Fault Location

PRESENTED BY

ER IK SCHELLENBERGIDAHO POWER

FaultLocating

Topics

ImpedanceBased ReactanceMethod TakagiMethod ModificationstoTakagiMethod TWS&DoubleEndedNegativeSequence

OneLine

EquivalentTheveninSources Bus Line RelaywithCT&CCVT

RadialLine

Applyafaultmdistancedownaradialline

misapercentage oftheline.Forexampleifthefaultis25%fromBusSthen(1m)yields75%,foratotallineimpedance,ZL ,of100%

V/I=mZL (sometimes)

UsingohmslawthefaultlocatoratScancalculatetheimpedance,(mZL),thatthevoltageVisbeingdroppedacrossforthreephaseboltedfaults.

V/ICalculation

TheequivalentcircuitwithrespecttoBusSclearlyshowsthatthemeasuredvoltageVisbeingdroppedacrosstheportionofthetransmissionlinetothefaultpoint.

(m)ZL =V/I(Ohms)

(V/I)ZL

m= (%)

FaultLocation=m(LineLength)(miles)

V/I&FaultResistance

Assumethefaulthassomeresistance,Randthetransmissionlineispurelyinductive.

SimplifiedV/IwithsomeR

LetIs =100A,XL =10,&RF =5 VLINE =100(1090)=10090V VF =100 (50)=500V Vs =VLINE +VF =11263V Distance=VS/IS=1163 mZLDistance

Is

Vs =VLINE+VF

VF

VLINE

XL

RF

Distance

V/ILimitations

Usingohmslawdirectlyasfaultlocatorisimpracticalforavarietyofreasons.Someoftheseinclude:

Onlyworksonthreephasefaults Onlyworksonradiallines Onlyworksonboltedfaults ImpactedbyLoad

SimpleReactanceMethod

Transmissionslineimpedance,Z,istypicallydominatedbythereactivecomponent,X.

Faultimpedanceistypicallydominatedbytheresistivecomponent,R.

FaultResistance&ReactanceMethod

Letslookattheradialexamplewithfaultresistanceagain.

Theforwardvoltagedropmeasuredbythefaultlocatoris Vs =mZL(Is)+Is(RF)

MinimizetheEffectofRFusingReactance

DividebythemeasuredcurrentIs

Retainonlytheimaginarycomponentofeachquantity

ReactanceMethodwithRemoteSource

Nolongeristhesystemradial

ThecurrentflowingthroughRF isnowthesumofthelocalsource,Is,andtheremotesource,IR

SameReactanceTechnique:NowwithIR

Writetheforwardvoltagedropequation,

DividebyIs tocalculateameasuredImpedance,

Taketheimaginarycomponentofeachtermtomitigatefaultresistance,

HomogenousSystem&Reactance

IfyouhaveahomogenoussystemthenbothIS andIR willhavethesameangleandtheimaginarypartof(If/Is)Rf iszero.

Is

IRIf=IS+IR

NonHomogenousSystem&Reactance

IS andIR willnothavethesameangleandtheimaginarypartof(If/Is)Rf willshowupinthefaultlocationcalculationasanerrorterm.

lS

lR

lf

SimpleReactanceSummary

ThesimplereactancemethodwasanimprovementoverthestraightOhmsLawcalculationbutitstillhassomedrawbacks:

ImpactedbyLoad Nonhomogenoussystemsintroduceerrorinfaultresistanceterm

TakagiMethod

In1979ToshioTakagiandYukinari Yamakoshi filedforaU.S.Patentforanewsingleendedfaultlocatingmethod.

In1982Takagi,etal.delivertheirpaper.

T.Takagi,Y.Yamakoshi,M.Yamaura,R.Kondow,T.Matsushima,DevelopmentofaNewTypeFaultLocatorUsingtheOneTerminalVoltageandCurrentData,IEEETransactionsonPowerApparatusandSystems,Vol.PAS101,No.8,August1982.

Superposition

ThekeytotheTakagimethodistheideaofsuperposition

+

Load PureFaultNetwork

CompositeFaultNetwork

TakagiLocal&RemoteCurrent

CompositeFaultNetwork PureFaultNetwork

Voltageequationforthelefthandside Voltageequationfortherighthandside

BothequationsequalVF.SettheLeftsideequaltotherightside

NoFaultCurrentinLoadCircuit

If =If becausethereisnofaultbranchcurrentinthepureloadstate

+

Load PureFaultNetwork

CompositeFaultNetwork

TakagiFaultCurrent

FromthepreviousslidewecalculatedIR intermsofIS

PlugintoIF equation

ForwardVoltageDrop&Takagi

Fromthepreviousfaultlocationalgorithmswedevelopedtheforwardvoltagedropequationwithrespecttofaultlocator:

Pluginournewequationforthefaultbranchcurrent,If:+

=

PauseforError

willbezeroifthenumeratoranddenominatorhavethesamephaseangle,(homogeneoussystem)

Ifthereisloadflowonthesystem willbenonzerobutifthemagnitudeoffaultdutyismuchgreaterthanload,theangle willapproachzero.

