed as under :

4.1 Manual bus transfer withou t voltage interruption

In this mode, two sources are allowed to operate in parallel for short duration. Facilityshall be provided to bypass the normal interlock against parallel operation. Thechangeover involves check synchronizing the two sources whenever the breaker fornew source of supply is closed. Closure of new source breaker gives trippingcommand to the existing source breaker automatically.


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However, this mode of operation is generally not used in normal course, as itinvolves paralleling of two sources, however briefly, which may give rise to the fault

level beyond the specified withstand and rupturing capacity of circuit breakers. Thisscheme shall therefore be used, with due precautions, only in case of emergencywhen other modes of bus transfers are not available.

4.2 Manual bus transfer with voltage interruption

Under this condition bus transfer is either Slow transfer or Fast transfer.

Slow Transfer

This changeover consists in switching off the existing source of supply and allowingthe residual voltage of motors connected to the bus to decay sufficiently, (about 20%of the rated voltage) where after only the impulse goes to the breaker of new sourceof supply for closure.

Necessary VTs and voltage sensing relays are used for sensing the appropriatevoltage condition for bus transfer. This ensures that at the moment of bus transfer,even if residual voltage of motor is in phase opposition to the voltage of new sourceof supply, the motors shall not be subjected to magnetic shock.

To avoid the excessive voltage drop due to simultaneous restarting of all motorsconnected to the existing bus, some of the pre selected non-essential motors andother loads are switched off in this scheme along with the existing source breaker.This allows the bus voltage drop during restarting the motors to remain withinacceptable limit. The details of selection scheme for automatic tripping of such

motors is decided during detail engineering.

Fast Transfer

In this mode of bus transfer the existing source breaker is switched off and the newsource breaker is closed. The switchover is so rapid that the vector differencebetween motor residual voltage and the new source voltage is very little so thatclosure of breaker against phase opposition is not encountered. On the other hand,at the time of closure, speed of connected motors drops down only marginally, withthe result that at the moment of transfer of motors loads to the new source of supply,there is only a small rise in current as compared to the normal running current ofmotors. The voltage drop during this transfer is therefore marginal and bus transfer issatisfactory.

Since the closing time of breaker is considerably longer than the tripping time, thisscheme gives the closing command to the new source breaker first and only after apreset time interval it gives the tripping command to the existing source breaker. Theinterval between these two commands is so selected that the actual interruption timeis limited to few cycles.


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4.3 Automatic bus transfer with voltage interruption

As compared to the bus transfer described under 4.2 above, the changeover in thismode of transfer is initiated automatically upon sensing under voltage in the existingbus. Thus with the help of appropriate sensing relays, the bus transfer takes placeautomatically when the existing bus voltage drops below a certain voltage level(about 85 % of the rated voltage) for a preset time. This scheme initiates bus transferonly in case of external faults responsible for voltage drop. In case of voltage dropdue to internal fault, the transfer scheme is locked out.

The automatic bus transfer scheme is generally a fast bus transfer scheme and thesequence of operation are similar to that explained in fast bus transfer scheme inmanual mode. However, if the fast bus transfer is found not responding to thecommand-, it shall automatically go for slow bus transfer scheme in a manner

explained against slow bus transfer scheme under manual mode.

4.4 In Phase bus Transfer

The breaker power contacts shall close when the decaying and drifting bus voltagesynchronizes with the incoming source voltage within acceptable voltage andfrequency parameters. The bus transfer system shall continuously process the busvoltage and drifting phase angle dynamics to determine using second orderpredictive algorithm in real-time, the exact moment of sending a command to thebreaker-closing coil to achieve the above.

5.0 General requirement

The equipment for bus transfer scheme described above shall be wired in separatepanels. The equipment shall include selector switches, indicating lamps, transfercircuit, supervising relays, Numerical based fast acting voltage sensing relay andphase comparison relays etc. Necessary voltage transformers of required accuracyclass shall be provided in appropriate high voltage switchgear panels. Auxiliary relaysshall be incorporated with a view to enable inter panel wiring and easy fault location.

Testing facility shall be provided for on line testing of the operating circuits of eachbus transfer scheme. However, in case need arises for automatic changeover, whentesting of schemes are in progress the automatic changeover operation shall overridethe testing activities by resetting the test circuits.

Necessary selector switches shall be provided to select the mode of transfer i.e.,

manual or automatic. In case of manual transfer, there shall be additional selectorswitch for selecting manual without voltage interruption, manual fast and 'manualslow changeover with voltage interruption. Mode selection and bus transfer initiationswitches shall be located in the control panel.


