132-33kv-substation.docx

CHAPTER!INTRODUCTION

CHAPTER2CLASSIFICATIONOFSUBSTATIONS

CHAPTER-3 SINGLELINEDIAGRAM(SLD)

CHAPTER-4BRIEF DISCRIPTION OF INSTRUMENT IN THESUBSTATION

CHAPTER-5 PROTECTION FORVARIOUSEQUIPMENTS

A

MiniProjectReporton OPERATIONANDMAINTENANCEOF132/33KVSUBSTAT ION MiniProjectSubmittedinFulfillmentofTheRequirementsForTh eAwardofTheDegree BACHELOROFTECHNOLOGY IN

ELECTRICALANDELECTRONICSENGINEERING SubmittedBy

G.RAVIKUMAR R.TRIVENII.VENKAT ESWARLU G.RAJASHEKAR REDDY

116U1A0213 116U1A0242 116U1A0217 116U1A0216

UndertheguidanceofMs. R.RAMADEVI B.Tech Asst.Professor,EEEDepartment

DEPARTMENTOFELECTRICALAND ELECTRON ICSENGINEERING

SreeKavithaEducationalSociety's SREEKAVITHAINSTITUTEOFSCIENCE&TECHNOLOGY

(ApprovedbyAICTE-NewDelhi&AffiliatedtoJNTUHyderabad)KRISHNAPURA M(V),MADHIRA(M),KHAMMAM507203(T.S)

SreeKavithaEducationalSociety's SREEKAVITHAINSTITUTEOFSCIENCE&TECHNOLOGY (ApprovedbyAICTE-NewDelhi&AffiliatedtoJNTUHyderabad)KRISHNAPURAM(I/),MADHIRA(M),KHAMMAM507203(T.S)

CERT/FICATE

Thisiscettifythattheminiprojectreport Entitled

OPERATIONANDMAINTENANCEOF132/33KVSUBS TATION Isabonafide

recordof workcati-iedoutby

Weherebyaccordmyapprovalofitasaminiprojectreportcarriedoutandpresentedinamannerrequiredfo ritsacceptanceinfulfillmentforawai·dofdegreeofBachelorofTechnologyinElectrical&ElectronicsEn

gineeringinJawahai·JalN ehtuTechnologicalU ni versity,Hyderabad.

PROJECTGUIDEMs.R.RA MADEVT,B.Tech AssistantProfessor

HEADOFTHEDEPARTMENTM r.G.V ENKAT,M.Tech Assistantprofessor.

DECLARATION Wedeclarethattheprojectreportentitledisdonebyus,submitted inpattialfulfillmentoftherequirementsfortheawai·dofthedegreeinBACHELOROFTECHNOL

OGY.

G.RAVI KUMAR R.TRIVENI I.VENKATESWARL U G.RAJASHEKARREDDY

I

PLACE :KRISHNAPURAM

116U1A0213 116U1A0242 116U1A0217 116U1A0216

ABSTRACT A substation receives electrical power from generating station via incoming transmission line and delivers electrical power through feeders and this is used for controlling the power on different routes. Substations are integral part of a power system and form important part of transmission and distribution network of electrical power system. Their main functions are to receive energy transmitted at high voltage from the generating stations, reduce the voltage to a value appropriate for local distribution and provide facilities for switching some sub-station are simply switching stations different connections between various transmission lines are made, others are converting sub-stations which either convert AC into DC or vice-versa or convert frequency from higher to lower or vice-versa. The various circuits are joined together through these components to a bus-bar at substation. Basically, sub-station consists of power transformers, circuit breakers, relays, isolators, earthing switches, current transformers, voltage transformers, synchronous condensers/capacitor banks etc. This mini project covers the important equipments & their function in a sub-station. And also an attempt is made to cover the general maintenance of substation and checks the observations to be made by shift engineer. As a part of case study we are going to visit a 132/33Kv TRANSCO substation at Ibrahimpatnam, Rangareddy.

INDEX

CHAPTER

TITLE

PAGENO

LIST OF FIGURES LIST OF ABBREVATIONS CHAPTER-1

INTRODUCTION 1.1 l.2

IntroductionofSubstation Constructin oASubstation l.2.1 SelectionofSite

1 1

2.1 2.2

CLASSIFICATIONOFSUBSTATION Accordi ngToTheRequirements Accordi ngToTheConstructionalFeatures

3 3

3.1 3.2

SINGLELINEDIAGRAM Singlelinediagram FeederCircuit

4 4

CHAPTER-2

CHAPTER-3

CHAPTER-4

BRIEFDISCRIPTIONOFINSTRUME NTSINTHESUBSTATION 4.1 4.2

4.3 4.4 4.5

LightningAtTester 4. 1. 1 TheActionofTheLightning Earthing 4.2.1 InAllSubstationsThereShallBe ForEarthingTh eFollowing CapacitorV oltageTransformers(CVT) 4.3.1

Specificationsof

5 5 7 Provision 7 7

CVT

9

Wavetrap InstrumentTransfonner

4.5.1

CurrentTransformer

9 10 (C.T)

10

4.5.1.1 BasicDesignPri ncipleof C.T 4.5.1.2 SimpleLineDiagramof C.T 4.5.1.3TestsGenerall yToBeConductedonC.T 4 .5. 1 .4 Specificationsof 4.5. 1.5 Specificationsof

