Auto%20transformerR4.pdf

7/29/2019 Auto%20transformerR4.pdf

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TECHNICALSPECIFICATIONSECTION:AUTOTRANSFORMER

CONTENT

SL.NO CL.NO. DESCRIPTION PAGENO.

1. 1.0 General 2

2. 2.0 Performance 3

3. 3.0 ConstructionDetails 4

4. 3.1.2 TankCover 5

5. 3.1.8 TemperatureIndicators 8

6. 3.3 Windings 10

7. 3.4 InsulatingOil 10

8. 3.5 TerminalArrangements 13

9. 3.9 TapChangingequipment 17

10. 4.0 Fittings 27

11. 5.0 InspectionandTesting 28

12. 5.2 FactoryTests 33

13. 5.2.7 TankTests 35

14. 6.0 Technicalparameters 39

15. 7.0 BushingCurrentTransformer 48

16. 8.0 OilStorageTank 52

17. 9.0 OilSamplingBottle 53

TECHNICALSPECIFICATIONSECTION:AUTOTRANSFORMER

Tech Specification,Section: Autotransformer Page 1 of 54C/ENGG/SPEC/TRF REV NO: 04


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1 General

1.1 This specification covers design, engineering, manufacture, testing atmanufacturer'sworks,deliveryatsiteincludingallmaterials,accessories,

spares,unloading,handling,properstorageatsite,erection,testingandcommissioningoftheequipmentspecified.

1.2 Theautotransformers shall ingeneral haveconstantohmic impedancebetweenHVandIVonalltaps.However,incaseofparalleloperationwiththeexistingtransformer,

i) The impedance, vector group, OLTC connection & range etc. of thetransformeristobematchedwiththatoftheexistingtransformer.

ii) Necessaryprovision is to be kept in the transformer controlscheme forparallel operationwiththeexistingMaster/Follower/Independent /Off type

OLTCcontrolscheme.iii) Matching of physical dimension, orientation etc. to facilitate

interchangeabilitywiththeexistingsparesinglephasetransformer,ifnecessary.

1.3 Externalor internalreactorsshallnotbeusedtoachievetheHV/LVandIV/LVimpedancespecified.

1.4ReferenceDrawings

Thelistofdrawingsindicatedbelowformapartofthisspecification.

i. StandarddimensionsforOIP 0000-T-E-A-001condenserbushings(Lowerportion)ii. Standardfoundationfor 0000-000-T-E-A-003 Autotransformeriii. Typicalarrangement 000S3-YE4-014ofautotransformerwithregulatingwindingattheendofserieswinding

1.5 Transportation

TheContractorshalldespatchthetransformerfilledwithoilorinanatmosphereofnitrogenordryair.Intheformercasethecontractorshalltakecareoftheweightlimitationontransportandhandlingfacilityatsite.In the latter case, necessary arrangement shall be ensured by thecontractortotakecareofpressuredropofnitrogenordryairduringtransitandstoragetill completionofoil fillingduringerection.Agas pressuretestingvalvewithnecessarypressuregaugeandadaptorvalveshallbeprovided.Transformershallalsobefittedwithsufficientnumberofimpactrecordersduringtransportationtomeasurethemovementduetoimpactinallthreedirections.

2 Performance

Tech Specification, Section: Autotransformer Page 2 of 54C/ENGG/SPEC/TRF REV NO: 04


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2.1 Theautotransformersshallbeusedforbi-directionalflowofratedpower.

2.2 Transformersshallbecapableofoperatingundernaturalcooledconditionuptothespecified load. Theforcedcooling equipmentshall comeintooperationbypre-setcontactsofwindingtemperatureindicatorandthe

transformershalloperateasaforcedcoolingunit initiallyasONAFuptospecified loadand thenasOFAF. Cooling shall be sodesigned thatduringtotalfailureofpowersupplytocoolingfansandoilpumps,thetransformershallbeabletooperateatfullloadforatleastten(10)minuteswithout the calculatedwinding hot spot temperatureexceeding 150C.Transformersfittedwith twocoolers,eachcapableofdissipating50percent of the loss at continuous maximum rating, shall be capable ofoperatingfor20minutesintheeventoffailureoftheoilcirculatingpumporblowersassociatedwithonecoolerwithoutthecalculatedwindinghotspot temperature exceeding 150C at continuous max. rating. Thecontractor shall submit supporting calculations for the above for

Employer'sapproval.

2.3 Thetransformersshallbecapableofbeingoperated,withoutdanger,on

any tapping at the rated MVA with voltage variation of 10%correspondingtothevoltageofthetapping.

2.4 ThemaximumfluxdensityinanypartofthecoreandyokeattheratedMVA, voltage and frequency shall be such that under 10 per centcontinuousovervoltageconditionitdoesnotexceed1.9Tesla.

2.5 DGA of oil shall be periodically monitored by the Employer and the

interpretationofDGAresultswillbeasperIEC-599.

2.6 RadioInterferenceandNoiseLevel

2.6.1 The transformers shall be designed with particular attention to thesuppressionofmaximumharmonicvoltage,especially thethirdandfifthsoastominimiseinterferencewithcommunicationcircuit.

2.6.2 Thenoise levelof transformer,whenenergised at normalvoltageandfrequencywithfansandpumpsrunningshallnotexceed,whenmeasuredunder standard conditions, the values specified in NEMA standard

publicationTR-1.

2.7 ThetransformersshallbecapableofbeingloadedinaccordancewithIS:6600/IEC-354.There shall be no limitation imposed by bushings, tapchangersetc.oranyotherassociatedequipment.

2.8 The transformer and all its accessories including CTs etc. shall bedesignedtowithstandwithoutinjury,thethermalandmechanicaleffectsofanyexternalshortcircuittoearthandofshortcircuitsattheterminalsofanywindingforaperiodof3secs.TheshortcircuitleveloftheHV&IVSystemtowhichthesubjecttransformerswillbeconnectedis40kA(sym,

rms,3phasefaulton400kV&220kV)&31.5kA(sym,rms,3phasefaulton132kV).



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2.9 Transformer shall be capable of withstanding thermal and mechanicalstressescausedbysymmetricalorasymmetricalfaultsonanywinding.

2.10 Transformersshallwithstand,withoutinjuriousheating,combinedvoltage

and frequency fluctuations which produce the following over fluxingconditions:

i) 125%for1-minute140%for5-seconds

ii) Biddershallindicate150%and170%overvoltagewithstandtime.

2.11 TheaircorereactanceofHVwindingoftransformershallnotbelessthan20%.

2.12 TertiaryWindings(forautotransformersabove100MVA)

2.12.1 The tertiary windings shall be suitable for connection of reactors orcapacitorswhichwouldbesubjectedtofrequentswitching.Allthewindingsshallbecapableofwithstandingthesestressesthatmaybecausedbysuchswitching.

2.12.2 The Tertiary winding shall be designed to withstand mechanical and

thermalstressesduetodeadshortcircuitonitsterminals.

2.12.3 Thetertiarywindingshallbesuitableforconnection toLTTransformerfor

auxiliarysupply.

3 ConstructionDetails

Thefeaturesandconstructiondetailsofeachpowertransformershallbeinaccordancewiththerequirementstatedhereunder.

3.1 TankandTankAccessories

3.1.1 Tank

3.1.1.1 Tankshallpreferablybeofweldedconstructionandfabricatedfromtestedqualitylowcarbonsteelofadequatethickness.

3.1.1.2 All seams and those joints not required to beopenedat site shall befactorywelded,andwhereverpossibletheyshallbedoublewelded.Aftercompletionoftankandbeforepainting,dyepenetrationtestshallbecarriedoutonweldedpartsofjackingbosses,liftinglugsandallloadbearing members. The requirement of post weld heat treatment oftank/stressrelievingshallbebasedonrecommendationofBS-5500table4.4.3.1.

3.1.1.3Tankstiffenersshall beprovided forgeneral rigidityandtheseshall be

designedtopreventretentionofwater.



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3.1.1.4 Thetransformershallbeofbelltypetankwiththejointatabout500mmabove the bottomof the tank. In case the joint is welded it shall beprovidedwith flangessuitable forrepeatedwelding. The jointshall beprovidedwithasuitablegaskettopreventweldsplatterinsidethetank.Propertankshieldingshallbedonetopreventexcessivetemperaturerise

ofthejoint.

3.1.1.5 Eachtankshallbeprovidedwith:

(a) Liftinglugssuitableforliftingtheequipmentcompletewithoil.

(b) Aminimumoffourjackingpadsinaccessiblepositiontoenablethetransformercompletewithoiltoberaisedorloweredusinghydraulicjacks.

(c) Suitablehaulageholesshallbeprovided.

3.1.1.6 Thetankshallbedesignedinsuchawaythatitcanbemountedontheplinthdirectly.

3.1.1.7Thebaseofeachtankshallbesodesignedthatitshallbepossibletomove thecompletetransformerunit byskidding inanydirectionwithoutinjurywhenusingplatesorrails.

3.1.2 TankCover

3.1.2.1 The tank cover shall preferably be sloped to prevent retention of rain

waterandshallnotdistortwhenlifted.

3.1.2.2 Atleasttwoadequatelysizedinspectionopeningsoneateachendofthetank, shall be provided for easy access to bushings and earthconnections. The inspection covers shall not weighmore than 25 kg.Handlesshallbeprovidedontheinspectioncovertofacilitatelifting.

3.1.2.3 The tank covers shall be fitted with pockets at the position of maximumoiltemperatureatmaximumcontinuousratingforbulbsofoilandwindingtemperatureindicators.Itshallbepossibletoremovethesebulbswithoutloweringtheoilinthetank.Thethermometershallbefitted

withacaptivescrewtopreventtheingressofwater.

3.1.2.4 Bushingturrets,coversof inspectionopenings,thermometerpocketsetc.shallbedesignedtopreventingressofwaterintoorleakageofoilfromthetank.

3.1.2.5 Allboltedconnectionsshallbefittedwithweatherproof,hotoilresistant,resilient gasket in between for complete oil tightness. If gasket iscompressible,metallicstops/othersuitablemeansshallbeprovidedtopreventover-compression.

3.1.3 AxlesandWheels



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3.1.3.1 Thetransformershallbemountedeitheronrollersoronconcreteplinthfoundationdirectly,aspermanufacturer'sstandardpractice.

3.1.3.2 The roller mounted transformers are to be provided with flanged bi-directional wheels and axles. This set ofwheels and axles shall be

suitableforfixingtotheundercarriageoftransformertofacilitateitsmovement on rail track. Suitable locking arrangement along withfoundationboltsshallbeprovidedforthewheelstopreventaccidentalmovementoftransformer.

3.1.3.3 Therailtrackgaugeshallbe1676mm.

3.1.3.4 Biddercansupplyonesetof trolleysinplaceofwheelassemblyrollersfor movement of transformer per sub-station for plinth mountedtransformer.

3.1.4 FoundationandAntiEarthquakeClampingDevice

3.1.4.1Toprevent transformer movement during earthquake, suitable clampingdevicesshallbeprovidedforfixingthetransformertothefoundation.