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The supervision of operating circuit of each mode of bus transfer shall be duly

signalised in the control room. All relevant indication and annunciation with audible

alarm, accept and reset facility shall be provided. Facility shall also exist in the form ofpotential free auxiliary contacts for remote annunciation. Similarly actuation of any

mode of bus transfer either manual or automatic shall also be signaled together with an

audible alarm in the control room. Certain important information of bus transfer event is

to be recorded in the data acquisition system. Necessary potential free contacts shall

be kept wired for event logging.


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SPECIFICATION E13

415V POWER CONTROL CENTER (PCC), MOTOR CONTROL CENTER (MCC),

AC DISTRIBUTION BOARDS, DC STARTER PANEL & MISCELLANEOUS PANELS AND

EQUIPMENTS

CONTENTS

CLAUSE NO. DESCRIPTION PAGE NO

1.00.00 General 1

2.00.00 Description 1

3.00.00 415V PCC 4

4.00.00 MCC & DB 13

5.00.00 DC Starter Panel 25

6.00.00 Miscellaneous Panels And Equipments 25

7.00.00 List of Drawing and Document to be submitted with bid 27

ATTACHMENTS

ANNEXURE - A Ratings and Requirements for PCC 28

ANNEXURE -B Ratings and Requirements for MCC & DB 30


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SPECIFICATION E13

415V POWER CONTROL CENTER (PCC), MOTOR CONTROL CENTER (MCC),

AC DISTRIBUTION BOARDS, DC STARTER PANEL & MISCELLANEOUS PANELS AND

EQUIPMENTS

1.00.00 GENERAL

The AC Power Supply (415 Volt) System shall provide power to 415-volt plantauxiliary loads and include over-current phase and earth fault protection. The ACPower Supply (415 Volt) System shall consist of the following major components:-

Unit/Station Service Transformers (USTs/SSTs)

LT Busduct

Unit and Station Service Switchgears (USS/SSS)

Power Control Centres (PCCs) & Motor Control Centres (MCCs)

415V AC Distribution Boards (ACDBs)

Raceways, Conduits, Conductors and Conductor Accessories.

This specification shall cover the requirements of followings.

a) Power Control Center (PCC)

b) Motor Control Center (MCC)

c) AC Distribution Board (ACDB)

d) DC Starter Panel (DCSP)

2.00.00 DESCRIPTION

The unit & station service transformers (USTs/SSTs) shall transform 11000Vthree-phase power, supplied by the HV AC Power Supply System, to 3300V &415V three-phase power. The transformers shall supply 3300V / 415 Volt three-phase power to USS/SSS buses through a main breaker. The bus arrangement is

shown in attached SLD. The main and bus-coupler breakers shall make it possiblefor a switchgear bus to be fed from two separate sources with auto & manual livechangeover facilities. Normally each half section of the switchgear will be fed by itsown incomer with the bus-coupler being open. In case of loss of supply from theincomer, under-voltage actuated dead changeover to the other source shall takeplace by tripping of affected incomer and closure of bus-coupler breaker. Uponrestoration of normal supply, the incomer breaker will be closed after parallelingand the pre-selected breaker will be either automatically or manually tripped thuseffecting a live changeover.


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The 415V system shall be a solidly grounded wye system. The Motors rated below160 kW shall be supplied from the 415 volt system.

The USS/SSS shall distribute power through feeder breakers to 415V motors ratedabove 75 KW and to Motor Control Centres (MCC). The MCCs shall distributepower to small 415 volt motors, to AC distribution boards and to intermediate415 volt loads. The MCCs shall also distribute power to the single phase ACPower Supply (240 Volt) System. The 415 volt AC distribution boards shall dis-tribute power to small 415 volt loads.

For offsite areas beyond power block, separate independent PCCs will beprovided. All PCCs will be fed through respective 2x100% redundant 11/0.433kVtransformers through two incomer breakers. Power to these transformers will befed from 11kV as shown in SLD. Load centre MCCs in offsite areas will be fed fromrespective area PCCs through two feeders each. Bidder shall decide the actual

number of transformers and LV boards based upon the power distributionarrangement proposed based on geographical location and unit/station loads.