4.5.2

11 12 12

HVCT LVCT

12 13

PotentialTransformers

4.5.2.1

14 BasicDesignPri ncipl e ofVoltageTran sformers

4.5.2.2

SimpleLineDiagramof VoltageTransformers

4.5.2.3 P.T

15

TestsGenerall yToBeCondu onThe P.T's 15

cted

4.5.2.4

15

GeneralChecks 16

For

4.6

4.9 4.7 4.8

CHAPTER-5 5.1 5.2 5.3

CircuitBreaker(C.B) 4.6. l SF6 Circui tBreaker

16 18

4.6.2 4.6.3 4.6.4

VaccumCircuitBreaker

18

NamePlateDetailsof132KVSF6C.B

18

NamePlateDetailsof33KVVaccumC.B

19 19 20

Bus Transformer

4.8.1 4.8.2 4.8.3

BasicPrinci ple

20

blduction

21

Law

Specificationsof132KV/33KV Capaci tor Bank Attach edToTh eBus 4.9.1 CapacitorControlisUsuallyDoneToAchive TheFollowingGoals

PROTECTIONFORVARIOUSEQUIPMENTS Transformer Protection FeederProtection ImportantPointsToBeKeptInVi ewWhil eLayi ng OutTheSubstation

AutoT/F

23 23 24

25 25 26

CONCLUSION

27

REFERENCES

28

LISTOFFIGURES Fig:1.2.l

DiagramofSubstation

Fig.4.1.1.1

(i)SurgeDive1ter

Fig:4.1.1.2

(ii)CharacteristicsofTheNonLinearResisterLightningA trester

Fig:4.3.1

CircuitDiagramofCVT.

Fig:4.3.2

CapacitorVoltageTransformer.

Fig:4.4.lFi

WaveTrap

g:4.5. l.l.l

CutTentTransfotmer

Fig:4.5.1.2.l LineDiagramofC.TFig :4.5.2.1.1 PotentialTransfotmer. Fig:4.5.2.2.l

LineDiagramofV.T

Fig:4.6.1

Circuit

Fig:4.8.1

BreakerElectri cal Transfotmer.

Fig:4.8.1.1

IdealTransfotmer.

Fig:4.8.2.1

MutualInduction.

Fig:4.8.2.2

ThreePhase50MVAAutoTransformer.Capacit

Fig:4.9.1

orBankInTheDistributionSystem.

Fig:4.9.1.1

ReactiveLosses.

LISTOFABBREVIATIONS EHV

-

ExtraHighV oltageSLD

-

SingleLineDiagramPT PotentialTransfotmerCT

-

Cu1TentTransfotmerHVCT -HighV oltageCT LVCT

-LowV oltageCT

CVT

-

CapacitorVoltageTransformerLA

-

Lighteni ngAtTestors ES

-EarthSwitches

CB

-

CircujtBreakerHYsideHi ghVoltageSideLVside -LowV oltageSide PLCC

-

PowerLineCarrierCommunicationOLTC OnloadTapChanger HGFuse OTT

-HornGapFuse -OilTemperatureIndicator

-

WTI

-WindingTemperatureIndicator

IDMTCharactetistics-InverseDefiniteMinimumTimeCharactetistics.

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

1.1 INTRODUCTIONOFSUBSTATION The present day electrical power system is A.C. i.e. electric power is generated, transmitted and distributed in the form of alternating current. It is delivered to the consumers through a large network of transmission and distribution. At many places in the line of th e power system, it may be desirable and necessary to change some characteristic (e.g. voltage, A.C. to D.C., frequenc y, Power factor etc.) of electric supply. This is accomplished by suitable apparatus called sub-station. For example, generation voltage (11 kv or 6.6 kv) at the power station is stepped up to high voltage (say 132 kv or 220 kv) for transmission of electric power. The assembly of apparatus (e.g. transformer etc.) used for this purpose is the sub-station. Similarly, near the consumer’s localities, the voltage may h a v e to be stepped down to utilization level. This job is again accomplished by a suitable apparatus called substation.

1.1

CONSTRUCTIONOFASUBSTATION At thetimeofconstructingasubstation ,wehavetoconsidersomefactorswhichaffectthesub

stationefficiencylikeselectionofsite.

1.2.1SelectionofSite Mainpoi ntstobeconsideredwhil eselectingthesiteforEHVSub-Stationareasfollows: )>

Thesitechosen

should beas nearto aspossible.

theload

centre

)>

Itshouldbeeasilyapproachablebyroadorrailfortranspo1tationofequi p ments. )>

Landshouldbefairlylevelledtomini mizedevelop1nentcost.

DEPT OFEE E,SKIT.

Page1

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION )>

ThesubstationsiteshouldbeasneartothetownIcitybutshouldbeclearofpublicplaces,aerodro mes,andMilitaryIpoliceinstallations.

DEPT OFEE E,SKIT.

Page2

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

)>

Thelandshouldbehavesufficientgroundareatoaccommodatesubstatio nequjpments ,buildings,staffquarters,spaceforstorageofmaterial ,suchasstoreyards andstoreshedsetc.wi throadsandspaceforfutureexpansion. )>

Set back State

distances

ii-om

various

roads

such

as National

High ways,

)>

WhileselectingthelandforthesubstationpreferencetobegiventotheGovt .land overPrivateland .

Fig:1.2.1.1DiagramofSubstation

DEPT OFEE E,SKIT.

Page3

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

Thereareseveralwaysofclassifyi ngsubstations.However,thetwomostimportantwaysofclassifyingthemareaccordi ngto(1)servicerequireme ntand(2)constructionalfeatures.