3.1.5 Conservator&OilPreservationSystem

3.1.5.1 Mainconservatorshallhaveaircelltypeconstantoilpressuresystemtopreventoxidationandcontaminationofoilduetocontactwithmoisture,andshallbefittedwithmagneticoillevelgaugewithlowoillevelpotentialfreecontacts.

3.1.5.2 OLTCshall haveconventional typeconservatorwithprismatic oil levelgauge.

3.1.5.3 Conservatortank

3.1.5.3.1Conservatortankshallhaveadequatecapacitywithhighestandlowestvisible-levels to meet the requirements of expansion of total cold oilvolumeinthetransformerandcoolingequipmentfromminimumambienttemperatureto100C.

3.1.5.3.2Theconservatorshallbefittedinsuchapositionsothatitcanberemoved for cleaning purposes. Suitable provision shall be kept toreplaceaircell,whereverapplicable.

3.1.5.3.3 Conservator shall be positioned so as not to obstruct any electricalconnectiontotransformer.

3.1.5.4 OilPreservationEquipment

Therequirementsofaircelltypeoilsealingsystemaregivenbelow.

3.1.5.4.1Contactoftheoilwithatmosphereisprohibitedbyusingaflexibleaircellofnitrilerubberreinforcedwithnyloncloth.



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3.1.5.4.2Thetemperatureofoilis likelytoriseupto100Cduringoperation.Assuchaircellusedshallbesuitableforoperatingcontinuouslyat100C.

3.1.5.4.3Aircellofconservatorshallbeabletowithstandthevacuumduring

installation/maintenanceperiods. Otherwiseprovision shall be kept toisolatetheconservatorfromthemaintankwhenthelatterisundervacuumbyprovidingavacuumsealingvalveorothersuitablemeansinthepipeconnectingmaintankwiththeconservator.

3.1.5.4.4Theconnectionofaircelltothetopoftheconservatorisbyairproofsealpreventingentranceofairintotheconservator.

3.1.5.5 DehydratingFilterBreather

Conservatorshallbefittedwithadehydratingfilterbreather.Itshallbeso

designedthat:

a) Passageofairisthroughsilicagel.

b) Silicagelisisolatedfromatmospherebyanoilseal.

c) Moistureabsorptionindicatedbya changeincolourofthetintedcrystals canbeeasilyobservedfromadistance.

d) Breatherismountednotmorethan1200mmaboverailtoplevel.

e) Tominimisetheingressofmoisturefollowingshallbeprovided.

i. Three breathers (of identical size) shall be connected inseriesformaintankconservator.

ii. Twobreathers(eachof2.5litresminimumvolume)shallbeconnectedinseriesforOLTCtankconservator.

3.1.6 PressureReliefDevice

Adequatenumberofpressure reliefdevicesshallbeprovidedatsuitablelocations.Theseshallbeofsufficientsizeforrapidreleaseofanypressure

thatmaybegeneratedinthetankandwhichmayresultindamagetoequipment. Thedevice shall operate at astatic pressure less than thehydraulictestpressureofthetransformertank.Itshallbemounteddirectlyonthetank.Onesetofelectricallyinsulatedcontactsshallbeprovidedforalarm/tripping..Dischargeofpressurereliefdeviceshallbeproperlytakenthroughpipesanddirectedawayfromthetransformer/otherequipmentandthisshallbepreventedfromsprayingonthetank.FollowingroutinetestsshallbeconductedonPRD

a. Airpressuretestb. Liquidpressuretest

c. Leakagetestd. Contacttest



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e. Dielectrictest.

3.1.7 BuchholzRelay

A double float/reed type Buchholz relay shall be provided. Any gas

evolvedin the transformer shall collectin thisrelay. The relay shall beprovided with a test cock suitable for a flexible pipe connection forcheckingitsoperationand takinggassample. Acopper/stainlesssteeltubeshall beconnectedfromthegas collector toa valve locatedabout1200mmabovegroundleveltofacilitatesamplingwiththetransformerinservice. Thedevice shall be provided with twoelectrically independentungroundedcontacts,oneforalarmongasaccumulationandtheotherfortrippingonsuddenriseofpressure.

3.1.8 TemperatureIndicators

3.1.8.1 OilTemperatureIndicator(OTI)

Alltransformersshallbeprovidedwitha150mmdialtypethermometerfortop oil temperature indication. The thermometer shall have adjustable,electrically independent ungrounded alarmand trip contacts, maximumreading pointer and resetting device shall be provided in the OTI. Atemperaturesensingelementsuitablylocatedinapocketontopoilshallbefurnished. This shall beconnectedto theOTIbymeansofcapillarytubing.Temperatureindicatordialsshallhavelineargradationstoclearly

readatleastevery2C.AccuracyclassofOTIshallbe1.5%orbetter.

3.1.8.2 WindingTemperatureIndicator(WTI)

Adeviceformeasuringthehotspottemperatureofeachwindingshallbeprovided(HV,IVandLV).Itshallcomprisethefollowing:

i) Temperaturesensingelement.

ii) Imagecoil.

iii) AuxiliaryCTs,ifrequiredtomatchtheimagecoil,shallbefurnishedand mountedinthecoolercontrolcabinet.

iv) 150 mm dia local indicating instrument with maximum readingpointer and two adjustable electrically independent, ungroundedcontacts; besides that required for control of cooling equipment ifany, one for high winding temperature alarm and one for trip.Temperatureindicatordialsshallhavelineargradationstoclearlyreadatleastevery2C.

v) Calibrationdevice.

vi) AccuracyclassofWTIshallbe1.5%orbetter.



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vii) Inadditiontotheabove,thefollowingequipmentshallbeprovidedfor remoteindicationofwindingtemperatureforeachofthewinding:

a) Signaltransmitterforeachwinding

Signal transmitter shall have additional facility to transmit signal forrecordingwindingtemperatureatEmployer'sdataacquisitionsystem,forwhichaduplexplatinumRTDwithnominalresistanceof100ohmsatzerodegree centigrade shall be supplied. The RTD shall be three wireungroundedsystem.ThecalibrationshallbeasperSAMA(USA)standardor equivalent. The RTD may be placed in the pocket containingtemperaturesensingelementandimagecoilforWTIsystemwhichwillbeusedforbothremoteWTIandDAS.NecessaryequipmentforsendingthesignaltoremoteWTIandDASshallbeprovided.Inlieu,separateRTDforeachofthefunctionsshallbeprovided.

b) Remotewindingtemperatureindicator

ItshallbesuitableforflushmountingonEmployer'spanel.ThisshallnotberepeaterdialoflocalWTIandwilloperatebysignaltransmitter.

Anyspecialcable required forshieldingpurpose, forconnectionbetweencoolercontrolcabinetandremoteWTIcontrolcircuit,shallbeinthescopeofContractor.OnlyoneRWTIwithafourpointselectorswitchshallbeprovidedforallthethreewindings(HV,IVandLV).

3.1.9 EarthingTerminals

3.1.9.1 Two(2)earthingpads(eachcompletewithtwo(2)nos.holes,M10bolts,plain and spring washers) suitable for connection to 75 x 12 mmgalvanisedsteelgroundingflatshallbeprovidedeachatpositionclosetoearthofthetwo(2)diagonallyoppositebottomcornersofthetank.

3.1.9.2 Twoearthingterminalssuitableforconnectionto75x12mmgalvanisedsteelflatshallalsobeprovidedoncooler,marshallingboxandanyotherequipmentmountedseparately.

3.2 Core

3.2.1 The coreshallbeconstructed fromhigh grade,non-ageing, cold rolled,supergrainoriented,siliconsteellaminations.

3.2.2 The design of the magnetic circuit shall be such as to avoid staticdischarges,developmentofshortcircuitpathswithinitselfortotheearthedclampingstructureandproductionoffluxcomponentatrightanglestotheplaneoflaminationswhichmaycauselocalheating.

3.2.3 Theinsulationofcoretoboltsandcoretoclampplatesshallbeableto

withstandavoltageof2KV(rms)for1minute.



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3.2.4 Core and winding shall be capable of withstanding the shock duringtransport,installationandservice.Adequateprovisionshallbemadetoprevent movement of core and winding relative to tank during theseconditions.

3.2.5 All steel sectionsused for supportingthecoreshallbe thoroughlysandblastedaftercutting,drillingandwelding.

3.2.6 Each core lamination shall be insulated with a material that will notdeteriorateduetopressureandhotoil.

3.2.7 Thesupporting frameworkofthecoreshallbesodesignedastoavoidpresence of pockets which would prevent complete emptying of tankthroughdrainvalveorcausetrappingofairduringoilfilling.

3.2.8 Adequateliftinglugswillbeprovidedtoenablethecoreandwindingstobe

lifted.

3.3 Windings

3.3.1 TheContractorshallensurethatwindingsofall400kVclasstransformersaremadeindustproofandconditionedatmosphere.

3.3.2 Theconductorsshallbeofelectrolyticgradecopperfreefromscalesandburrs.

3.3.3 Theinsulationoftransformerwindingsandconnectionsshallbefreefrom

insulating compounds which are liable to soften, ooze out, shrink orcollapseand be non-catalytic and chemically inactive in transformer oilduringservice.

3.3.4 Coilassemblyand insulatingspacersshall besoarrangedastoensurefreecirculationofoilandtoreducethehotspotofthewinding.

3.3.5 Thecoilswouldbemadeup,shapedandbracedtoprovideforexpansionandcontractionduetotemperaturechanges.

3.3.6 The conductor shall be transposed at sufficient intervals in order to

minimize eddy currents and to equalise thedistribution of currents andtemperaturealongthewinding.

3.4 InsulatingOil

3.4.1 The insulating oil shall conform to all parameters specified below, whiletested at supplier's premises. No inhibitors shall be used in oil. Thecontractor shall furnish test certificates from the supplier against theiracceptancenormsasmentionedbelow,priortodespatchofoilfromrefinerytosite.

----------------------------------------------------------------------------------------------



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Sl. Characteristics Requirements MethodofTestNo.----------------------------------------------------------------------------------------------1. Appearance Theoilshall Arepresentative

beclearand sampleoftheoil

transparentand shallbeexaminedfreefromsusp- ina100mmthickendedmatteror layer,atambientsediment temperature.

2. Densityat 0.89gm/cm3 IS:144829.5C(max.)

3. Kinematic 27cSt IS:1448Viscocityat27C(Max.)

4. Interfacial 0.04N/m IS:6104tensionat27C(Min.)

5. Flashpoint 140C IS:1448Penskey-Marten(closed)(Min.)

6. Pourpoint -6C IS:1448(Max.)

7. Neutralization 0.03mgKOH/gm IS:335value(total Appendix-Aacidity)(Max.)

8. Corrosivesulph- Non-Corrosive IS:335ur(intermsof Appendix-Bclassificationofcopperstrip)

9. Electricstrength

(breakdownvoltage)(Min.)