Remote control from the control room shall be provided for Unit/station PCC mainand bus-coupler breakers from EDMS HMI and remote start, stop andON/OFF/TRIP, remote/local indication for all motor modules shall be providedfrom DDCMIS. Monitoring shall be provided for AC Power Supply (415 Volt)System conditions. Abnormal conditions shall be alarmed to EDMS/DDCMIS.

The normal operating conditions for the 415V AC System are as listed:-

a) Unit and/or station transformer supplying power through the 11000 voltbuses to the unit/station service transformers.

b) USS bus incomer breakers closed.

c) USS bus bus-coupler breaker open.

d) 415V auxiliary load at level required for full load operation of the unit.

The Off-Normal or Emergency Operating Conditions include the following:

a) One UST supplying power to two USS buses.

b) One SST supplying power to two SSS buses.

c) Phase-to-ground, phase-to-phase, or three-phase faults on USS, SSS orMCC or distribution board feeder. Phase-to-earth fault currents shall belimited by the UST/SST size i.e. 1600 kVA/2000 kVA/2500KVA.

The 415V PCC, MCC with two incomers and one bus coupler (allelectrically operated ACB controlled) and as required number of active andspare outgoing feeders for control of various LT drives and loads shall beconsidered.


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All LV switchgears and Motor Control Centres shall be intelligent type utilisingfeeder management devices for protection, control, monitoring and

measurement on each breaker controlled incomer, bus coupler, tie-feederand breaker-controlled large motor feeders. The data shall be transmitted ona serial fibre-optic cable link to an EDMS/DDCMIS system in the Main PlantControl Room. The feeder units shall provide self-diagnostic and historicaldata logging facilities. Each 415V switchgear will be served by 2x100%capacity service transformers

Each ESP PCC will be fed from 11kV unit switchgear located in powerhousebuilding via a pair of dry type LT transformers to be installed on either side ofESP PCC. The PCC comprising of two incomer and one bus coupler withadequate number of feeders for ESP, control building lighting, Airconditioning, Ventilation system and equipment handling system (Hoists), firefighting system load shall be complete in all respect and will serve as power

distribution center. The welding power requirement shall be through separateservice transformer as shown in SLD.

2.01.00 CONTROL ROOM ALARMS/INDICATION/SER POINTS

All switchgear located in the TG building shall be controlled from CRTs(EDMS) in the unit control room, other than those controlled from DCS.The switchgear of ash handling and coal handling systems shall becontrolled from the respective system control panels. Other MCCs viz. fueloil pump house MCC, water treatment plant MCC, clarifier/misc waterpump house MCC, ESP MCC, etc shall be locally controlled withsynchronization equipment facility mounted on the switchgear. Hesesystems shall be monitored from CRTS in CCR. For all switchgear/MCC

where auto/manual changeover facility is specified, breakers shall beprovided for the incomers and bus coupler.

The control room CRTs shall provide indication & alarms for the 415Vauxiliary supply as given below. Any additional indications/alarmsconsidered necessary during detailed engineering shall also be provided.Some of these shall be selected for sequential events recording. For eachbreaker and bus, grouped alarm for any abnormal conditions shall beprovided in the control desk.

(a) Status indication in CRT (EDMS/DCS)

Breaker onBreaker off

Breaker fault

Breaker service

Breaker selected for remote

Load current

Bus Voltage

Trip Circuit Healthy


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Control DC ON

(b) Alarms in CRT

Breaker auto tripped/L/O Relay operated

Bus under voltage

Sources paralleled beyond preset time

Common outgoing feeder fault

Incoming 220 V DC control supply failed

Bus PT fuse failed

Bus PT not in service

3.00.00 415V PCC

3.01.00 The PCCs shall be indoor, metal clad, floor mounted suitable for location in aclean but hot humid and tropical atmosphere. Degree of protection shall beIP 54. Sheet steel used for the construction shall be minimum 2mm thick forstructural load bearing members, doors, covers and partitions. The designand construction shall be such as to allow extension at either end.

3.02.00 The PCC shall be rated for 50kA for one (1) second.

3.03.00 The PCC shall have sectionalized bus with two incomers and two bussections. PCC shall be provided with permanent alternative supply forflexibility of operation and to cater for planned or forced outages.

3.04.00 PCC cubicles shall be component wise compartmentalized so that failure ofone equipment shall not affect the equipment in adjacent compartment oradjacent cubicle. Circuit breaker in switchgear cubicle shall be draw out typeand not more than one circuit breakers shall be located in a vertical panelwith metallic partitions in between the breakers. The working height shall belimited within 400 mm to 1800 mm from floor level.