2.1 ACCORDINGTOTHEREQUIREMENT AsubstationmaybecalledupontochangevoltagelevelorimprovepowerfactororconvertA.C.powerintoD.C. poweretc.Accordingtotheservicerequjrement,sub-stations1naybe classifiedinto: 1Transformersub-stations

2 Switchingsub-stations 3 Power factorcorrection sub-stations 4 Frequencychangersub-stations 5 Convertingsub-stations 6 Industrialsub-stations

2.2 ACCORDINGTOTHECONSTRUCTIONALFEATURES A

sub-

stationhasmanycomponents(e.g.circuitbreakers,switches,fuses,insttu mentsetc.)whichmustbehouse dproperlytoensurecontinuousandreliableservice.Accordingtoconstructionalfeatures,thesubstationsareclassifiedas I Indoor sub-station 2 Outdoorsub-station 3 Undergroundsubstation4Pole-mountedsubstation

DEPT OFEE E,SKIT.

Page4

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

3.1SINGLELINEDIGRAM ASingleLineDiagram(SLD)ofanElectticalSystemistheLineDiagramoftheconcernedElect ricalSystemwhichincludesalltherequiredelectticalequi pmentconnectionsequencewisefromthepo i ntofentranceofPoweruptotheendofthescopeofthemention edWork .Asinthecaseofl32KVSubstati on,theSLDshallshow

Lighteni ng

Arrestor,C.T/P.TUni t ,Isolators,ProtectionandMetetingP.T&C.T.CircuitBreakers,againIsolatorsa ndcircuitBreakers,MainPowerTransfotmer,allprotectivedevices/relaysandotherspecialequ ipmen tlikeCVT,GU ARDRIN GS,etcasperdesigncriteria.Andthesymbolsareshownbelow.Thereareseve ralfeedersenterintothesubstationandcarryingoutthepower.As thesefeedersenterthestationtheyaretopassthroughvaiiousinstruments .

3.2.FEEDERCERCUIT 1LighteningAtTestors2 CVT 3 Wavetrap 4 Isolatorswi thEarthSwitch

5 CtuTentTransfotmer 6 CircuitBreaker 7 FeederBusIsolator 8 BUS 9 PotentialTransformerinth eBuswithaBusIsolator.

DEPT OFEE E,SKIT.

Page5

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

4.1LIGHTENINGARRESTERS Lighteni ngarrestersaretheinstrumentsthatareusedintheincomingfeederssothatto preventthehighvoltageenteringthemai nstation.Thishighvoltageisverydangeroustotheinstt11mentsus edinthesubstation.Eventheinstrumentsareverycostl y,sotopreventanydamagelighteningarrestersareu lighteni ngarrestersdonotletthelighteningtofallonthestation.Ifsomelighteni ngocctu-

sed.The

sthearrestorspullthelighteni ngandgroundittotheearth.Inanysubstationthemainimpottantisofprotecti onwhichisfirstlydonebytheselighteni ngatTestors.ThelighteningatTestersai·egroundedtotheeatthsot hatitcanpullthelighteni ngtoth eground. Theseai·elocatedattheentranceofthetransmi ssionlineintothesubstationandasneat·aspossibleto thetransfotm erterminals. Thelightni ngatTesters orsurgedivertersprovideprotectionagainstsuchsurges.Alightni ngatTesterorasurgediverterisaprotect ivedevice,whichcond uctsthehighvoltagesu rgesonthepowersyste1ntotheground.

•

f

: 'C ") :

T

t

I

I

:T: .-'.i_.J

[email protected]. aa"'J."C

...

I

'I

.

--;;--.

•••:t••1111e'"z.11• :re$i" .'1Slll01

-

.

C"c.a·


Fig.4.1.1.1(i)SurgeDiverter (ii)CharacteristicsofTheNonLinearResister

DEPT OFEE E,SKIT.

Pages

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

Fig:4.1.1.2LightningArrester 4.1.2The ActionofTheLightningArresterorSurgeDiverterisasUnder Undernormal

);:>-

operation,thelightnin garresterisoffthelinei.e.itconductsnocturenttoearthorthegapisnon conducting. );:>-

Ontheoccu tTenceofovervol tage,theairinsulationacrossthegapbreaksdownandanarcisfonn edproviding

a

low

resistance

path

forthe

surge

to

theground.Inthisway,theexcesschargeonthelineduetothesurgeishatmlesslyconductedth rou ghthe atTestertothegroundinsteadofbei ngsentbackovertheline. ItiswotthwhiletomentionthefunctionofnonlinearresistorintheoperationofatTester.Asthegapspai·ksoverduetoovervoltage,theai·cwouldbeas hottcircuitonthepowersystemandmaycausepowerfollowctuTentintheatTester.Sincethecharacteristicoftheresistoristoofferlowresistancetohighvol tage(orcu1Tent), itgivestheeffectofshortcircuit.Afterthesurgeisover,theresistoroffershighresistancetomakethega pnonconducting The LA vol tage rating cotTesponding to the system voltages ai·e indicatedbelow Rated

syste1n

Highestsyste1n

AlTesterratin ginKV

Voltage(KV)

Voltage(KV)

11

12

9

33

36

30

66

72.5

60

132

145

120/132(latex)

220

245

198/216(latex)

400

420

336

Effectivelyearthedsyste1ns

Tahle:4.1.2.1LAVoltageRating 4.2EARTHING DEPT OFEE E,SKIT.

Page6

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

Theearthingpracticeadoptedatgeneratingstations,substationsandlinesshouldbeinsuchamannerastoprovideinunitsofohms );>-

Safetytopersonnel

);>-

MinimumdamagetoequipmentasaresultofflowofheavyfaultcurrentsImpro vereliabilityofpowersupply );>-

Largesub-stations-l

);>-

Small sub-stations-2

);>-

Power stations -0.5

);>-

Distribution transformerstations-5

4.2.1InAllSub-Stations ThereShallbeProvisionForEarthingTheFollowing );>-

The neutral

poi nt of earth

separate system should have an

independenteatth,whichinttu·nshouldbeinterconnectedwiththestationgroundin g mat Equipment 11-amework andothernon-current Allextraneousmetallic );>-

catTyingpatts.

fi-ameworknotassociated

withequipment

(twoconnections)

The eaith conductorof the mat could be buried under eaith to economicaldepthofbtuialofthemat 0.5meters.