(a) Newuntreated 30kV(rms)(if IS:6792oil thisvalueisnot

attainedtheoilshallbetreated)

(b) Aftertreatment 60kV(rms)

10. Dielectricdiss-ipationfactor 0.002 IS:6262

(tandelta)at90C(Max.)



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11. Resistivity IS:6103(Min.)(ohmcm)

(a) at90C 35x1012

(b) at27C 1500x1012

12. Oxidationstability

(a) Neutralization 0.40mgKOH/gmvalueafteroxidation(Max.)

(b) Totalsludgeafter 0.10percentbyoxidation(Max) weight

13. Presenceof Theoilshall IS:335Appendix-Doxidation notcontaininhibitor anti-oxidant

additives14. Watercontent

(Max.)

(i) Newuntreated 50ppm IS:2362oil

(ii) Aftertreatment 15ppm IS:1866

15. AgeingCharacter-isticsafter96hrsasperASTM-D1934/IS:12177withcatalyst(copper)

(a) Resistivity(Min)(ohmcm)

at27C 2.5x1012at90C 0.2x1012

(b) Tandeltaat90C(Max.) 0.2

(c) Totalacidity(Max.) 0.05mgKOH/gm

(d) Sludgecontentwt.(Max.) 0.05%(Byweight)

16. PCBcontent Lessthan2ppm



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3.4.2 Subsequentlyoilsamplesshallbedrawn

i) Priortofillinginmaintankatsiteandshallbetestedfor

1. BDV

2. Moisturecontent

TheacceptancenormsforaboveparametersshallbeasperCl.3.4.1above.

ii) Prior to energisation at site and shall be tested for followingproperties

&acceptancenorms:

1. BDV(kVrms) 60kV(min.)

2. Moisturecontent 15ppm(max.)

3. Tan-deltaat90C 0.05(max.)

4. Resistivityat90C 1x1012ohm-cm(min.)

5. InterfacialTension 0.03N/m(min.)

3.4.3 Atmanufacturer'sworksoilsampleshallbedrawnbeforeandafterheatruntestandshallbetestedforfollowing:

1) BDV 60kV(min.)

2) Moisturecontent 15ppm

3) Dissolvedgasanalysis:

SamplesforDGAshallbetakenfromsamplingdevicewithin24hourspriortocommencementoftemperaturerisetestandimmediatelyafterthistest.

TheacceptancenormswithreferencetovariousgasgenerationratesduringthetemperaturerisetestshallbeasperIS:10593(basedonIEC-599).

3.4.4 Sufficientquantityofoilnecessaryformaintainingrequiredoillevelintank,radiators,conservatoretctillcommissioningshallbesupplied.

3.5 TerminalArrangements

3.5.1 Bushings

3.5.1.1The electrical and mechanical characteristics of bushings shall be inaccordancewithIS:2099andIS:3347.



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3.5.1.2 Bushingforvoltageof420kV,245kV,145kVand52kVshallbeoftheoilfilledcondensertype.36kVbushingshallbesolidporcelainoroilcommunicating type. Mountingdimensionsof 420kV, 245 kV,145kVand 52 kV bushing shall be as per drawing No.0000-T-E-A-001.

Dimensionsof36kVbushingshallconformtoIS:3347Part-V.

3.5.1.3 Oil Filled condenser typebushing shall beprovidedwith at least thefollowingfittings.:

(a) Oillevelgauge.

(b) Oilfillingpluganddrainvalveifnothermeticallysealed.

(c) Tapforcapacitanceandtandeltatest.

3.5.1.4 Where current transformers are specified, the bushings shall beremovablewithoutdisturbingthecurrenttransformers.

3.5.1.5 Bushingsofidenticalratingshallbeinterchangeable.

3.5.1.6 Porcelainusedinbushingmanufactureshallbehomogenous,freefromlamination,cavitiesandotherflawsorimperfectionsthatmightaffectthemechanicalordielectricqualityandshallbethoroughlyvitrified,toughandimpervioustomoisture.

3.5.1.7 Clampsandfittingsshallbeofhotdipgalvanisedsteel.

3.5.1.8 Bushing turrets shall be provided with vent pipes, to route any gascollectionthroughtheBuchholzrelay.

3.5.1.9 Noarcinghornsshallbeprovidedonthebushings.

3.5.1.10Suitableinsulatingcap(preferablyofporcelain)shallbeprovidedontheterminalofBushingoftertiarywindingtoavoidaccidentalexternalshortcircuit.

3.6 TerminalMarking

TheterminalmarkingandtheirphysicalpositionshallbeasperIS:2026.

3.7 NeutralEarthingArrangement

3.7.1 Theneutralterminalofautotransformershallbebroughttothegroundlevelbyabrass/tinnedcoppergroundingbar,supportedfromthetankbyusingporcelaininsulators.Theendofthebrass/tinnedcopperbarshallbebroughttothebottomofthetank,ataconvenientpoint,formakingboltedconnectiontotwo(2)75x12mmgalvanisedsteelflatsconnectedtoEmployer'sgroundingmat.

3.8 CoolingEquipmentanditsControl



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3.8.1 CoolingEquipment

3.8.1.1 Thecoolershallbedesignedusing2x50%radiatorbanks. Designofcoolingsystemshallsatisfytheperformancerequirements.

3.8.1.2 Eachradiatorbankshall have itsown cooling fans,oilpumps,oil flowindicator,shutoffvalvesatthetopandbottom(80mmsize),liftinglugs,topandbottomoilfillingvalves,airreleaseplugatthetop,adrainandsamplingvalveandthermometerpocketfittedwithcaptivescrewcapontheinletandoutlet.

3.8.1.3 Requirednumberof standbyfansofapproximately20%capacityshallalsobeprovidedwitheachradiatorbank.

3.8.1.4 Cooling fansshallnotbedirectlymountedonradiatorbankwhichmay

causeunduevibration.Theseshallbelocatedsoastopreventingressof rainwater. Each fanshallbesuitablyprotectedbygalvanisedwireguard. The exhaust air flow from cooling fan shall not be directedtowardsthemaintankinanycase.

3.8.1.5 Two(2),100%centrifugaloraxialonlineoilpumps (outofwhichonepump shall be standby) shall be provided with each radiator bank.MeasuresshallbetakentopreventmaloperationofBuchholzrelaywhenalloilpumpsaresimultaneouslyputintoservice.Thepumpshallbesodesignedthatuponfailureofpowersupplytothepumpmotor,thepumpimpellerwillnotlimitthenaturalcirculationofoil.

3.8.1.6 Anoilflowindicatorshallbeprovidedfortheconfirmationoftheoilpumpoperatinginanormalstate.Anindicationshallbeprovidedintheflowindicatortoindicatereverseflowofoil/lossofoilflow.

3.8.1.7 Coolingfansandoilpumpmotorsshallbesuitableforoperationfrom415volts,threephase50HzpowersupplyandshallconformtoIS:325.Eachcoolingfanandoilpumpmotorsshallbeprovidedwithstarterthermaloverloadandshortcircuitprotection.Themotorwindinginsulationshallbeconventionalclass'B'type.MotorsshallhavehoseproofenclosureequivalenttoIP:55asperIS:4691.

3.8.1.8 Thecooleranditsaccessoriesshallpreferablybehotdipgalvanisedorcorrosionresistantpaintshouldbeappliedtoit.

3.8.1.9 Expansion joint shallbeprovided, oneeachon topandbottomcoolerpipeconnections.

3.8.1.10 Airreleasedeviceandoilplugshallbeprovidedonoilpipeconnections.Drainvalvesshallbeprovidedinorderthateachsectionofpipeworkcanbedrainedindependently.

3.8.2 CoolingEquipmentControl(ONAN/ONAF/OFAFCOOLING)



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3.8.2.1 Automatic operation control of fans/pumps shall be provided (withtemperature change) from contacts of winding temperature indicator.TheContractorshallrecommendthesettingofWTIforautomaticchangeover of cooler control fromONAN toONAFand then toOFAF. Thesettingshallbesuchthathuntingi.e.frequentstart-upoperationsfor

smalltemperaturedifferentialdonotoccur.

3.8.2.2 Suitablemanualcontrol facility for cooler fans and oil pumps shall beprovided.

3.8.2.3 Thechangeovertostandbyoilpumpincaseoffailureofserviceoilpumpshallbeautomatic.

3.8.2.4Selectorswitchesandpushbuttons,shallalsobeprovidedinthecoolercontrolcabinettodisconnecttheautomaticcontrolandstart/stopthefansandpumpmanually.

3.8.3 IndicatingDevices

Followinglampindicationsshallbeprovidedincoolercontrolcabinet:

a) ControlSupplyfailure.

b) Coolingfanfailureforeachbank.

c) Coolingpumpfailureforeachpump.

d) Nooilflow/reverseoilflowforpumps.

e) Commonthermaloverloadtrip.

Onepotentialfreeinitiatingcontactforalltheaboveconditionsshallbewiredindependentlytotheterminalblocksofcoolercontrolcabinet.

3.8.4 Valves

3.8.4.1 Allvalvesuptoandincluding100mmshall beofgunmetalorofcaststeel/castiron.Largervalvesmaybeofgunmetalormayhavecastironbodieswithgunmetalfittings.Theyshallbeoffullwaytypewithinternal

screwandshallopenwhenturnedcounterclockwisewhenfacingthehandwheel.

3.8.4.2 Suitablemeansshallbeprovidedforlockingthevalvesintheopenandclosepositions. Provisionisnotrequiredforlocking individualradiatorvalves.

3.8.4.3 Each valve shall be provided with the indicator to show clearly thepositionofthevalve.

3.8.4.4 Allvalvesflangesshallhavemachinedfaces.



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3.8.4.5 All valves in oil line shall be suitable for continuous operation withtransformeroilat100C.

3.8.4.6 Theoilsamplingpointformaintankshallhavetwoidenticalvalvestobeputinseries.Oilsamplingvalveshallhaveprovisiontofixrubberhoseof

10mmsizetofacilitateoilsampling.3.8.4.7 A valve or other suitable means shall be provided to fix the on line

dissolvedgasmonitoringsystemtofacilitatecontinuousdissolvedgasanalysis.Thelocation&sizeofthesameshallbefinalisedduringdetailengineeringstage.

3.8.4.8 Suitablevalvesshallbeprovided totakesampleofoilfrom theOLTCchamberduringoperationofthetransformer.

3.8.4.9 Aftertesting,insidesurfaceofallcastironvalvescomingincontactwithoilshallbeappliedwithonecoatofoilresistingpaint/varnishwithtwo

coatsof redoxide zincchromateprimer followedbytwo coats of fullyglossyfinishingpaintconforming toIS:2932andofashade(preferablyred or yellow) distinct and different from that of main tank surface.OutsidesurfaceexceptgasketsettingsurfaceofbutterflyvalvesshallbepaintedwithtwocoatsofredoxidezincchromateconformingtoIS:2074followedbytwocoatsoffullyglossyfinishingpaint.