3.05.00 Each breaker shall be housed in a separate cubicle complete with anindividual front access door. Each vertical section shall have a removableback cover.

All doors and covers shall be provided with neoprene gaskets. The doorshall have self-tightening handle/knob so as to prevent ingress of dust.

3.06.00 PCC cubicle shall be so sized as to permit closing of the front access doorwhen the breaker is pulled out to ISOLATED position.

3.07.00 All switches, push buttons, lamps, indicating instruments shall be flushmounted on the respective cubicle door whereas relays and otherauxiliary devices may be mounted on a separate cubicle.


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3.08.00 The PCC shall have 2 X100% incomer at two extreme end of line up. Theincomer, bus couplers, breakers/ isolators for the PCC shall be four- (4) pole

type. All breakers shall be compatible for 220 V DC system.

20% spare feeders, minimum one (1) of each rating and type shall beprovided.


i. The main buses and connections shall be of high conductivityAluminium/Aluminium alloy, sized for specified current ratings withmaximum temperature limited to 85

oC (i.e., 35

oC rise over 50

oC

ambient) for normal operating condition and 200 0 C for short circuitcondition.

ii. All bus connections shall be silver-plated. Adequate contact pressureshall be ensured by means of two-bolt connection with plain & springwashers and locknuts.

iii. No Bi-metallic should be utilized in the power circuits of bus bar /cable areas. If unavoidable provide suitable Bi-metallic strips in thecorresponding zones.

iv. Bus bars and connections shall be fully insulated for working voltagewith adequate phase/ground clearances. Insulating sleeves for busbars and shrouds for joints shall be provided. Sleeves shall be nonmoisture absorbent type.

v. Bus insulators shall be flame-retardant, non-hygroscopic, trackresistant type with high creepage surface.

vi. All buses and connections shall be supported and braced to withstandthe stresses due to maximum short-circuit current and also to takecare of any thermal expansion.

vii. Bus bars shall be colour coded for easy identification and so locatedthat the sequence R-Y-B shall be from left to right, top to bottom orfront to rear, when viewed from the front to switchgear assembly.

viii. Bolted disconnect links shall be provided for all outgoing feeders forisolation of neutral, if necessary.

ix. Heat shrinkable PVC sleeves having flame retardant property shall beprovided on each bus bar.

x. Vertical neutral bus bar shall be brought for each panel. Neutral busbars shall have minimum 50% of the rating of main bus bar.

xi. The vertical busbar take-off leads shall be provided with adequateclearance to avoid flashovers due to arc jump/ionization of air.


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xii. Main buses shall be of aluminium and shall be rated to carry themaximum rated incomer transformer load current. The incomers shall

be sized to supply all non-redundant loads on both sections of theswitchgear (with one transformer out of service and tie-breakerclosed).

xiii. CAUTION LIVE BUS BARS inscribed label shall be provided onbarriers / covers.


i. Circuit Breaker shall be four pole, single throw, air break type withstored energy, trip free mechanism and shunt trip.

ii. Circuit breakers shall be draw out type, having SERVICE, TEST &

ISOLATED positions with positive indication for each position.

iii. Circuit breakers of identical rating shall be physically and electricallyinterchangeable.

iv. Circuit breaker shall have motor wound spring charged trip freemechanism with anti-pumping feature and shunt trip. In addition,facility for manual charging of spring shall be provided.

v. For motor wound mechanism, spring charging shall take placeautomatically after each breaker closing operation. Oneopen-close-open operation of the circuit breaker shall be possible afterfailure of power supply to the motor.

vi. Mechanical safety interlock shall be provided to prevent the circuitbreaker from being racked in or out of the service position when thebreaker is closed and to prevent racking in the circuit breaker unlessthe control plug is fully engaged.

vii. Safety interlock shall be provided for the followings: -

a. Operation of CB shall not be possible unless it is fully inservice position, fully withdrawn to test position or fully drawn-out.

b. Compartment door of the breaker shall not open unless theassociated breaker is in open position.

c. The breaker of specific breaker rating shall be prevented fromengaging into the stationary portion of other higher rating.

d. The breaker carriage shall be earthed before main circuitbreaker contacts are plugged in. The earthing shall bemaintained in service position.