4.3CAPACITORVOLTAGETRANSFORMER( CVT) Acapacitor voltagetransfotmer(CVT)is atransfotmer used in power systems tostep-down extrahighvoltage signals and provide low voltagesignalseitherfortneasurementortooperateaprotectiverelay TheseaiehighpassFilters(carrierfrequ en cy50KHZto500KHZ)passcatTierfrequen cytocatTierpanelsandpowerfrequ encyparameterstoswitchyai·d.blitsmostbasicformthedeviceconsistsoft hreepai·ts :twocapacitorsacrosswhichth evoltagesignalissplit, ani nd u ctiveele1nentu sedtotunethedeviceandatransformeru sedtoisolateandftutherstep-downthevoltage .

DEPT OFEE E,SKIT.

Pages

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

Hlgnvolt•g• tMm1nal

c,

Tr.ttnSfotmer

II

c2 (3tot.Ind

1·rm1nI

Fig:4.3.1CircuitDiagramofC.V.T Thedevicehasatleastfourtetminals,ahigh-voltagetetminalforconnectionto thehighvoltagesignal,agroundtetminal

and

atleastonesetofsecondaryterminalsforconnectiontotheinstrumentationorprotectiverelay. CVTsaretypicallysinglephasedevicesusedformeasutingvoltagesinexcessofonehundredKVwheretheuseofvoltage transfotmerswouldbeuneconomical.Inpracticethefirstcapacitor,Cl,isoftenreplacedbyasta ckofcapacitorsconnectedinseties.Thisresultsinalargevoltagedrop

across

the

stack

ofcapacitors,thatreplacedth efirstcapacitorandacomparativelys1nallvoltagedropacrossthes econdcapacitor,C2,andhencethesecondarytenninals.

Fig:4.3.2CapacitorVoltageTranform er.

DEPT OFEE E,SKIT.

Pages

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

4.3.1SpecificationsofCVT CVTtypeWeig

:CVEB/245/1050

ht

:665kg

TotaloutputsimultaneousOutput

:250V A

maxi mum

:750V Aat50°C

Ratedvoltage

:A-N,220N3

Highestsystemvoltage

:A-N,245/-J3

Ratedfrequ ency

:50Hz :Al-N,20N3KV

Nominalintetmediatevol tageV olta

:1.2Cont.1.5/30sec

gefactor

:4400pF+10%-5oo /

'HF'capacitance

:4840pF+10%-5%

Pri marycapaci tanceClSeconda rycapaci lanceC2V oltageratio

:48400pF+10%-5%

V oltage

:220000/../3/110/../3/110-110/../3 :110/../3

BurdenClass

:150

110-110/../3 100

:0.5

4.4WAVETRAP Wavetrapisaninstrumentusingfortrapping

of

the

wave .The

function

ofthiswavetrapisthatittrapstheunwanted waves .Itsshapeislikeadt11m.Itisconnectedtothemai ninco1ningfeedersothatitcantrapthewaveswhic hmaybedangeroustotheinstn1mentsinthesubstation.Generallyitisusedtoexcludeunwantedfrequ en cycomponents,suchasnoiseorotherintetference,ofawave.

Note: Trapsareusuallyu nabl etopetmitselectionofunwantedor intetferingsignals.

DEPTOFEEE,SKIT.

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OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

LinetrapalsoisknownasWavetrap.Whatitdoesistrappingthehighfrequencyco1nmunication signal ssentonthelinefro1ntheremotesubstationanddivertingthemtothetelecom/teleprotectionpaneli nthesubstationcontrolroomthroughcouplingcapacitor.

Fig:4.4.1Wave Trap ThisisrelevantinPowerLineCar1ierCommunication(PLCC)systemsforcommunicationa1nong vaiioussubstationswi thoutdependenceonthetelecomcompanynetwork.The signalsai-e primai·ily tele protection signal sand in addition,voice and data communicationsignals.TheLinetrapoffershighi1npedancetothehighfrequ encycommunicationsigna lsthusobstructstheflowofthesesignalsintothesubstationbusbai'S.Iftheseai·enotp1esentinthesubstation,thensignallossismo1eandcommunicationwillbeineffective/probablyimpossible .

4.5 INSTRUMENTTRANSFORMERS "InstrumentTransfo1mersa1edefinedastheinsll11mentsinwhichthesecondai·ycu1Tentorvoltageissubstantiallyproportionaltothepr imai·yctu-1-entorvol tageanddiffersinphasefro1n itbyananglewhichisapproxi matelyzeroforanappropriatedirectionofconnection''. DirectmeasurementofctuTentorvoltage in high voltage system is notpossiblebecauseofhighvaluesandinsulationproblemsofmeasuringinstrumentstheycannotbedirec tlyusedforprotectionpu1poses. Instrumenttransfo1mersai-eoftwotypes: )>-Cur1-entTransformers )>- VoltageTransfonne1'S

4.5.1CurrentTransformers: Cur1-enttransfo1merisacu1Tentmeasu1ingdeviceusedto1neasurethectuTents inhighvol tagelines

di1-ectly

by

stepping

down

thecurrents

tomeasurableval uesby

meansofelectromagneticcircui t . DEPTOFEEE,SKIT.