3.8.4.10 Allhardwareusedshallbecadmiumplated/electrogalvanised.

3.9 TapChangingEquipment

3.9.1 TapChangeSwitchGeneralRequirement

OLTCshallbemotoroperatedforlocalaswellasremoteoperation.Anexternalhandleshallbeprovidedforlocalmanualoperation.Thishandleshallbesuitableforoperationbyamanstandingatgroundlevel.

3.9.2 OnLoadTapChangingGear(OLTC)

3.9.2.1 Each single/ three phase transformer shall be provided with voltagecontrol equipment of the tap changing type for varying its effectivetransformation ratio whilst the transformers are on load and without

producingphasedisplacement.

3.9.2.2 The requirements of on load tapchanging equipment are given herebelow:

a) The current diverting contacts shall be housed in a separate oilchamber not communicating with the oil in main tank of thetransformer.

b) Thecontactsshallbeaccessiblefor inspectionwithout loweringoillevelinthemaintankandthecontacttipsshallbereplaceable.



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c) TheBiddershallindicatethesafeguardsinordertoavoidharmfularcingatthecurrentdivertingcontactsintheeventofoperationoftheOLTCgearunderoverloadconditionsofthetransformer.NecessarytoolsandtacklesshallbefurnishedformaintenanceofOLTCgear.

d) The OLTC oil chamber shall have oil filling and drain plug, oilsamplingvalve,reliefventandlevelglass.Itshallalsobefittedwithaoilsurgerelaytheoutletofwhichshallbeconnectedtoaseparateconservatortank.

e) The diverter switch or arcing switch shall be designed so as toensurethat its operation once commenced shall be completedindependentlyofthecontrolrelaysorswitches,failureofancillarysupplies etc.To meet any contingency which may result inincompleteoperationofthediverterswitch,adequatemeansshallbeprovidedtosafeguardthetransformeranditsancillaryequipment.

f) Tapchangershallbesomountedthatbellcoveroftransformercanbelifted without removingconnectionsbetweenwindingsandtapchanger.

g) Local OLTC control cabinet shall be mounted on the tank inaccessible position. It should be adequately ventilated andprovidedwithanti-condensationmetalcladheaters.Allcontactorsrelaycoilsandotherpartsshallbeprotectedagainstcorrosion,deteriorationduetocondensation,fungietc.

h) Operatingmechanismforonloadtapchangershallbedesignedtogothroughonestepoftapchangepercommand.Subsequenttapchangesshallbeinitiatedonlybyaneworrepeatcommand.

i) On load tap changer shall be equipped with a time delayedINCOMPLETESTEPalarmconsistingofanormallyopencontactwhich closes, if the tap changer fails to make a complete tapchange.Thealarmshallnotoperateformomentarylossofauxiliarypower.

j) Theselsynunitsorapprovedequivalentsshallbe installedinthe

localOLTCcontrolcabinettoprovidetappositionindicationforthetransformer.TheBiddershallalsoprovideasetofinstrumentsfortap position indication in the control room. Complete mountingdetailsshallbeincludedintheapproveddiagram.

k) Transformer on load tap shall be equipped with a fixed resistornetworkcapableofprovidingdiscretevoltagestepsforinputtothesupervisorysystem.

l) Limit switches shall be provided to prevent overrunning of themechanismandshallbedirectlyconnectedinthecircuitofthe

operatingmotor.Inaddition,amechanicalstopshallbeprovidedtopreventover-runningofthemechanismunderanycondition.



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m) Limit switches may be connected in the control circuit of theoperating motor provided that a mechanical de-clutchingmechanismisincorporated.

n) Thermal device or othermeans shall be provided toprotect themotorandcontrolcircuit. All relays,switches, fusesetc. shallbemountedinthelocalOLTCcontrolcabinetandshallbeclearlymarkedforthepurposeofidentification.

o) Apermanently legible lubrication chart if required, shall be fittedwithinthelocalOLTCcontrolcabinet.

p) Any 'DROP DOWN' tanks associated with the tap changingapparatusshallbefittedwithguiderodtocontrolthemovementsduringliftingorlowering.

q) Afivedigitcountershallbefittedtothetapchangingequipmenttoindicatethenumberofoperationscompleted.

r) All relays and operating devices shall operate correctly at anyvoltagebetweenthelimitsspecified.

s) Itshallnotbepossibletooperatetheelectricdrivewhenthemanualoperatinggearisinuse.

t) Itshallnotbepossibleforanytwocontrolstobeinoperationatthe

sametime.

u) The equipment shall be suitable for supervisory control andindication with make before break multi-way switch, having onepotential freecontact foreach tapposition. This switch shall beprovided in addition to any other switch/switches which may berequiredforremotetappositionindication.

v) Operationfromthe localorremotecontrolswitchshallcauseonetap movement only until thecontrol switch is returned to the offpositionbetweensuccessiveoperation.

w) Allelectricalcontrolswitchesandthelocaloperatinggearshallbeclearlylabelledinasuitablemannertoindicatethedirectionoftapchanging.

x) TransferofsourceintheeventoffailureofoneACsupplyshallnotaffectthetapchanger.

3.9.3 OLTCControlofThreePhaseTransformers

Eachthreephasetransformershallbesuitableforlocalandremote

control.Thecontrolfeatureshallprovidethefollowing:



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3.9.3.1 LocalElectricalControl

(a) 'Local-remote' selector switch mounted in the local OLTC controlcabinetshallswitchcontrolofallloadtapchangersasfollowings:

i) Whentheselectorswitchisin'local'position,itshallbepossibletooperatethe'raise-lower'controlswitchesspecified inclause3.9.3.1(b) below. Remote control of the raise-lower functionsshallbeprevented.

ii) Whentheselectorswitchisin'remote'positionthelocalOLTCcontrolcabinetmounted'raise-lower'switchspecifiedinclause3.9.3.1(b) belowshall be in-operative. Remote control of theraise/lowerfunctionshallbepossiblefromtheremotecontrolpanel.The'local-remote'selectorswitchshallhaveatleasttwo

spare contacts per position which are closed in thatpositionbutopenintheotherposition.

(b) A'raise-lower'controlswitch/pushbuttonshallbeprovidedinthelocalOLTCcontrolcabinet.Thisswitchshallbeoperativeonlywhen'local

remote'selectorswitchisin'local'position.

(c) AnOFF-ONtapchangercontrolswitchshallbeprovidedinthelocalOLTCcontrolcabinetofthetransformer.Thetapchangershallbein-operativeintheOFFposition.AlsotheOFF-ONswitchshallhaveatleastonesparecontactperpositionwhichisclosedinthatposition

butopenintheotherposition.

3.9.3.2 ManualControl

ThecrankingdeviceformanualoperationoftheOLTCgearshallberemovableandsuitableforoperationbyamanstandingatgroundlevel.Themechanismshallbecompletewiththefollowing:

a) Mechanicaltappositionindicatorwhichshallbeclearlyvisiblefromnear thetransformer.

b) Amechanicaloperationcounter.

c) Mechanical stops to prevent over-cranking of the mechanismbeyondthe extremetappositions.

d) Themanualcontrol considered as backup tothemotor operatedloadtapchangercontrolshallbeinterlockedwiththemotortoblockmotor start-up during manual operation. The manual operatingmechanismshallbelabelledtoshowthedirectionofoperationforraisingtheHVterminalvoltageandvice-versa.

3.9.3.3 RemoteElectricalGroupControl



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TheOLTCcontrolschemeofferedshallhaveprovisionofremoteelectricalgroup control during the parallel operation of transformer. This is inadditiontoindependentcontrolofOLTC:

i) AfourpositionselectorswitchhavingMaster,Follower,Independent

andOffpositionshallbeprovidedintheremoteOLTCcontrolpanelforeachtransformer.ThisshallbewiredtoenableoperatortoselectoperationofOLTCineitherMaster,FollowerorIndependentmode.

ii) Outofsteprelayswithtimercontactsshallalsobeprovidedtogivealarmandindicationincasetappositioninallthetransformersundergroupcontrolarenotinsameposition.

iii) MasterPosition

If the selector switch is inMasterposition, it shall bepossible to

controltheOLTCunitsinthefollowermodebyoperatingthecontrolsof the master unit. Independent operation of the units underFollowermodeshallhavetobeprevented.Howevertheunitsunderindependentmodewillbecontrolledindependently.

iv) FollowerPosition

IftheselectorswitchisinFollowermode,controlofOLTCshallbepossibleonlyfrompaneloftheMasterunit.

v) IndependentPosition

InthispositionofSelectorSwitch,ControlofOLTCofindividualunitshallonlybepossible.

3.9.4 OLTCControlofsinglephaseTransformer

ForthreesinglephaseunitsoperatingasthreephasebanktheOLTCgearshallbesuitableforlocalandremotecontrol.Thecontrolfeaturesshallprovidethefollowing:

i) LocalElectricalControl

a) 'Local-remote'selectorswitchmountedinthelocalOLTCcontrolcabinetshallswitchcontrolofallonloadtapchangersasunder:

Whentheselectorswitchisin'local'position,itshallbepossibletooperateanyofthe'raise-lower'controlswitchesspecifiedinsection(iii)and(iv)below.

Controloftheraise-lowerfunctionfromthecontrolpanelshallbeprevented.

When the selector switch is 'remote' position the raise-lowerfunctionsformswitches in localOLTCcontrolcabinetsaswell as



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cooler control cabinet specified in Section (iii) and (iv) shall beinoperative.Remotecontroloftheraise-lowerfunctionofthethreephasetransformerbanksshallbepossiblefromthecontrolpanel.

Theremote-localselectorswitchshallbehaveatleasttwospare

contactsperposition.

b) 'Independent-combined selector switch shall be provided forsinglephasetransformeronlyandshallbemountedinthecoolercontrolcabinet.Thisswitchshallcontroltheonloadtapchangersasfollows.

Whentheselectorswitchincombinedposition,itshallbepossibletoraise-lowertapsbyoperatingthecombined'raise-lower'switchincoolercontrolcabinetortheremoteraise-lowerswitch.Independentoperationofeachsinglephasetransformerwillbeprevented.

When the selector switch is in independent position it shall bepossible to raise-lowertapsby operating individuallyeach singlephase transformer through their individual 'raise-lower' controlswitch mounted in Local OLTC Control Cabinet. Combinedoperation of all the three (3) single phase transformers will beprevented.

c) Acombined raise-lower control switchshall beprovided in thecooler control cabinet for a bank of three single phasetransformers only. This switch shall be functional only when

'local-remote'selectorswitchisinlocalpositionand'Independentcombined'selectorswitchisincombinedposition.

d) An individual 'raise-lower'controlcabinet foreachsinglephasetransformer. This switch shall be functional only when 'local-remote' selector switch is in local position and 'individual-combined'selectorswitchisinindividualposition.

ii) LocalManualcontrol

The cranking device for manual operation for OLTC gear shall beremovableandsuitableforoperationbyamanstandingatgroundlevel.