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viii. Automatic safety shutters shall be provided to fully cover the femaleprimary disconnects when the breaker is withdrawn.

ix. Each breaker shall be provided with an emergency manual trip,mechanical ON-OFF indicator, an operation counter and mechanismcharge/discharge indicator.

x. Each breaker shall be provided with followings: -

a. Auxiliary switch, with 6NO+6NC contacts, mounted on thedrawout portion of the PCC.

b. Position/cell switch with 4NO+2NC contacts, one each for

c. TEST and SERVICE position.

d. Auxiliary switch, with 6NO+6NC contacts, mounted on thestationary portion of the PCC and operated mechanically by asliding lever from the breaker in SERVICE position.Alternatively electrically latching relay may be used for thepurpose.

xi) LT circuit breaker provide with in-built over-current, short circuit, undervoltage and earth fault releases with shunt trip coil can be adoptedinstead of providing separate relay for each protection.

Limit/auxiliary switches shall be convertible type, that is, suitable forchanging NO. contact to N.C. and vice-versa. Switch contact rated for

10A A.C. and 2A D.C. at operating voltage.

3.11.00 Control Modules

i. Draw out type control module shall have self-aligning power/controldisconnects. All disconnects shall be silver-plated to ensure goodcontacts.

ii. The design shall be such as to permit easy withdrawal/reinsertion ofthe unit with guide rails to ensure correct alignment.

iii. Control Module shall house the control components for a circuit suchas switch, fuse, lamps etc.

iv. Various module/compartment sizes shall be multiple of one basic unitto facilitate modification at site. Suitable provision for this purposeshould also be incorporated in the vertical bus bars.

v. Drawout type control modules of same size and type shall beelectrically and physically interchangeable.


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vi. The commands from DDCMIS/EDMS shall be wired up to theswitchgear through interposing relays to avoid mix up of 24 V DC and

220VDC in DDCMIS/EDMS system.

vii. The motor space heaters shall be controlled from separate module inMCC with necessary interlocks with the main motor.

viii. The wiring for space heaters of Switchgear compartments shall besegregated from the control wiring

ix. Double decker lyra contacts for higher capacity LT motors modulesand feeder modules for increasing the contacts surface area to avoidflash over of LT motors.

3.12.00 Switches

i. Switches shall be three pole, air break, AC22 heavy duty for powerfeeders.

ii. The switch shall have a quick-make, quick-break mechanism operatedby a suitable external handle, complete with position indicator.

iii. This handle shall have provision for padlocking in ON and OFFposition.

iv. Barriers shall be provided to prevent inter-phase arcing and liveterminals shall be shrouded to avoid accidental contact.

v. The compartment door shall be interlocked mechanically with theswitch such that the door cannot be opened unless the switch is inOFF position. Means shall be provided for releasing this interlock atany time.

vi. Switches shall be capable of withstanding the let-through fault currentof back-up fuses or circuit breakers.

vii. Outgoing feeders shall be provided with bolted disconnect link forisolation of neutral, if necessary.

3.13.00 The circuit breaker shall be wired up for local & remote operation withLocal/Remote selector switch. Each breaker cubicle shall be equipped with

following: -

i. One (1) 'TRIP-NEUTRAL-CLOSE' breaker control switch spring returnto neutral type pistol grip handle.

ii. One (1) LOCAL REMOTE selector switch stay put type with pistol griphandle and key interlock for all non-motor feeders.

iii. Five (5) indicating lamps on front of compartment: -


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GREEN Breaker open

RED Breaker closed

AMBER Trip

WHITE Trip circuit healthy

BLUE Spring charged

3.14.00 Lamps shall be front loading clustered type LED module pilot lights inthermoplastic enclosure with polycarbonate lens and diffuser. LED shall beprotected by in-built fuse with surge suppressor and leakage voltage glowprotection. Lamp and lens shall be replaceable from front. LEDs used forindication shall have pick up and drop out voltage within -20% of the operating

voltage.

3.15.00 Current Transformer

i. Current Transformers shall be cast-resin type. All secondaryconnections shall be brought out to terminal blocks where wye or deltaconnection will be made.

ii. Accuracy class of the current transformers shall be: -

a. Class 5P20 & PS for relaying.b. Class 0.5 for metering.

3.15.01 The fixing and termination arrangement of feeder CTs shall have easy accessfor testing and changing.

3.15.02 CT secondaries shall have terminations with link T.Bs for shorting.

3.16.00 Voltage Transformer

i. Voltage transformers shall be cast-resin, drawout type and shall havean accuracy class of 0.5 and 3P. Voltage transformer mounted onbreaker carriage is not acceptable.

ii. High voltage windings of voltage transformer shall be protected bycurrent limiting fuses. The voltage transformer and fuses shall be

completely disconnected and visibly grounded in fully drawoutposition.

iii. Low voltage fuses, sized to prevent overload, shall be installed in allungrounded secondary leads.