Page10

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

4.5.1.1BasicDesignPrincipleofCurrent Transformers Thebasicprincipleinducedindesigningofcurrenttransfor mersisPtimaryamperetu n1s=Secondaryamperettuns IpxN p=IsxNs Where,Ip-Primarycurrent Np-PrimaryWi ndi ngTurns Is-SecondaryCuti-ent;Ns-SecondaryWi ndi ngTtu·n

)>

Amperettunsplaysv eryimpottantroleindesigni ngctuTent transfotmers.

)>

Current transfo nnersmustbe connectedin seriesonly.

)>

Currenttransfotmerh aslessnoofturns inpri maryandmorenoofturnsinsecondary.

)>

Thesecond aryctuTentisdirectlyproportionaltoptimarycurrent.

)>

ThestandardsapplicabletoCT'sareIEC-60044-1andIS-2705.

Fig:4.5.1.1.1CurrentTransformer

DEPTOFEEE,SKIT.

Page11

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

4.5.1.2 SimpleLineDiagramofCurrentTransformer Thelinediagramofacurrenttransfotmercontainsdifferentco1nponents: Pl

Fig:4.5.1.2.1LineDiagramofC.T 4.5.1.3 TestsgenerallytoheconductedonCT );>-

Insulation

resistance

values

(IR

values):

secondai·ycorel,pri mai·ytosecondai·ycore2,corelto

Primary

to

eatth,

eatth,

.

·y prtmai

core2to

to

eatth

andcoreltocore2.Ptimarytoeatthandpri1nai·ytosecondai·ycoresat-etobechecked wi thSKYmotoroperatedinsulationtester(megger)andsecondarytoeatthvaluesaretobec heckedwi thlOOOVinsulationtesterorpreferablywithSOOYinsulationtester.

4.5.1.4

);>-

Ratiotest:Primai·yinjectiontestistobeconductedforthisputpose

);>-

TAN-DELTAtest:on 132KV CTsand above

);>-

Secondai·yand lead 1-esistance check

);>-

Secondai·y injection check

);>-

Primai·y injection check

SpecificationsofHVCT

TypeFrequency

:IT-24S

H.S.V

:SOHz

BIL weight Totalweight

:24SKV :460/lOSOKVOil :360kgs :12SOkgs

DEPTOFEEE,SKIT.

Page12

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

RATIO

800-600-400/1-1-1-1-1 2 3 4

CORENUMBER RATEDPRIMARY CURRENT(A) RATEDSE CONDARYC URRENT(A)

l

l

l

OUTPUT(VA)

--------

----------

ACCURACYCLASS I.S.F/A.L.F

PS ----

PS ---

5

800

TURNRATIO

1

2/1600

RCTat75CAT800/1 (ohms)

6

Table:4.5.1.4.1

-----------PS ---

1

1

--------

30

PS ---

1200

800

6

6

0.5 <=5

---

SpecificationsofHVCT.

AttherateofLY(l32KV)sidewecanuse1:3coreCT.ThespecificationsofLVCTaregivenb elow:

4.5.1.5 SpecificationsofLVCT TypeFrequency

:IT-145

HSV/NSV BIL

:50Hz

weight Totalweight

:145/132KV :650/275KVOil :75Kg :550Kg

DEPTOFEEE,SKIT.

Page13

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

500/1-1 0.66-1 '

RATIO CORENUMBER

l

2

3

RATEDPRIMARY 500

CURRENT(A) 500/1

500/1

50010.66

500/1

lsl-ls2

2sl-2s2

2sl-2s3

3sl-3s2

1

1

0.66

1

OUTPUT(VA)

20

-------

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

20

ACCURACYCLASS

Sp

I.S.F/A.L.F

20

--------

---------

<=5

--------

<=5

---------

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

PRIMARY& SECONDARYC ONNECTION RATEDSECONDARY CURRENT(A)

Rctat75°C (Ohms)

0.2

PS

Table:4.5.1.5.1 SpecificationsofLVCT

NOTE );>-

CT secondary circuit and PT pri mary should never be open circuited. It isvul nerabletotheCT!PT

);>-

CTprimarycircuitandPTsecondaryshouldneverbeshortcircuited.

4.5.2PotentialTransformers(PT) Aninsttumenttransformerinwhichthesecondaryvoltage,innormalconditionsofuse,issubsta ntiallyproportionaltotheptimaryvol tageanddiffersinphasefromitbyananglewhich is approxi mately zero for anapproptiatedirectionofthe connections.

DEPTOFEEE,SKIT.

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OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

4.5.2.1 BasicDesignPrincipleofVoltageTraru.former's

ThebasicptincipleinvolvedinthedesigningofVoltageTransformerisVo ltageRatio=TtunsRatio Vp/Vs=N p/Ns Thus NsxVp=NpxVs Asheavypri maryvoltageswillbereducedtolowsecondaryvoltages ,itwillhavemoreturnsinthe primary&lesstun1sinthesecondary.Itmustalwaysbeconnectedinparallelonly .Evenifweconnect itdirectlyfromhighvoltagetoearth,itisnotgoingtobeashortcircujtasitspri marywi ndi nghasveryhighres istance.Itscoreisasetofassembledla1ninations.Itoperatesatconstantfluxdensity.ThestandardsareIEC600044-2andIS-3156.

Fig:4.5.2.1.1Potential Transformer. 4.5.2.2 SimpleLineDiagramofVoltageTransformer HVTERMINAL PR!

NEUTRAL /TERMINAL

• b

SECONDARY TERMINALS

Fig:4.5.2.2.1LineDiagramofVT. 4.5.2.3 TestsgenerallytoheconductedonthePTs );>-Insulationresistancev alues(IRvalues):

primaryto earth, primarytosecondarycore-

1,primarytosecondary core-2, corel to earth, core 2to eatthandcore-Itocore2.Thesevaluesat-etobechecked

with

lOOOYinsulationtester(megger)orpreferablywithSOOYinsulationtester. DEPTOFEEE,SKIT.