Themechanismshallbecompletewiththefollowing.

a) Mechanicaltappositionindicatorwhichshallbeclearlyvisiblefromnearthetransformer.

b) Amechanicaloperationcounter.c) Mechanical stops to prevent over-crankingof themechanismbeyond

theextremetappositions.d) Themanualcontrol consideredasback upto themotor operatedon

loadtapchargercontrolshallbeinterlockedwiththemotortoblockmotor start-up during manual operation. The manual operatingmechanism shall be labelled to show the direction of operation for

raisingthevoltageandvice-versa.iii) RemoteElectricalGroupControl



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The remoteOLTCschemeofferedshall haveprovisionto raiseor lowertaps only for the complete bank of three single phase transformers.Individual single phase OLTC operation shall not be possible from theremotecontrolpanel.

TheOLTCcontrolschemeshallhaveprovisionofremoteelectricalgroupcontrolwhenthethreephasebankisinparalleloperationwiththreephasetransformers/threephasebanksofsinglephasetransformers.

a) A four positionselector switch havingMaster, Follower, IndependentandOffpositionshallbeprovidedintheremoteOLTCcontrolpanelforthree(3)phasebankofsinglephasetransformers.Thisshallbewiredtoenable the operator to select operation of OLTC in either Master,FollowerorIndependentmode.

b) Out of step relayswith timercontacts shall alsobeprovided to givealarmandindicationincasetapsofalthetransformersundercontrolarenotinsameposition.

c) MasterPosition

Iftheselectorswitchisinmasterposition,itshallbepossibletocontroltheOLTCunitsofothertransformerbanks/threephasetransformerinthefollowermadebyoperationthemasterunit.

d) FollowerPosition

IftheselectorswitchisinFollowerpositioncontrolofOLTCshallbepossibleonlyfrompanelwheremastermodeisselected.

e) IndependentPosition

Inindependentpositionofselectorswitch,controlofOLTCshallbepossibleonlyfromthepanelwhereindependentmodeisselected.

3.9.5 Thecontrolcircuitsshallcomplywithfollowingconditions:

3.9.5.1 Aninterlocktocutoffelectricalcontrolautomaticallyuponrecoursebeingtakentothemanualcontrolinemergency.

3.9.5.2 Reinforcement of the initiating impulse for a tap change, ensuring apositivecompletiononceinitiatedtothenext(higherorlower)tap.

3.9.5.3 "Step-by-Step" operation ensuringonly one tap change from each tapchangingimpulseandalock-outofthemechanismifthecontrolswitch(orpushbutton)remainsinthe"operate"position.

3.9.5.4 Aninterlocktocut-outelectricalcontrolwhenittendstooperatethegear

beyondeitheroftheextremetappositions.



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3.9.5.5 Anelectricalinterlocktocut-offacounterimpulseforreversestepchangebeing initiatedduringaprogressingtapchangeanduntil themechanismcomestorestandresetscircuitsforafreshposition.

3.9.5.6 Tap change in progress indication shall be provided by means of an

indicatinglampat theEmployer'scontrolpanel. Necessarycontacts forthisandforremotetappositionindicatoratEmployer'scontrolpanelshallbeprovidedbytheBidder.

3.9.5.7 Protective apparatus, considered essential by the Bidder according tospecialitiesofthegear.

3.10 LocalOLTCControlCabinet,CoolerControlCabinetand RemoteTapChangerControlPanel

3.10.1 Eachsingle/threephasetransformerunitshallbeprovidedwithlocalOLTC

controlcabinet,coolercontrolcabinetandRTCCpanel.

3.10.2 The sheet steel used for cooler controlcabinet and local OLTCcontrolcabinetshallbeatleast2.5mmthick.ThedegreeofprotectionshallbeIP:55 in accordance with IS:13947. The gaskets used shall be ofneoprenerubber.Alltheseparatelymountedcabinetsandpanelsshallbefreestandingfloormountedtypeandhavedomedorslopingroof.Allthecontrolcabinetsshallbeprovidedwithsuitableliftingarrangement.

3.10.3 Aspaceheater,andcubiclelightingwithON-OFFswitchshallbeprovidedineachpanel.

3.10.4 Necessaryshortingofterminalsshallbedoneatthecoolercontrolcabinet,local OLTC cabinet and remote OLTC panel. All the CT secondaryterminals in the cooler control cabinet shall have provision for shortcircuitingtoavoidCTopencircuitwhileitisnotinuse.

3.10.5 CoolerControlCabinet

3.10.5.1 Thecoolercontrolcabinetshall haveall necessarydevicesmeant forcoolercontrolandlocaltemp.indicators.AllthecontactsofvariousprotectivedevicesmountedonthetransformerandallthesecondaryterminalsofthebushingCTsshallalsobewireduptotheterminalboard

in the cooler controlcabinet. All thenecessary terminals for remoteconnectiontoEmployer'spanelshallbewireduptothecoolercontrolcabinet.

3.10.5.2 Thecoolercontrolcabinetshallhavetwo(2)sections.Onesectionshallhavethecontrolequipmentexclusivelymeant forcoolercontrol. Theothersectionshallhousethetemperatureindicators,aux.CTsandtheterminalboardsmeantforterminationofvariousalarmandtripcontactsaswellasvariousbushingCTsecondary.AlternativelythetwosectionsmaybeprovidedastwoseparatepanelsdependingonthestandardpracticeoftheBidder.



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3.10.5.3 Thetemperatureindicatorsshallbesomountedthatthedialsareabout1200mm fromground level. Glazed door of suitable size shall beprovidedforconvenienceofreading.

3.10.5.4 Deleted.

3.10.6 LocalOLTCControlCabinet

The Local OLTC control cabinet shall house all necessary devicesmeantforOLTCcontrolandindication.Itshallbecompletewiththefollowing:

I) A circuit breaker/contactor with thermal overload devices forcontrolling theACAuxiliarysupplytotheOLTCmotor.

ii) Cubiclelightwithdoorswitch.

iii) Spaceheaterstopreventcondensationofmoisture.

iv) Padlockingarrangementforhingeddoorofcabinet.

v) CableterminalglandsforpowerandcontrolcablestotheOLTCgear.

3.10.7 RemoteTapChangerControlPanel.

3.10.7.1 TheContractor shall supply a Remote TapChanger Control (RTCC)

panelsuitableforremoteoperationofOnloadtapchanginggear.

3.10.7.2 TheRTCCpanelshallhouseactuatingswitchforelectricalraise/lowercontrol,tappositionindicator,signallampsfor"Tapchangeinprogress"and"Tapchangeroutofstep",andallotherauxiliarydevicesforremoteelectricalcontroloftheOLTC.Fortappositionindicator,thedualoutputtypeOLTCtransducershallbeprovidedintheRTCCpanel.TheoneoftheoutputofthistransducershallbeusedforlocalindicationoftappositioninRTCCpanelandotheroutput(0-10mAor4-20mAshallbeusedforRTUs.

3.10.7.3TheRTCCpanelshallbelocatedinEmployer'scontrolroom.Thesize&colouroftheRTCCpanelshallmatchwithEmployer'scontrolpanel.Thematchingdetailsshallbefurnishedatthetimeofaward.

3.11 AuxiliaryPowerSupplyofOLTC,CoolerControlandPowerCircuit

3.11.1 Twoauxiliarypowersupplies,415volt, threephasefour(4)wireshallbeprovidedbytheEmployeratcoolercontrolcabinetforOLTCandcoolercontrolandpowercircuit.

3.11.2 All loads shall be fed byone of the two feeders through anelectrically

interlockedautomatictransferswitchhousedinthecoolercontrolcabinetforonloadtapchangercontrolandcoolercircuits.



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Designfeaturesofthetransferswitchshallincludethefollowing:

a) Provisionfortheselectionofoneofthefeederasnormalsourceandotherasstandby.

b) Uponfailureofthenormal source, the loads shall beautomaticallytransferredafteranadjustabletimedelaytostandbysources.

c) Indicationtobeprovidedatcoolercontrolcabinetforfailureofnormalsource and for transfer to standby source and also for failure totransfer.

d) Automatic re-transfer tonormalsourcewithout anyintentional timedelayfollowingre-energizationofthenormalsource.

e) Boththetransferandthere-transfersshallbedeadtransfersandACfeedersshallnotbeparalleledatanytime.

3.11.3 PowerSupplyforOLTCCircuits

a) ACfeedershallbebroughttothelocalOLTCcontrolcabinetbytheContractoraftersuitableselectionatcoolercontrolcabinetforwhichdescriptionisgivenin3.11.2above,forcontrolpowercircuitofOLTC.

b) TheContractorshallderiveACpowerforOLTCcontrolcircuitryfromtheACfeederasmentionedabovebyusingappropriatelyrateddry

typetransformers.IfthecontrolcircuitisoperatedbyDCsupply,thensuitable main and standby converters shall be provided by theContractortobeoperatedfromACpowersource.

3.11.4 PowerSupplyforCoolerCircuits

3.11.4.1ControlandpowersuppliesaretobegivenforCoolercircuitsaftertheselectionasmentionedin3.11.2above.

3.11.4.2TheContractorshallderiveACpowerforCoolerControlCircuitryfromtheACfeederas mentionedabovebyusingappropriately rated dry type

transformer.IfthecontrolcircuitisoperatedbyDCsupplythensuitablemainandstandbyconvertorsshallbeprovidedbytheContractor,tobeoperatedfromACpowersource.

3.11.5 Necessary isolating switches and HRC fuses shall be provided atsuitablepointsasperEmployer'sapprovedscheme.

4 Fittings

4.1 The following fittings shall be provided with each three phasetransformercoveredinthisspecification:



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4.1.1 Conservatorformaintankwithoilfillingholeandcap,isolatingvalves,drainvalve,magneticoillevelgaugewithlowlevelalarmcontactsanddehydratingbreather..

4.1.2 ConservatorforOLTCwithdrainvalve,oilsurgeRelay,fillingholewith

cap,prismaticoillevelgaugeandsilicagelbreather.

4.1.3 Oilpreservationequipment.

4.1.4 Pressurereliefdeviceswithalarm/tripcontacts.

4.1.5 Buchholz relay double float/reed type with isolating valves on bothsides,bleedingpipewithpetcockattheendtocollectgasesandalarmandtripcontacts.

4.1.6 Airreleaseplug.

4.1.7 Inspectionopeningsandcovers.

4.1.8 Bushing with metal parts and gaskets to suit the terminationarrangement.

4.1.9 Winding temperature indicators for local and remotemounting. Oneremotewindingtemperatureindicatorwithafourpointselectorswitchshallbeprovidedforthethreewindingsforthreephaseunittohaveselectionofanyofthethreewindings.

4.1.10 Cover liftingeyes, transformer liftinglugs, jackingpads, towingholesandcoreandwindingliftinglugs.

4.1.11 Protectedtypemercuryoralcoholinglassthermometer.

4.1.12 Bottom and top filter valves with threaded male adaptors, bottomsamplingvalveanddrainvalve.

4.1.13 Ratinganddiagramplatesontransformersandauxiliaryapparatus.

4.1.14 Flangedbi-directionalwheels/Trolleyformovement

4.1.15 Coolercontrolcabinet.

4.1.16 Onloadtapchanginggear.

4.1.17 Coolingequipment.

4.1.18 Bushingcurrenttransformers.

4.1.19 Oilflowindicator.

4.1.20 Drainvalves/plugsshallbeprovidedinorderthateachsectionofpipeworkcanbedrainedindependently.



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4.1.21 Terminalmarkingplates.