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3.17.00 Relays

i. Numerical, communicable multi function relay of latest version to beapproved by owner shall be provided for all breaker feeders coveringall protection. If some functions are not available in the multifunctionrelay, separate static discrete or electromechanical relays shall beprovided.

ii. The numerical relay shall have suitable communication port withmodbus protocol for connection to EDMS/.

iii. Relays shall be rated for operation on 1A secondary current and 110Vsecondary voltage; number and rating of relay contacts shall suit thejob requirements.

iv. The bidder shall furnish, install & co-ordinate all relays to suit therequirements of protection and interlock and bus transfer scheme.

3.18.00 Meters & Transducers

i. For all incomers and outgoing feeders multifunction digitalcommunicable meter shall be provided with display screen. If somefunctions are not available in the multifunction meter, separatediscrete meters shall be provided. The multifunction meter shall havecommunication port with modbus protocol for connection toEDMS/DDCMIS. The metering shall cover current, voltage, kW, kVAR,power factor, kWh and frequency. Auxiliary consumption shall bemetered.

ii. Discrete meters (96 x 96 mm) shall be Taut-band type, with 240o

scale, anti-glare glass and accuracy class of 2% full scale. Eachmeter shall have zero adjuster on the front.

iii. Transducers (Slim type), with + 0.5% accuracy, 4-20mA DC linearoutput & 750 ohm load shall be provided in transducer panel.

3.19.00 Secondary Wiring

i. PCC shall be fully wired at the factory to ensure proper functioning ofcontrol, protection, transfer and interlocking schemes.

ii. PCC shall be provided to permit individual circuit isolation from buswires without disturbing other circuits. All spare contacts of relays,switches and other devices shall be wired up to terminal blocks.

iii. Wiring shall be done with flexible, 1100V grade, PVC insulatedswitchboard wires with stranded copper conductors of 2.5 mm

2 for

control & current circuits and 1.5 mm2for voltage circuits.


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iv. Each wire shall be identified, at both ends, with permanent markersbearing wire numbers as per Contractor's wiring diagrams.

v. Wire terminations shall be made with crimping type connectors withinsulating sleeves. Wire shall not be spliced between terminals.

3.20.00 Terminal Blocks

i. Terminal blocks shall be 660V grade box-clamp type with markingstrips, similar to ELMEX 10 mm

2 or equal. Terminals for C.T.

secondary leads shall have provision for shorting.

ii. Not more than two wires shall be connected to any terminal. Spareterminals equal in number to 20% active terminals shall be furnished.

iii. Terminal blocks shall be located to allow easy access. Wiring shall beso arranged that individual wires of an external cable can beconnected to consecutive terminals.

3.21.00 Ground Bus

i. A ground bus, rated to carry maximum fault current, shall extend fulllength of the PCC.

ii. The ground bus shall be provided with two-bolt drilling with Cadmiumcoated bolts and nuts at each end to receive 50 x 6 mm Cu flat.

iii. Each stationary unit shall be connected directly to the ground bus.

The frame of each circuit breaker and draw out V.T. unit shall begrounded through heavy multiple contacts at all times except when theprimary disconnecting devices are separated by a safe distance.

3.22.00 Space Heaters and Plug Sockets

i. Each vertical section shall be provided with thermostat controlledspace heater and 5A, 3-pin plug socket.

ii. Cubicle heater, Plug-socket circuit shall have individual switch fuseunits.

3.23.00 A.C./D.C. Power Supply

i. The following power supplies will be made available to eachswitchgear:

A.C. supply: Double feeder

D.C. supply: Double feeder


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3.24.00 Isolating switch fuse units shall be provided at each PCC for the incomingsupplies, 4-pole, single throw for A.C. and 2- pole, double throw for D.C.

3.25.00 Painting

i. All surfaces shall be sand blasted, pickled and grounded as required toproduce a smooth, clean surface free of scale, grease and rust.

ii. After cleaning, the surfaces shall be given a phosphate coating followed bytwo coats of high quality primer and stoved after each coat.

iii. The switchgear shall be finished in Grade 631 of IS 5 with two coats ofEpoxy Paint. However, Owner reserves the right to change the color shadeat the time of approval of vendor drawings.

iv. Sufficient quantity of touch-up paint shall be furnished for application atsite.