Page15

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

);:>-

RatioTest:Byapplyi ngsinglephasevoltageacrossprimarythevoltageinducedinthese condarywindi ngistobe1neasure.Thisisapproxi matelyequaltovoltageappliedinthep timarywin dingorvoltageratioofthePT. );:>-

Polarity test: at the

time ofcommissioning

(at least on the PTsconnected

to

revenuemeters) );:>-

PTsecondaryinjection check

4.5.2.4Generalch ecksforPT );:>-

MechanicalalignmentforPTpowerjaws

);:>);:>-

PTprimarywindi ngstareatthing Tightnessof allconnections

);:>-

Ptimary/secondai·y fuse ratings

);:>-

PT specifications fuPTsnoofsecondai·ycoresislormorethan1 basedontherequiretnent.Ge

nerallyin1lKVor33KVbusPTs,thereisonesecondai·ywindi ngwh ichisusedbothf orprotectionandtneteringandinl32KVandabove,thereatetwosecondai·ycores.Firstcoreisofmetetingcorewithl.0or0.5or0.2accuracyclas ses.Thiswillbeusedmetering,dit-ectionalovercur1entprotectionanddistanceprotection.

4.6 CIRCUITBREAKER Thecircuitbreakersateusedtobreakthecircuitifanyfaultoccursinanyoftheinstntment.Thesecircuitbteakerbt-eaksforafaultwhichcandamageotherinstrumentinthestation.For anyunwantedfaultoverthestationweneedtobteakthelinecutTent.Thisisonlydoneautomaticallybythecircuitbt-eaker. );:>);:>-

Operationmechanismfunction , Arcquenchi ngfunction.

DEPTOFEEE,SKIT.

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OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

Fig:4.6.1CircuitBreaker

:;;.. variousoperatingmechanisms l

Sptingchargemechanism,

2 3

Pneumaticmechanism, HydraulicMechanism.

:;;.. Arcquenchingmedium 1

Bulkoil(calledbulkoilcircuitbreakers-BOCB)

2

Minimumoil(calledmini mumoilcircui tbreakers-MOCB)

3

Naturalair(calledaircircuitbreakers-ACB)(415v)

4

Forcedair(calledairblastcircuitbreaker-ABCB)

5

Vacuum(calledvacuumcircuitbreaker-VCB)

6

SF6gas(calledSulphtu·Hexatluoride-SF6gasCB)

Thepresenttrendisupto33KV,VCBsareprefetTed andbeyond

33KV,SF6

gascircui tbreakersarepreferred. Thereare1nainlytwotypesofcircui tbreakersusedforanysubstations.Theyare (a) SF6circuitbreakers, (b) Vacuumcircui tbreakers .

DEPTOFEEE,SKIT.

Page1 9

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

4.6.1 SF6CircuitBreakers Sulphurhexafluoride(SF6)isaninett,heavygashavi nggooddielectticandarcextinguishingpr opetties.Thedielectricstrengthofthegasincreaseswithpressureandismorethanthedielectticstrengtho foilat3kg/cm2.SF6isnowbei ngwidelyusedinelectricalequi pmentlikehighvoltagemetalenclosedc ables;highvol tagemetalcladswitchgear,capacitors,circuitbreakers,currenttransformers,bushings, etc.Thegasisliquefiedatcertai nlowtemperature,liquidificationtemperatureincreaseswi ththepress ure. SomeofthepropettiesofSF6are, );>-

Veryh igh dielectric strength

);>-

High thermalandchetnicalinertia

"

Supetiorarcextingui shingcapability

);>-

Lowdeco1nposition by arcing

4.6.2 VacuumCircuitBreakers Vacuum typeofcircuit

breakersisused forsmall

KV rated stationsbelow33KV.

Theyareonlyusedinlowdisttibutionside.

4.6.3 NamePlateDetailsof132KVSF6C

B

:200-SFM-40A

Type

:145KV

RatedVoltage

:650KV(Peak)

LightiningImpulseWithstandRated

:SOHZ

Frequency

:1600A

NormalCurrent RatedShottCircuitBreakingCll!TentSym mettical Asymmettical RatedShottCircuitMakingCurrentO ut-Of-PhaseBreaki ngCurrent RatedBreak Time

:31.SKA :37.2KA :80KA(Peak) :7.9KA :60ms(3Cycles) :40KAFor3Sec

RatedShottTimeCurrent

DEPTOFEEE,SKIT.

Page2 0

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

OperatingSequenceTotal

:0-0.03s-C0-3min-CO

MassOFSF6Gas

:8.7kg

SF6GasPressureAT20c,l013hpaTot

:6.3bar

alMassOfTheCircujtBreakerRefer

:l300kgI EC-56

enceStandard

4.6.4 NamePlateDetailsof33KVVacuumC

B

:36KV

VoltageFrequen cyNormalCtuTe nt

:50HZ :800A :25KA

SYMBreakingCapacity ShortTi1neCurrentD

:25KA

uration

:3sec

Maki ngCapacity

:63KA(peak)

P.FWithstand

:70KV

Impulse

:l70KV(peak)

ShuntTripcoilSpring

:220VDC

RELCoilTotalWeigh

:220VDC

tOperatingSequence

:2000kg

Type

:0-3MIN-C0-3MIN-CO :VN363AF

4.7

BUS Thebusisalineinwhichtheincomingfeederscomeintoandgetintotheinsttu mentsforfurtherstep

uporstepdown .Thefirstbusisusedforputtingtheincomingfeedersinlasingleline.Theremaybedoubleline inthebussothatifanyfaultoccursintheonetheothercanstillhavethectuTentandthesupplywillnotstop.Thet wolinesinthebusareseparatedbyalittledistancebyaconductorhavingaconnectorbetweenthem.Thisissot hatonecanworkatatimeandtheotherworksonlyifthefirstishavinganyfault.