4.1.22 Valvesscheduleplates.

4.2 The fittings listed above are only indicative and other fittings whichgenerallyare required forsatisfactoryoperationof thetransformeraredeemedtobeincluded.

5 InspectionandTesting

TheContractorshallcarryoutacomprehensiveinspectionandtestingprogramme duringmanufacture of the equipment. An indication ofinspectionenvisagedbytheEmployerisgivenunderClause5.1.Thisishowevernot intended to formacomprehensiveprogrammeasit isContractor'sresponsibilitytodrawupandcarryoutsuchaprogrammein

the form of detailed quality plan duly approved by Employer fornecessaryimplementation.

5.1 Inspection

5.1.1 TankandConservator

5.1.1.1 Certificationofchemicalanalysisandmaterialtestsofplates.

5.1.1.2 Checkforflatness.

5.1.1.3 Electricalinterconnectionof top and bottombybraidedtinnedcopperflexible.

5.1.1.4 Welder'squalificationandweldprocedure.

5.1.1.5 Testingofelectrodesforqualityofbasematerialsandcoatings.

5.1.1.6 Inspectionofmajorweldpreparation.

5.1.1.7 Crackdetectionofmajorstrengthweldseamsbydyepenetrationtest.

5.1.1.8 Measurementoffilmthicknessof:

i) Oilinsolublevarnish.

ii) Zincchromatepaint.

iii) Finishedcoat.

5.1.1.9 Check correct dimensions between wheels, demonstrate turning ofwheelsthrough90Candfurtherdimensionalcheck.



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5.1.1.10Checkforphysicalpropertiesofmaterialsforliftinglugs,jackingpads,etc.AllloadbearingweldsincludingliftinglugweldsshallbesubjectedtoNDT.

5.1.1.11Leakagetestoftheconservator.

5.1.1.12Certificationofalltestresults.

5.1.2 Core

5.1.2.1 Sample testing of core materials for checking specific loss, bendproperties,magnetisationcharacteristicsandthickness.

5.1.2.2 Checkonthequalityofvarnishifusedonthestampings:

i) Measurementofthicknessandhardnessofvarnishonstampings.

ii) Solventresistancetesttocheckthatvarnishdoesnotreactinhotoil.

iii) Checkoverallqualityofvarnishbysamplingtoensureuniformshining colour, no bare spots, no over burnt varnish layer and nobubblesonvarnishedsurface.

5.1.2.3 Checkontheamountofburrs.

5.1.2.4 Bowcheckonstampings.

5.1.2.5 Checkfortheoverlappingofstampings.Cornersofthesheetaretobepart.

5.1.2.6 Visualanddimensionalcheckduringassemblystage.

5.1.2.7 Checkforinterlaminarinsulationbetweencoresectorsbeforeandafterpressing.

5.1.2.8 Checkoncompletedcore formeasurementofiron lossandcheck foranyhotspotbyexcitingthecoresoastoinducethedesignedvalueof

fluxdensityinthecore.

5.1.2.9 Visualanddimensionalchecksforstraightnessandroundnessofcore,thicknessoflimbsandsuitabilityofclamps.

5.1.2.10 Highvoltagetest(2kVforoneminute)betweencoreandclamps.

5.1.2.11 Certificationofalltestresults.

5.1.3 InsulationMaterial

5.1.3.1. Samplecheckforphysicalpropertiesofmaterials.



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5.1.3.2 Checkfordielectricstrength.

5.1.3.3 Visualanddimensionalchecks.

5.1.3.4 Checkforthereactionofhotoiloninsulatingmaterials.

5.1.3.5 Dimensionstabilitytestathightemperatureforinsulatingmaterial.

5.1.3.6 Trackingresistancetestoninsulatingmaterial


5.1.4 Winding

5.1.4.1 Sample check on winding conductor for mechanical properties andelectricalconductivity.

5.1.4.2 Visualanddimensionalchecksonconductorforscratches,dentmarksetc.

5.1.4.3 SamplecheckoninsulatingpaperforpHvalue,burstingstrengthandelectricstrength.

5.1.4.4 Checkforthereactionofhotoiloninsulatingpaper.

5.1.4.5 Checkforthebondingoftheinsulatingpaperwithconductor.

5.1.4.6 Check and ensure that physical condition of all materials taken forwindingsissatisfactoryandfreeofdust.

5.1.4.7 Checkforabsenceofshortcircuitbetweenparallelstrands.

5.1.4.8 Checkforbrazedjointswhereverapplicable.

5.1.4.9 Measurement of voltage ratio to be carried out when core/yoke iscompletelyrestackedandallconnectionsareready.

5.1.4.10 Conductorenameltestforcheckingofcracks,leakageandpinholes.

5.1.4.11 Conductorflexibilitytest

5.1.4.12Heatshrinktestforenamelledwire.


5.1.5 ChecksBeforeDryingProcess

5.1.5.1 Check condition of insulation on the conductor and between thewindings.



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5.1.5.2 Check insulationdistancebetween highvoltage connections, cablesandearthandotherliveparts.

5.1.5.3 Checkinsulatingdistancesbetweenlowvoltageconnectionsandearthandotherparts.

5.1.5.4 Insulationofcoreshallbetestedat2kV/minutebetweencoretoboltsandcoretoclampplates.

5.1.5.5 Checkforpropercleanlinessandabsenceofdustetc.


5.1.6 ChecksDuringDryingProcess

5.1.6.1 Measurementand recording of temperature, vacuumanddrying time

duringvacuumtreatment.

5.1.6.2 CheckforcompletenessofdryingbyperiodicmonitoringofIRandTandelta.


5.1.7 AssembledTransformer

5.1.7.1 Check completed transformer against approved outline drawings,provisionforallfittings,finishleveletc.

5.1.7.2 Testtocheckeffectiveshieldingofthetank.

5.1.7.3 Jackingtestwithoilonalltheassembledtransformers.

5.1.7.4 Dyepenetrationtestshallbecarriedoutafterthejackingtest.

5.1.8 BoughtOutItems

5.1.8.1 ThemakesofallmajorboughtoutitemsshallbesubjecttoEmployer'sapproval.

5.1.8.2 The Contractor shall also prepare a comprehensive inspection andtestingprogramme for all bought out/sub-contracted items and shallsubmitthesametotheEmployerforapproval.Suchprogrammeshallincludethefollowingcomponents:

a) BuchholzRelay.

b) Axlesandwheels.

c) Windingtemperatureindicatorsforlocalandremotemounting.

d) Oiltemperatureindicators.



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e) Bushings.

f) Bushingcurrenttransformers.

g) Coolercontrolcabinet.

h) Coolingequipment.



33/54

i) Oilpumps.

j) Fans/AirBlowers

k) Tapchangegear.

l) Terminalconnectors.

TheabovelistisnotexhaustiveandtheContractorshallalsoincludeotherboughtoutitemsinhisprogramme.

5.2 FactoryTests

5.2.1 RoutineTests

All standard routine testsinaccordancewith IS:2026withdielectric tests

corresponding to Method 2 shall be carried out on each transformer.OperationanddielectrictestingofOLTCshallalsobecarriedoutasperIS:2026.

Following additional routine tests shall also be carried out on eachtransformer:

5.2.1.1 MagneticCircuitTest

After assembly each core shall be tested for 1 minute at 2000 Voltsbetweenallbolts,sideplatesandstructuralsteelwork.

5.2.1.2 OilleakagetestontransformertankasperClause5.2.7.1below.

5.2.1.3 Magneticbalancetest

5.2.1.4 Measurementofno-loadcurrentwith415V,50HzacsupplyonLVside.

5.2.1.5 Frequencyresponseanalysis(FRA)

5.2.1.6 Highvoltagewithstandtestshallbeperformedonauxiliaryequipmentandwiringaftercompleteassembly.

5.2.2 TypeTests

FollowingtypetestsshallbeconductedononeTransformerofeachrating:

5.2.2.1 Temp.RiseTestasperIS:2026(Part-II)

Gaschromatographicanalysisonoilshallalsobeconductedbeforeandafter this testandthevaluesshall be recorded in the test report. ThesamplingshallbeinaccordancewithIEC567.FortheevaluationofthegasanalysisintemperaturerisetesttheprocedureshallbeasperIS:9434

(basedonIEC:567)andresultswillbeinterpretedasperIS:10593(basedonIEC-599).



34/54

The temperature rise test shall be conducted at a tap for the worstcombination of loading on the three windings of the transformer. TheContractorbeforecarryingoutsuchtestshallsubmitdetailedcalculationsshowingalternativespossible,onvarioustapsandforthethreetypesof

ratings of the transformer and shall recommend the combination thatresultsinhighesttemperatureriseforthetest.

5.2.2.2 TankvacuumTestasperCl.no.5.2.7.2(i)below.

5.2.2.3 TankpressureTestasperCl.no.5.2.7.2(ii)below.

5.2.2.4 Deleted.

5.2.2.5 Measurement of capacitance and tan delta to determine capacitancebetweenwindingandearth.

5.2.2.6 LightningImpulsewithstandtestinallphasesasper IS:2026(Astypetest,onlyfor220kVclass&below)

5.2.3 Additionaltypetests

Followingadditionaltypetestsotherthantypeandroutinetestsshallalsobecarriedoutononeunitofeachtype:

5.2.3.1 Measurement of zero Seq. reactance (As per IS:2026, for 3-phasetransformeronly.)

5.2.3.2 Measurementofacousticnoiselevel.

5.2.3.3 Measurementofpowertakenbyfansandoilpumps.

5.2.3.4 Measurementofharmoniclevelinnoloadcurrent.

5.2.3.5 Deleted.

5.2.3.6 Measurement of transferred surge on LV (tertiary) winding due to HVlightningimpulseandIVlightningimpulse.

5.2.4 Deleted

5.2.5 Routinetestsonbushings

Thefollowingtestsshallbeconductedonbushings

5.2.5.1Testforleakageoninternalfillings.

5.2.5.2 Measurement of creepage distance, dielectric dissipation factor andcapacitance.

5.2.5.3Drypowerfrequencytestonterminalandtapping.



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5.2.5.4 Partial discharge test followed by dielectric dissipation factor andcapacitancemeasurement.