3.26.00 PROTECTIONS

1.0 The minimum protections to be provided for different types of circuits arelisted below :

a. Incoming Feeder : O/C relays (50/51) for phase fault with& Bus Coupler timer (2)

O/C relay (50N/51N) for Earth fault withtimer (2).

Under voltage relay (27)

Neutral Displacement relay (NDR)

b. Outgoing Bkr. Feeder : O/C relays (50/51) for phase fault with timer(2)

O/C relay (50N/51N) for Earth fault withtimer (2).

2.0 Apart from protection relays, each electrically operated breaker shall beprovided with antipumping (94), trip annunciation (30), lockout (86),lockout supervision (95) and trip supervision (74) relays. Lockout relayshall be hand reset type.

3.0 Fuse monitoring relay (98) shall be provided on the secondary side ofvoltage transformer to monitor fuses.


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3.27.00 TESTS

i. The PCC shall be completely assembled, wired, adjusted and tested at thefactory as per the relevant standards of IS & IEC in the presence of theowners representative.

ii. The following Routine and Type tests shall be performed for each PCC panel.

Routine Test

The tests shall include but not necessarily be limited to the following :

a. Operation under simulated service condition to ensureaccuracy of wiring, correctness of control scheme & properfunctioning of the equipment.

b. All wiring and current carrying part shall be given appropriateHigh Voltage Test.

c. Primary current & voltage shall be applied to all instrumenttransformers.

d. Routine test shall be carried out on all equipment such ascircuit breakers, instrument transformers, relays, meters etc.

Type Test

The following test shall be performed on a typical section of the bus assembly

with breaker in cubicle.

a. Temperature rise Test

b. Short circuit Test

4.00.00 MCC & DB

4.01.00 The MCCs shall be indoor, metal clad, floor mounted suitable for location in aclean but hot humid and tropical atmosphere. Sheet steel used for theconstruction shall be minimum 2mm thick for structural load bearing members,doors, covers and partitions. MCCs shall be double front draw out type whileDB shall be single front fixed type. The design and construction shall be suchas to allow extension at either end.

4.02.00 The MCC/ DB shall be rated for 50kA for one (1) second.

4.03.00 Degree of protection for both MCC and DB shall be IP 54.

4.04.00 MCC / DB assembly shall comprise of a continuous line up of dead front,freestanding vertical sections, housing the control modules in multitierformation.


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4.05.00 The design shall be fully compartmentalized with metal / insulating partitions

between compartments. The working height shall be limited within 400 mmto 1800 mm from floor level.

4.06.00 Each control module of MCC / DB shall be housed in a separatecompartment, complete with an individual front access door. Each verticalsection shall have a removable back cover. All doors and covers shall beprovided with neoprene gaskets. The door shall have self-tightening handle /knob so as to prevent ingress of dust.

4.07.00 All lamps, switches, push buttons, indicating instruments, relays shall beflush / semi-flush mounted on respective module compartment. MCC shallhave start and stop facility for all the drives.

4.08.00 20% spare feeders, minimum one of each rating and type shall be provided.


i. The continuous current rating for incomer, bus section and bus bar shallbe based on total continuous running load plus highest load during changeover of equipment / stream (one at a time) as applicable plus 25% of totalconnected intermittent loads plus 20% overall margin

ii. The main buses and connections shall be of high conductivity Aluminium /Aluminium alloy, sized for specified current ratings with maximumtemperature limited to 85

oC (i.e., 35

oC rise over 50

oC ambient) for normal

operating condition and 2000 C for short circuit condition. Vertical bus bars

shall be provided for each vertical panel.

iii. All bus connections shall be silver-plated. Adequate contact pressure shallbe ensured by means of two-bolt connection with plain and spring washersand locknuts.

iv. No Bi-metallic should be utilized in the power circuits of bus bar / cableareas. If unavoidable provide suitable Bi-metallic strips in thecorresponding zones.

.v. Busbars and connections shall be fully insulated for working voltage with

adequate phase/ground clearances. Insulating sleeves of non moistureabsorbent type for busbars and shrouds for joints shall be provided.

vi. Bus insulators shall be flame retardant, track-resistant type with highcreepage surface.

vii. Busbars & connections shall be supported and braced to withstand thestresses due to maximum short circuit current and also to take care of anythermal expansion.