DEPTOFEEE,SKIT.

Page2 1

OPERATI ONANDMAINTENANCE OF132/33KVSUBSTATION

4.8

TRANSFORMERS Transformerscomeinarangeofsizesfromath umbnail-

sizedcouplingtransformerhiddeninsideastage1nicrophonetohugeunitsweighinghun dredsoftons

used

tointerconnectportionsofnationalpowergrids.Alloperatewi ththesamebasicprinciples,althoughtherangeof designsis wide .Whilenewtechnologieshaveeliminatedtheneedfortransformersinso1neelectroniccircuits,transform ersarestillfoundinnearl yallelectronic devicesdesignedforhousehold ("mains") are

essential

voltage. Transfonners

forhighvoltagepowertrans1nission,whichmakeslongdistancetransmissioneconomically

practical.

Fig:4.8.1ElectricalTransformer. 4.8.1 BasicPrinciple Thetransfo1merisbasedontwopri nciples:firstly,thatanelectJicctuTentcanproduce amagneticfield(electromagnetism)andsecondlyth atachangi ngmagneticfieldwi thi na

coilof

wireinducesa voltage across the ends of the coil(electromagneticinduction).

Changingthecu1Tentintheprimarycoilchan gesthemagneticfluxthatisdeveloped. Thechan ging1nagneticfluxinducesavoltageinthesecondarycoil.

DEPTOFEEE,SKIT.

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OPERATIONANDMAINTENANCEOF132/33KVSUBSTATI ON

-.......:\..

...._..,.,.

·,,,......, · •+

' I

.:i.

--'

,,,.,,

""I

•

,

· •

'

·I='

-•-.

·•

I

•

.

,' _,.,._..,

-

I

-·-

..

i.

-..-

.·--..... '"·l

-·· •

_ _ ,,, •

)

'

I

c..,,.

Fig:4.8.1.1IdealTransformer. Anidealtransformerisshownintheadjacentfigtu-e;Currentpassingthroughthepri mary coilcreates a

magnetic

field .

The

primary

and

secondarycoils

arewrappedaroundacoreofveryhighmagneticpermeability,suchasiron,sothatmostofthe1nagneticfluxpass esthroughbothpri maryandsecondarycoils.

4.8.2 Inductionlaw

ThevoltageinducedacrossthesecondarycoilmaybecalculatedfromFaraday'slawofinduction, whichstatesthat,wh ereVSistheinstantaneo usvoltage,NSisthentu-nberofturnsinthesecondarycoiland equalsthemagneticfluxthroughonetu1nofthecoil.Iftheturnsofthecoilareorientedperpendiculartothem agneticfieldlines,thefluxistheproductofthe1nagneticfieldstrengthandtheareaAthroughwh ichitcuts.T heareaisconstant ,bei ngequaltothecrosssectionalareaofthetransformercore,whereasthemagneticfieldvarieswi thti meaccordingtotheexcitatio nofth epri1nary.

DEPTOFEEE,SKIT.

Page21

OPERATIONANDMAINTENANCEOF132/33KVSUBSTATI ON

's=

-=

Vs Vp

Ns N,p

Ip I

rP

Vp sV s Vp

NP N:>

tl

Np

s -NNp

Fig:4.8.2.1MutualInduction.

DEPTOFEEE,SKIT.

Page22

OPERATIONANDMAINTENANCEOF132/33KVSUBSTATI ON

Sincethesa1nemagneticfluxpassesthroughboththepri maryandsecondarycoilsinanidealtransfonne r,theinstantaneousvoltageacrossthep1imarywindingequalsTakingtheratioofthetwoequationsforVSandVP givesthebasicequationforsteppinguporsteppingdownthevoltageIdealpowerequationTheidealtransfonner asacircuitele1nent.

Ifthesecondarycoilisattachedtoaloadthatallowscurrenttot1ow,electricalpoweristransmittedfromth eprimarycircuittothesecondarycircui t .Ideally,thetransformerispe1fectlyefficient;alltheincomi ngenergyis transformedii-omthe primarycircuittothemagneticfieldandintoth esecondarycircuit.Ifthisconditionismet ,theincomingelectJic powermustequaltheoutgoingpo wer.

GivingtheidealtransformerequationTransfo1mersareefficientsothisfo1mulaisareasonableapproxi mation .Ifthevoltageisincreased,thenthecutTentisdecreasedbythesamefactor.IfanimpedanceZSisattached acrossthetermi nalsofthesecondarycoil,itappearstothepri1narycircuittohaveanimpedanceofZS =(VSIS).

Fig: 4.8.2.2ThreePhaseSOMVAAutoTransformer.

DEPTOFEEE,SKIT.

Page23

OPERATIONANDMAINTENA NCEOF132/33KVSUBSTATI ON

4.8.3Specificationsof132KV/33KVA utoTransformer RatedMVAN oofphases Insulationlevel

: 50MVA :3 :HV LI900AC395 :HV N LI95AC38 IVL LI550AC230 V LI170AC70

TypeofcoolingR atedMVA RatedKVatnoload

ONAN

:H VI VL V

LineAmperes

:HV IV LV

TemperarureRiseoC A vg.WOO Impedancevolts NormalTapconditions)

:Topoil

DNAF 75 100 220KV -132KV 11KV --

196.8 262.4 328.0 437.4 1299.0 1732.1

- 50oC 550CH V-IV 7.667 HV-LV 24.55 IV-LV 17.69

10.222 32.72 23.59

4.9 CAPACITOR BANK ATTACHED TO THE BUS Thecapacitorbanksareusedacrossthebussothatthevol tagedoesnotgetdowntillattherequirepla ce.Acapacitorbankisusedintheoutgoi ngbussothatitcan1naintai nthevoltagelevelsameintheoutgoingf eeder.