5.2.6 TypeTestsonfittings:

Allthefollowingfittingsshallconformtotypetestsandthetypetestreportsshallbefurnishedbythecontractoralongwiththedrawingsofequipment/fittingsaspertheclauseno.9.2oftheSectionGTR.Thelistoffittingsandthetypetestrequirementis:

1. Bushing(TypeTestasperIS:2099/IEC:137)2. Buchholzrelay(TypeTestasperIS:3637andIP-55Testonterminalbox)3. OLTC(TemperatureRiseofcontact,Shortcircuitcurrenttest,Mechanical

test and Dielectric Test as per IEC:214 and IP-55 test on drivingmechanismbox)

4. CoolerControlcabinet(IP-55test)5. PressureReliefdeviceTest

ThepressureReliefDeviceofeachsizeshallbesubjectedtoincreaseinoilpressure.ItshalloperatebeforereachingthetestpressurespecifiedintransformertankpressuretestatCl.No.5.2.7.2(ii)below.Theoperatingpressureshallberecorded.Thedeviceshallsealoffafterexcesspressurehasbeenreleased.Theterminalbox/boxesofPRDshouldconformtodegreeofprotectionasperIP-55ofIS:13947.

6. MagneticOilLevelgauge&TerminalBoxforIP-55degreeofprotection.7. AirCell(Flexibleairseparator)Oilsidecoating,AirsideunderCoating,

AirsideoutercoatingandcoatedfabricasperIS:3400/BS:903/IS:7016.8. OTI&WTISwitchsetting&operation,Switchdifferential,Switchrating.9. OilpumpVacuumTestat250torrmaximum,oilpressuretestat1kg/cm2

for24hrs.,Temperaturerisetestbyresistancemethod,IP-55degreeofprotectionforterminalbox.

10.CoolingfanandmotorassemblyFreeairdelivery,Temperaturerise,soundlevel,runningatreducedvoltage,IP-55degreeofprotectionforterminalbox.

5.2.7 TankTests

5.2.7.1 RoutineTests

OilLeakageTest

All tanksandoil filledcompartmentsshall betested foroil tightnessbybeingcompletelyfilledwithairoroilofaviscositynotgreaterthanthatofinsulating oil conforming to IS:335 at the ambient temperature andapplyingapressureequaltothenormalpressureplus35KN/Sq.m(5psi)measuredatthebaseofthetank.Thepressureshallbemaintainedforaperiodofnotlessthan12hoursforoilandonehourforairduringwhichtimenoleakshalloccur.

5.2.7.2 TypeTests



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(i) VacuumTest

Onetransformertankofeachsizeshallbesubjectedtothespecifiedvacuum.Thetankdesigned forfullvacuumshallbe testedataninternal

pressureof3.33KN/Sq.mabsolute(25torr)foronehour.Thepermanentdeflectionofflatplateafterthevacuumhasbeenreleasedshallnotexceedthevaluesspecifiedbelow:

-------------------------------------------------------------------------------------HorizontalLength Permanentdeflectionofflatplate(inmm) (inmm)-------------------------------------------------------------------------------------

Uptoandincluding750 5.0

751to1250 6.5

1251to1750 8.0

1751to2000 9.5

2001to2250 11.0

2251to2500 12.5

2501to3000 16.0

Above3000 19.0

-------------------------------------------------------------------------------------

(ii) PressureTest

One transformer tank of each size, its radiator, conservator vessel andother fittings together or separately shall be subjected to a pressurecorresponding to twicethenormal headofoil or to thenormalpressureplus35KN/m2whicheverislowermeasuredatthebaseofthetankand

maintained foronehour. thepermanentdeflectionofflatplatesaftertheexcesspressurehasbeenreleasedshallnotexceedthe figurespecifiedaboveforvacuumtest.

5.2.8 Pre-ShipmentChecksatManufacturer'sWorks

5.2.8.1 Check for interchangeability of components of similar transformers formountingdimensions.

5.2.8.2 Check forproperpackingandpreservationofaccessorieslikeradiators,bushings, dehydrating breather, rollers, buchholz relay, fans, control

cubicle,connectingpipes,conservatoretc.



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5.2.8.3 Checkforproperprovisionforbracingtoarrestthemovementofcoreandwindingassemblyinsidethetank.

5.2.8.4 Gastightnesstesttoconfirmtightness.

5.2.8.5 Derivationofleakagerateandensuretheadequatereservegascapacity.

5.3 InspectionandTestingatSite

TheContractorshallcarryoutadetailedinspectionandtestingprogrammeforfieldactivitiescoveringareasrightfromthereceiptofmaterialstageupto commissioning stage. An indicativeprogramme of inspection asenvisagedbytheEmployerisgivenbelowandinthedocumentNo.OS/T&C/Bay/95 (Pre commissioning Procedures and Formats forsubstationbayequipment),whichwillbeavailableintherespectivesitesand shall be referred by the contractor. However, it is contractor's

responsibilitytodrawupandcarryoutsuchaprogrammedulyapprovedbytheEmployer.TestingofoilsampleatsiteshallbecarriedoutasperCl.3.4above.

5.3.1 ReceiptandStorageChecks

5.3.1.1 Check and record condition of each package, visible parts of thetransformeretc.foranydamage.

5.3.1.2 Checkandrecordthegaspressureinthetransformertankaswellasinthegascylinder.

5.3.1.3 Visualcheckforwedgingofcoreandcoilsbeforefillingupwithoilandalsocheckconditionsofcoreandwindingingeneral.

5.3.1.4 Check and record reading of impact recorder at receipt and verify theallowablelimitsaspermanufacturer'srecommendations.

5.3.2 InstallationChecks

5.3.2.1 Inspection and performance testing of accessories like tap changers,coolingfans,oilpumpsetc.

5.3.2.2 (i) Checkthedirectionofrotationoffansandpumps.

(ii) Checkthebearinglubrication.

5.3.2.3 Checkwholeassemblyfortightness,generalappearanceetc.

5.3.2.4 Oilleakagetest

5.3.2.5 Capacitance and tan delta measurement of bushing beforefixing/connectingto thewinding, contractorshall furnish thesevaluesfor

sitereference.



38/54

5.3.2.6 Leakagetestonbushingbeforeerection.

5.3.2.7 Measureand record thedewpoint ofnitrogen in themain tankbeforeassembly.

5.3.3 CommissioningChecks

5.3.3.1 Checkthecolourofsilicagelinsilicagelbreather.

5.3.3.2 Checktheoillevelinthebreatherhousing,conservatortanks,coolingsystem,condenserbushingetc.

5.3.3.3 Checkthebushingforconformityofconnectiontothelinesetc,

5.3.3.4 Checkforcorrectoperationofallprotectiondevicesandalarms:

(i) Buchholzrelay.

(ii) Excessivewindingtemperature.

(iii) Excessiveoiltemperature.

(iv) Lowoilflow.

(v) Lowoillevelindication.

(vi) Fanandpumpfailureprotection.

5.3.3.5 Checkfortheadequateprotectionontheelectriccircuitsupplyingtheaccessories.

5.3.3.6 Check resistance of all windings on all steps of the tap changer.Insulationresistancemeasurementforthefollowing:

(i) Controlwiring.(ii) Coolingsystemmotorandcontrol.(iii) Mainwindings.(iv) Tapchangermotorandcontrol.

5.3.3.7 Checkforcleanlinessofthetransformerandthesurroundings.

5.3.3.8 Continuouslyobservethetransformeroperationatnoloadfor24hours.

5.3.3.9 Graduallyputthetransformeronload,checkandmeasureincreaseintemperatureinrelationtotheloadandchecktheoperationwithrespecttotemperatureriseandnoiseleveletc.

5.3.3.10 Phaseoutandvectorgrouptest.

5.3.3.11 Ratiotestonalltaps.

5.3.3.12 Magnetisingcurrenttest.



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5.3.3.13 CapacitanceandTandeltameasurementofwindingandbushing.

5.3.3.14 DGAofoiljustbeforecommissioningandafter24hoursenergisationatsite.

5.3.3.15Frequencyresponseanalysis(FRA).

5.3.3.16ContractorshallprepareacomprehensivecommissioningreportincludingallcommissioningtestresultsandforwardtoEmployerforfuturerecord.

6 TechnicalParameters

i)315MVAAuto ii)105MVAautoTransformer transformer

6.1.1 Rating-H.V./I.V : i)315MVA/ ii)105MVA/105MVA315MVA

LV(Tertiary) : 105MVAreactive ii)35MVAreactive&2and5MVAactive MVAactive

6.1.2 Cooling : I)ONAN/ONAF/OFAF

6.1.3 Ratingatdifferent

cooling : 60%/80%/100%

6.1.4 TypeofTransformer: ConstantohmicImpedancetype(Refernote1)

6.1.5 Voltageratio : 400/220/33kV

6.1.6 Frequency : 50Hz

6.1.7 Phases : Three

6.1.8 Impedance(ReferNote1)

i) HV-IVimpedanceat75C :

- Max.Voltagetap : 10.3%

- Principaltap : 12.5%

- Min.Voltagetap : 15.4%

ii) HV/LVimpedance : 60%*



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iii) IV/LVimpedance : 45%*

(*impedanceareminimumindicativeonly.)

6.1.9 Service : Outdoor

6.1.10 Duty : Continuous

6.1.11 Overloadcapacity : AsperIS:6600-1972/IEC-354

6.1.12 Temperatureriseover50CAmbientTemp.

Oftopoilmeasuredby thermometer : 50C

Ofwindingmeasuredbyresistancemethod : 55C

6.1.13 Max.designAmbienttemp. : 50C

6.1.14 Windings H.V. I.V. L.V.

i) SystemFaultlevel(kA) : 40 40 25

ii) 1.2/50microsec. : 1300 950 250impulsewithstandvoltagekVp

iii) 20/200/500micro : 1050 -- --secondswitchingsurgewithstandvoltagekVp

iv) Oneminutepower : -- -- 95frequencywithstand

voltageKV(rms)

v) Windingconnection : Star Star delta

vi) Neutral : Solidlygrounded --

vii) Insulation : Graded Graded --

6.1.15 VectorGroup : ------YNaOd11------

6.1.16 TapChanger

i) Taprange : Tapchangershallbelocatedonthe220kV



41/54

sideoftheserieswindingforachieving10%ofHVvariationinthestepof1.25%.ItshallbeofconstantfluxvoltagevariationtypeasperCl.3.2ofIS:2026Part-IV-1977.

ii) Tapcontrol : Fullcapacity-onloadtapchangersuitableforgroup/independent,remote/localelectricalandlocalmanualoperationandbi-directionalpowerflow.

6.1.17 Bushing : HV IV Neut- LVral

i) Ratedvoltage(kV) : 420 245 36 52

ii) Ratedcurrent : 800 1250 800 3150

(Amp)

iii) 1.2/50microsec.lightningimpulse: 1425 1050 170 250withstandvoltage(kVp).

iv) 250/2500microsec. : 1050 -- -- --Switchingimpulsewithstandvoltage(kVp).

v) Oneminutepower : 630 460 75 95

frequencywithstandvoltagekV(rms)

vi) Minimumtotal : 10500 6125 9001300

creepagedistances(mm)

vii) Mounting : Tank Tank Tank Tankcover cover side side

6.1.18 Partialdischargelevel: 500pico-columb

6.1.19 Noiselevel : AsperNEMA-TR-1.

6.2.1 TechnicalParameters 167MVAsinglephaseautotransformer

6.2.1 Rating-H.V./I.V : 167MVA/167MVA

LV(Tertiary) : 55MVAreactive and2MVAactive

6.2.2 Cooling : ONAN/ONAF/OFAF



42/54

6.2.3 Ratingatdifferentcooling : 60%/80%/100%

6.2.4 TypeofTransformer : Constantohmic

impedancetype(Refernote1)

6.2.5 Voltageratio : 400/220/33kV




i) HV-IVimpedance

at75

C :- Max.Voltagetap : 10.3%



ii) HV/LVimpedance : 60%*

iii) IV/LVimpedance : 45%*

(*impedanceareminimumindicativeonly.)