TakagiDistance

Ifwe:MultiplybythecomplexconjugateofIs, Taketheimaginarypartoftheequationtoeliminatefaultresistance, Assumethesystemistotallyhomogeneous,andfinally Solveform

Wewillgetthefollowingequation:

Zero&NegativeSequenceTakagi

TheTakagicanusethezerosequencetermforgroundfaults,eliminatingtheneedforprefaultdata

Thenegativesequencecanalsobeused

MutualCoupling

Thereismagneticcouplingbetweenphasesonacurrentcarryingtransmissionline,Zm.

MutualCoupling

Applyaboltedfaultsomelengthmdowntheline.

Avoltageisinducedineachphasethroughthemutualcoupling.HereZm iswrittenexplicitlyasZab andZac.

VoltageEquation

Theforwardvoltagedropequationforthefaultedphaseis

Adding&Subtractingthesamequantity0

Gatheringterms

VoltageEquationContd

RecognizethatIa+Ib+Ic istheresidualorzerosequencecurrent

Zm isadifficultquantitytohandledirectly.ThroughtheuseofSymmetricalComponenttheoryitcanbeshownthat:

SolvingforZs intheZL0 equationandpluggingthisintotheZL1 equationyieldsaZm thatisequalto:

Va andthemysteriousk

Va isnowexpressedintermsofpositiveandzerosequencelineparameterswhichcanbeloadedintoarelayassettings

FactoroutmZL1,(thedistancetothefault)

Definektomaketheequationprettier

ModifiedTakagi

OnceagaintaketheimaginarycomponentofbothsidesandsolveformZL1

TwoTerminalMethods

Moreaccuratethansingleendedmethods

Minimizes/Eliminateseffectsof FaultResistance Loading LineChargingCurrent

Moreoverhead.Datamustbegatheredorsharedfrommultiplelocations

TravelingWave

Afaultwillcauseatransienttopropagatealongthelineasawave

Thewaveisacompositeoffrequencieswithafastrisingfrontandslowerdecayingtail

Thewavestravelatnearthespeedoflightandeventuallydecay

Bytimetaggingthewavefrontsastheycrossbothterminalsaveryprecisefaultlocationcanbecalculated

WavePropagation

Thewavesleavethedisturbedareatravelingatthevelocityofpropagationwhichisalittlelessthanthespeedoflight

NegativeSequenceQuadratic

In1999Demetrios A.Tziouvaras,JeffRoberts,andGabrielBenmouyal ofSELintroducedanewdoubleendedtechniquethatusesthenegativesequencequantitiesfrombothterminalstofaultlocate.

D.A.Tziouvaras,J.B.Roberts,G.Benmouyal,NewMultiEndedFaultLocationDesignForTwo orThreeTerminalLines,presentedatCIGREConference,1999,http://www.selinc.com/techpprs/6089.pdf.

DoubleEndedNegativeSequence

ByusingthenegativesequencemethodologyproposedbySELthefollowingsourcesoferroraremitigated:

Prefault load Zerosequencemutualcoupling Zerosequenceinfeedfromlinetaps FaultResistance

References

T.Takagi,Y.Yamakoshi,M.Yamaura,R.Kondow,andT.Matsushima,DevelopmentofaNewTypeFaultLocatorUsingtheOneTerminalVoltageandCurrentData,IEEETransactionsonPowerApparatusandSystems,Vol.PAS101,No.8,August1982.

W.A.Elmore,ZeroSequenceMutualEffectsonGroundDistanceRelaysandFaultLocators,Proceedingsofthe19thAnnualWesternProtectiveRelayConference,Spokane,WA,October1992.

E.O.SchweitzerIII,EvaluationandDevelopmentofTransmissionLineFaultLocatingTechniquesWhichUseSinusoidalSteadyStateInformation,Proceedingsofthe9thAnnualWesternProtectiveRelayConference,Spokane,WA,October1982.

K.Zimmerman,andD.Costello,ImpedanceBasedFaultLocationExperience,Proceedingsofthe31stWesternProtectiveRelayConference,Spokane,WA,October2004.

J.Glover,MSarma,andT.Overbye,PowerSystemAnalysisandDesign,GlobalEngineering,2008.

W.Stevenson,andJ.Grainger,PowerSystemAnalysis,McGrawHillSeriesinElectricalandComputerEngineering,1994

HewlettPackard,TravelingWaveFaultLocationinPowerTransmissionSystems,ApplicationNote1285