DEPTOFEEE,SKIT.

Page24

OPERATIONANDMAINTENA NCEOF132/33KVSUBSTATI ON

Fig:4.9.1CapacitorBankInTheDistributionSystem.

DEPTOFEEE,SKIT.

Page25

OPERATIONANDMAINTENA NCEOF132/33KVSUBSTATI ON

4.9.1CapacitorControlIsUsuallyDoneToAchieveTheFollowingGoals );:>-

Reducelossesduetoreactiveloadcurrent;

);:>-

Reduce KV Ademand,decreasecustomerenergyconstunption,

);:>-

Improvevoltageprofile,andincreaserev enue.

);:>-

Indirectly capacitor control also results

in longer equjpment lifetimes

becauseofreducedequjpment stresses.

Experienceshowsthatswitchedfeedercapacitorsproducesomeofthefastestrettunsonequipmentinvest1nentSourcesofEnergyLoss.Energ ylossesintransmissionlinesandtransformer sareoftwoki nds:resistiveandreactive.Thefotmerarecausedbyresistivecomponentoftheloadandcann otbeavoided.Thelatter,comin gfromreactivecomponentoftheload ,canbeavoided.

P.e 1ctinl..o!!ES

He:ny [ruluctive load

Substation

No eadruelesses

-• Fig:4.9.1.1ReactiveLosses.

DEPTOFEEE,SKIT.

Page26

OPERATIONANDMAINTENA NCEOF132/33KVSUBSTATI ON

5.1TRANSFORMERPROTECTION );>- StationTransfo1mer:HGFuseprotection

onHYsideandfuseprotectiononLVsideandV entpi pe . );>-

Powertransformersupto7.5MVA: HYside:OIL&DirectionalEILprotectionwi thh ighestelementinOILrelays. LY

side: OIL & E/L RelayOTIandWTI

protection

Buchholz

Relay

OLTC

Buchholz

);>-

Powertransfotmersfrom8.0MVAandabove:HYsideOIL&DirectionalE/Lprotectionwith highsetelementinOIL

relays .

LY

side

OIL&E/Lprotection:differentialprotectionBuchholzRelayOLTCBuchholzRelayOTI,W TIandPRY. );>-

Powertransfonnersii-om31.SMVAandabove:Overfluxprotection

&LYWTIinadditiontoprotection.

5.2FEEDERPROTECTION );>-

33KV wi th

feeders: highest

Non directional OIL &EIL and IDMTcharacteristics.

protection

);>-

132KVfeeders:Mainprotection:Distanceprotection.Backupprotection:DirectionalO/L&E/Lp rotection. );>-

DEPTOFEEE,SKIT.

220KVfeeders:Mai n-1protection: DistanceprotectionMain-2protection: Distanceprotection,LBB protection, pole d.iscrepanc yRelay.

Page27

OPERATI ONANDMAINTENANCEOF132/33KVSUBSTATION

5.3 IMPORTANT POINTS BE KEPT IN VIEW WHILE LAYINGOUTTHESUBSTATION

TO

Substationsarei1nportantpaitofpowersystem .Thecontinui tyofsuppl ydependstoaconsiderabl eextentuponthesuccessfuloperationofsub-stations.Itis,therefore,essentialto

exerciseutmostcai-

ewhiledesigni ngandbuildingasubstation .

Thefollowingai·etheimportantpointswhichmustbekept inviewwhilelayin goutasubstation: )>Itshouldbelocated

atapropersite.Asfai·aspossible,itshouldbelocatedatthe centt-eofgravit yofload .

)>-ItshouldprovidesafeandreliableaJTangement.Forsafety,consideration1nustbe

giventothemaintenanceof1egulationclearances,facilitiesforcaiTyingoutrepairsandmaintenance,abnormaloccurrence ssuchaspossibilityofexplosionorfit-eetc. Forreliability,consideration tnust be given forgood design and construction, theprovisionofsuitableprotectivegeai·etc. )>-

Itshouldbeeasilyoperatedandmaintain ed.

)>-

It

should

DEPTOFEEE,SKIT.

involve

1n1111mum

capital

cost

Page28

OPERATI ONANDMAINTENANCEOF132/33KVSUBSTATION

CONCLUSION Transmission and distribution stations exist at v a r i o u s scales throughout a powersystem. In general, they are present an intetface between different levels or sections of the powersystem, with the capability to switch or reconfigure the connections amon g v arious trans1nission and disttibution lines. The major stations include a control room ti-om which operations are coordi nated . Smaller disttibution substations follow the same ptinciple of receiving power at higher vol tage on one side and sendin g out a number of distribution feeders at lower voltage on the other, but they serve a more limited local area and are generally unstaffed. The central component of the substation is the transfotmer, as It provides the effective inenface between the high and low-voltage parts of the system . Other crucial components are circuit breakers and switches. Breakers serve as protective devices that open automatically in the event of a fault, that is, when a protective relay indicates excessive cu1Tent due to some abnormal condition. Switches are control devices that can be opened or closed deliberately to establish or break a connection. An impottant difference between circui t breakers and switches is that breakers are designed to inte1Tupt abnormally high currents (as they occur only in those very situations for which circuit protection is needed), whereas regular switches are designed to be operable under normal cu1Tents. Breakers are placed on both the high and low-voltage side of transformers. Finally, substations may also include capacitor banks to provide vol tage support

DEPTOFEEE,SKIT.

Page29