6.2.14 Windings H.V. I.V. L.V.

i) SystemFaultlevel(kA) : 40 40 25



43/54

ii) 1.2/50microsec. : 1300 950 250impulsewithstandvoltagekVp

iii) 20/200/500micro : 1050 -- --

secondswitchingsurgewithstandvoltagekVp

iv) Oneminutepower : -- -- 95frequencywithstandvoltageKV(rms)

v) Windingconnection : Star Star delta

vi) Neutral : Solidlygrounded --

vii) Insulation : Graded Graded --


6.2.16 TapChanger

i) Taprange : Tapchangershallbelocatedonthe220kV

sideoftheserieswindingforachieving10%ofHVvariationinthestepof1.25%.Itshallbeofconstantfluxvoltagevariationtypeas

perCl.3.2ofIS:2026Part-IV-1977.


6.2.17 Bushing : HV IV Neut- LVral

i) Ratedvoltage(kV) : 420 245 36 52

ii) Ratedcurrent : 1250 2000 2000 3150(Amp)

iii) 1.2/50microsec.lightningimpulse: 1425 1050 170 250withstandvoltage(kVp).

iv) 250/2500microsec. : 1050 -- -- --Switchingimpulsewithstandvoltage(kVp).

v) Oneminutepower : 630 460 75 95



44/54


vi) Minimumtotal : 10500 6125 9001300

creepagedistances(mm)

vii) Mounting : Tank Tank Tank Tankcover cover side side

6.2.18 Partialdischargelevel: 500pico-columbs

6.2.19 Noiselevel : AsperNEMA-TR-1.

6.3 TechnicalParameters 100 MVA,220/132 kV 3 phase Auto

transformer.

6.3.1 Rating-H.V./I.V : I)100MVA/100MVA

LV(Tertiary) : No

6.3.2 Cooling : I)ONAN/OFAF

6.3.3 Ratingatdifferentcooling : 60%/100%

6.3.4 TypeofTransformer: ConstantohmicImpedancetype(Refernote1)

6.3.5 Voltageratio : 220/132kV




i) HV-IVimpedanceat75C :








45/54

6.3.11 Overloadcapacity : AsperIS:6600-1972/IEC-3546.3.12 Temperatureriseover

50CAmbientTemp.




6.3.14 Windings H.V. I.V.i) SystemFaultlevel(kA) : 40 31.5

ii) 1.2/50microsec. : 950 550impulsewithstandvoltagekVp

iii) 20/200/500micro : -- --secondswitchingsurgewithstandvoltagekVp

iv) Oneminutepower : 395 230frequencywithstand

voltageKV(rms)

v) Windingconnection : Star Star

vi) Neutral : Solidlygrounded

vii) Insulation : GradedGraded


6.3.16 TapChanger

i) Taprange : Tapchangershallbelocatedonthe132kVsideoftheserieswindingforachieving5%to10%ofHVvariationinthestepof1.25%.ItshallbeofconstantfluxvoltagevariationtypeasperCl.3.2ofIS:2026Part-IV-1977.


6.3.17 Bushing : HV IV Neut-



46/54

ral

i) Ratedvoltage(kV) : 245 145 36

ii) Ratedcurrent : 800 800 800

(Amp)

iii) 1.2/50microsec.lightningimpulse: 1050 650 170withstandvoltage(kVp).

iv) 250/2500microsec. : -- -- --Switchingimpulsewithstandvoltage(kVp).

v) Oneminutepower : 460 275 75


vi) Minimumtotal : 6125 3625 900creepagedistances(mm)

vii) Mounting : Tank Tank Tankcover cover side

6.4 TechnicalParameters 50MVA,132/66kV3phaseAutotransformer.

6.4.1 Rating-H.V./I.V : I)50MVA/50MVA

LV(Tertiary) : No

6.4.2 Cooling : I)ONAN/OFAF

6.4.3 Ratingatdifferentcooling : 60%/100%

6.4.4 TypeofTransformer: ConstantohmicImpedancetype

6.4.5 Voltageratio : 132/66kV




i) HV-IVimpedance

at75C :



47/54








Oftopoilmeasuredby

thermometer : 50

C



6.4.14 Windings H.V. I.V.i) SystemFaultlevel(kA) : 31.5 31.5

ii) 1.2/50microsec. : 550 325

impulsewithstandvoltagekVp

iii) 20/200/500micro : -- --secondswitchingsurgewithstandvoltagekVp

iv) Oneminutepower : 230 140frequencywithstandvoltageKV(rms)

v) Windingconnection : Star Star

vi) Neutral : Solidlygrounded

vii) Insulation : GradedGraded

6.4.15 VectorGroup : ------YnaO------

6.4.16 TapChanger

i) Taprange : Tapchangershallbelocatedonthe66kVsideoftheserieswindingforachieving+/to10%of



48/54


49/54

7.3 Current transformer secondary leads shall be brought out to aweatherproof terminalboxneareachbushing. These terminalsshallbewiredouttocoolercontrolcabinet/marshallingboxusingseparatecablesforeachcore.

7.4 BushingCurrenttransformerparametersindicatedinthisspecificationaretentative and liable to changewithin reasonable limits. TheContractorshallobtainEmployer'sapprovalbeforeproceedingwiththedesignofbushingcurrenttransformers.

7.5 TechnicalParameters

7.5.1 Current TransformerParametersfor1-ph, 105MVAand3-ph315MVA400/220/33kVAutoTransformers

Oneachphaseconnection

HV IV NeutralSide side side

(a) Ratio

Core-1 1000/1A 1000/1A 1000/1A

Core-2 600/1A 1000/1A -

(b) Minimumkneepointvoltageandaccuracyclass:

Core-1 1000V 1000V 1000VClassPS ClassPS ClassPS

Core-2 0.2class 0.2class -

30VAISF530VAISF5

(c) MaximumCTResistance

Core-1 2.5ohms 2.5ohms 2.5ohms

Core-2 - - -

(d) Application

Core-1 Restricted Rest- Restricted(Nearthewdg) earth ricted earth

fault earth faultfault

Core-2 Metering Metering -

(e) Maximummagnetisation Core-160mA 60mA60mA



50/54

current(atknee Core2- - -pointvoltage)

7.5.2 CurrentTransformerParametersfor1-ph,167MVA,400/220/33kVAutoTransformers



(a) Ratio

Core-1 1600/1A 1600/1A 1600/1A

Core-2 1000/1A 1600/1A -


Core1 1600V 1600V1600V

ClassPS ClassPS ClassPS

Core-2 0.2class 0.2class

30VAISF5 30VAISF5----


Core-1 4.0ohms 4.0ohms 4.0ohmsCore-2 - - -

(d) Application


fault earth faultfault


(e) Maximummagn Core-1 25mA 25mA25mAetisationcurrent Core2 - - -(atkneepointvoltage)

7.5.3 Current Transformer Parameters for3-ph,100MVA,220/132kV AutoTransformers



51/54



(a) Ratio

Core-1 600/1A 600/1A 600/1A

Core-2 300/1A 500/1A -



Core-2 0.2class 0.2class -

30VAISF530VAISF5(c) MaximumCTResistance


Core-2 - - -

(d) Application


fault earth faultCore-2 Metering Metering -

(e) MaximummagnetisationCore-1100mA 100mA 100mA


7.5.4 Current Transformer Parameters for 3-ph, 50MVA, 132/66kV Auto

TransformersOneachphaseconnection


(a) Ratio

Core-1 300/1A 300/1A 300/1A

Core-2 300/1A 300/1A -

(b) Minimumkneepointvoltageandaccuracy



52/54

class:


Core-2 0.5class 0.5class -15VAISF515VAISF5



Core-2 - - -

(d) Application

Core-1 Restricted Rest- Restricted

(Nearthewdg) earth ricted earthfault earth fault


(e) MaximummagnetisationCore-1100mA 100mA 100mA


7.6 NOTE:

7.6.1 AccuracyclassPSasperIS:2705

7.6.2 Class(fortherelevantprotectionandduties)asperIEC185.

7.6.3 Parameters of WTI CT for each winding shall be provided by the

contractor.

8.0 OilStorageTank

8.1 General

Thisspecificationcoverssupplyofoilstoragetankof15cubicmetercapacityalongwithcompleteaccessories.

8.2 Standard

TheoilstoragetankshallbedesignedandfabricatedasperrelevantIndianStandardse.g.IS:803orotherinternationallyacceptablestandards.

8.3 Specifications

Transformeroilstoragetanksshallbetowable&restedonpneumatictyres

ofadequatequantity&size.Thetankshallbetocylindricalshape&



53/54

mountedhorizontallyandmadeofmildsteelplateofadequatethickness.Sizeofthestoragetankshallbeasfollows:

Diameter : 2.5meter

Capacity : 15cubicmetre

Thetankshallbedesignedforstorageofoilatatemperatureof100C.

8.3.1 The Bidder may further note that maximum height of any part of thecompleteassemblyofthestoragetankshallnotexceed4.0metresaboveroadtop.

8.3.2 Thetankshallhaveadequatenumberofjackingpadsothatitcanbekepton jackwhile completely filledwith oil. Thetankshall beprovidedwithsuitablesaddlessothattankcanberestedongroundafterremovingthe

pneumatictyres.

8.3.3 The tankshall alsofittedwithmanhole,outside& insideaccessladder,silicagelbreatherassembly,inlet&outletvalve,oilsamplingvalvewithsuitableadopter,oildrainagevalve,airventetc.Pullinghookonbothendsofthetankshallbeprovidedsothatthetankcanbepulledfromeitherendwhilecompletelyfilledwithoil.Biddershallindicatetheenginecapacityinhorsepowertopullonetankcompletelyfittedwithoil.Oillevelindicatorshallbeprovidedwithcalibrationintermsoflitresothatatanytimeoperatorcanhaveanideaofoil inthe tank. Suitablearrangement shallalsobeprovidedtopreventoverflowinthetank.Fournos.suitablerubber

hoseswithcouplersandunionseachnotlessthan10metrelongshallalsobeprovided.

8.3.4 Theinternal&externalsurfacestobepaintedshallbeshotorsandblastedtoremoveallrustandscaleofforeignadheringmatterorgrease.Allsteelsurfacesincontactwithinsulatingoilshallhavepaintedwith twocoatsofheat&oilresistantanti-corrosivepaint.Allsteelsurfacesexposedtoweathershallbegivenaprimarycoatofzincchromate,secondcoatofoil&weatherresistantpainto

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