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viii. Busbars shall be colour coded for easy identification and so located thatthe sequence R-Y-B shall be from left to right, top to bottom or front to

rear when viewed from the front of the assembly.

ix. Vertical neutral busbars shall be brought for each panel.

x. Bidder to ensure that for panels, ionized gas travel (due to fault) frommodule to bus bar chamber or from vertical bus bar to horizontal bus barchamber or from module/vertical bus bar chamber to cable alley/compartment shall be effectively restricted to prevent multiple fault/reducedamage. The vertical busbar take-off leads shall be provided withadequate clearance to avoid flashovers due to arc jump/ionization of air.

xi. Main bus bar shall run horizontally at the top for easy accessibility.

xii. CAUTION LIVE BUS BARS inscribed label shall be provided onbarriers/ covers.

xiii. Adequately rated copper auxiliary bus bars shall be provided for:

a. Panel & motor space heaterb. AC & DC control supplyc. P.T. supply

xiv. Heat shrinkable PVC sleeves having flame retardant property shall beprovided on each bus bar.


i. Circuit Breaker shall be four pole for incomer and bus coupler andthree pole for out going motor feeders, single throw, air break typewith stored energy, trip free mechanism and shunt trip.

ii. Circuit breakers shall be drawout type, having SERVICE, TEST &ISOLATED positions with positive indication for each position.

iii. Circuit breakers of identical rating shall be physically and electricallyinterchangeable.

iv. Circuit breaker shall have motor wound spring charged trip freemechanism with anti-pumping feature and shunt trip. In addition,facility for manual charging of spring shall be provided.

v. For motor wound mechanism, spring charging shall take placeautomatically after each breaker closing operation. Oneopen-close-open operation of the circuit breaker shall be possible afterfailure of power supply to the motor.

vi. Mechanical safety interlock shall be provided to prevent the circuitbreaker from being racked in or out of the service position when the


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breaker is closed and to prevent racking in the circuit breaker unlessthe control plug is fully engaged.

vii. Safety interlock shall be provided for the followings: -

a. Operation of CB shall not be possible unless it is fully inservice position, fully withdrawn to test position or fully drawn-out.

b. Compartment door of the breaker shall not open unless theassociated breaker is in open position.

c. The breaker of specific breaker rating shall be prevented fromengaging into the stationary portion of other higher rating.

d. The breaker carriage shall be earthed before main circuitbreaker contacts are plugged in. The earthing shall bemaintained in service position.

viii. Automatic safety shutters shall be provided to fully cover the femaleprimary disconnects when the breaker is withdrawn.

ix. Each breaker shall be provided with an emergency manual trip,mechanical ON-OFF indicator, an operation counter and mechanismcharge/discharge indicator.

x. Each breaker shall be provided with followings: -

a. Auxiliary switch, with 6NO+6NC contacts, mounted on thedrawout portion of the MCC.

b. Position/cell switch with 4NO+2NC contacts, one each forTEST and SERVICE position.

c. Auxiliary switch, with 6NO+6NC contacts, mounted on thestationary portion of the PANEL and operated mechanically bya sliding lever from the breaker in SERVICE position.Alternatively electrically latching relay may be used for thepurpose.

xi. Limit/auxiliary switches shall be convertible type, that is, suitable forchanging NO. contact to N.C. and vice-versa. Switch contact ratedfor 10A A.C. and 2A D.C. at operating voltage.

4.11.00 Control Modules

i. Drawout type control module shall have self-aligning power/controldisconnects. All disconnects shall be silver-plated to ensure goodcontacts.


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ii. Double decker lyra contacts for higher capacity LT motors modulesand feeder modules for increasing the contacts surface area to avoid

flash over of LT motors

iii. The design shall be such as to permit easy withdrawal/reinsertion ofthe unit with guide rails to ensure correct alignment.

iv. Control Module shall house the control components for a circuit suchas switch, fuse, lamps etc.

v. The equipment layout shall provide sufficient working space inbetween the components and subject to Owners approval.

vi. Various module/compartment sizes shall be multiple of one basic unitto facilitate modification at site. Suitable provision for this purpose

should also be incorporated in the vertical bus bars.

vii. Drawout type control modules of same size and type shall beelectrically and physically interchangeable.

viii. Selection and sizing of starter module shall comply with therequirement of IS 8554 Part- I.

4.12.00 Switches

i. Switches shall be three pole, air break, AC22 heavy duty for powerfeeders and AC23 heavy duty for motor feeders. Motor duty switchesshall be capable of safety maki