Fault Location and Incipient Fault Detection in Distribution Cables
Fault Location
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Transcript of Fault Location
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PRESENTED BY
ER IK SCHELLENBERGIDAHO POWER
FaultLocating
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Topics
ImpedanceBased ReactanceMethod TakagiMethod ModificationstoTakagiMethod TWS&DoubleEndedNegativeSequence
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OneLine
EquivalentTheveninSources Bus Line RelaywithCT&CCVT
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RadialLine
Applyafaultmdistancedownaradialline
misapercentage oftheline.Forexampleifthefaultis25%fromBusSthen(1m)yields75%,foratotallineimpedance,ZL ,of100%
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V/I=mZL (sometimes)
UsingohmslawthefaultlocatoratScancalculatetheimpedance,(mZL),thatthevoltageVisbeingdroppedacrossforthreephaseboltedfaults.
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V/ICalculation
TheequivalentcircuitwithrespecttoBusSclearlyshowsthatthemeasuredvoltageVisbeingdroppedacrosstheportionofthetransmissionlinetothefaultpoint.
(m)ZL =V/I(Ohms)
(V/I)ZL
m= (%)
FaultLocation=m(LineLength)(miles)
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V/I&FaultResistance
Assumethefaulthassomeresistance,Randthetransmissionlineispurelyinductive.
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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
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V/ILimitations
Usingohmslawdirectlyasfaultlocatorisimpracticalforavarietyofreasons.Someoftheseinclude:
Onlyworksonthreephasefaults Onlyworksonradiallines Onlyworksonboltedfaults ImpactedbyLoad
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SimpleReactanceMethod
Transmissionslineimpedance,Z,istypicallydominatedbythereactivecomponent,X.
Faultimpedanceistypicallydominatedbytheresistivecomponent,R.
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FaultResistance&ReactanceMethod
Letslookattheradialexamplewithfaultresistanceagain.
Theforwardvoltagedropmeasuredbythefaultlocatoris Vs =mZL(Is)+Is(RF)
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MinimizetheEffectofRFusingReactance
DividebythemeasuredcurrentIs
Retainonlytheimaginarycomponentofeachquantity
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ReactanceMethodwithRemoteSource
Nolongeristhesystemradial
ThecurrentflowingthroughRF isnowthesumofthelocalsource,Is,andtheremotesource,IR
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SameReactanceTechnique:NowwithIR
Writetheforwardvoltagedropequation,
DividebyIs tocalculateameasuredImpedance,
Taketheimaginarycomponentofeachtermtomitigatefaultresistance,
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HomogenousSystem&Reactance
IfyouhaveahomogenoussystemthenbothIS andIR willhavethesameangleandtheimaginarypartof(If/Is)Rf iszero.
Is
IRIf=IS+IR
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NonHomogenousSystem&Reactance
IS andIR willnothavethesameangleandtheimaginarypartof(If/Is)Rf willshowupinthefaultlocationcalculationasanerrorterm.
lS
lR
lf
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SimpleReactanceSummary
ThesimplereactancemethodwasanimprovementoverthestraightOhmsLawcalculationbutitstillhassomedrawbacks:
ImpactedbyLoad Nonhomogenoussystemsintroduceerrorinfaultresistanceterm
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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.
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Superposition
ThekeytotheTakagimethodistheideaofsuperposition
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Load PureFaultNetwork
CompositeFaultNetwork
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TakagiLocal&RemoteCurrent
CompositeFaultNetwork PureFaultNetwork
Voltageequationforthelefthandside Voltageequationfortherighthandside
BothequationsequalVF.SettheLeftsideequaltotherightside
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NoFaultCurrentinLoadCircuit
If =If becausethereisnofaultbranchcurrentinthepureloadstate
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Load PureFaultNetwork
CompositeFaultNetwork
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TakagiFaultCurrent
FromthepreviousslidewecalculatedIR intermsofIS
PlugintoIF equation
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ForwardVoltageDrop&Takagi
Fromthepreviousfaultlocationalgorithmswedevelopedtheforwardvoltagedropequationwithrespecttofaultlocator:
Pluginournewequationforthefaultbranchcurrent,If:+
=
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PauseforError
willbezeroifthenumeratoranddenominatorhavethesamephaseangle,(homogeneoussystem)
Ifthereisloadflowonthesystem willbenonzerobutifthemagnitudeoffaultdutyismuchgreaterthanload,theangle willapproachzero.
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TakagiDistance
Ifwe:MultiplybythecomplexconjugateofIs, Taketheimaginarypartoftheequationtoeliminatefaultresistance, Assumethesystemistotallyhomogeneous,andfinally Solveform
Wewillgetthefollowingequation:
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Zero&NegativeSequenceTakagi
TheTakagicanusethezerosequencetermforgroundfaults,eliminatingtheneedforprefaultdata
Thenegativesequencecanalsobeused
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MutualCoupling
Thereismagneticcouplingbetweenphasesonacurrentcarryingtransmissionline,Zm.
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MutualCoupling
Applyaboltedfaultsomelengthmdowntheline.
Avoltageisinducedineachphasethroughthemutualcoupling.HereZm iswrittenexplicitlyasZab andZac.
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VoltageEquation
Theforwardvoltagedropequationforthefaultedphaseis
Adding&Subtractingthesamequantity0
Gatheringterms
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VoltageEquationContd
RecognizethatIa+Ib+Ic istheresidualorzerosequencecurrent
Zm isadifficultquantitytohandledirectly.ThroughtheuseofSymmetricalComponenttheoryitcanbeshownthat:
SolvingforZs intheZL0 equationandpluggingthisintotheZL1 equationyieldsaZm thatisequalto:
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Va andthemysteriousk
Va isnowexpressedintermsofpositiveandzerosequencelineparameterswhichcanbeloadedintoarelayassettings
FactoroutmZL1,(thedistancetothefault)
Definektomaketheequationprettier
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ModifiedTakagi
OnceagaintaketheimaginarycomponentofbothsidesandsolveformZL1
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TwoTerminalMethods
Moreaccuratethansingleendedmethods
Minimizes/Eliminateseffectsof FaultResistance Loading LineChargingCurrent
Moreoverhead.Datamustbegatheredorsharedfrommultiplelocations
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TravelingWave
Afaultwillcauseatransienttopropagatealongthelineasawave
Thewaveisacompositeoffrequencieswithafastrisingfrontandslowerdecayingtail
Thewavestravelatnearthespeedoflightandeventuallydecay
Bytimetaggingthewavefrontsastheycrossbothterminalsaveryprecisefaultlocationcanbecalculated
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WavePropagation
Thewavesleavethedisturbedareatravelingatthevelocityofpropagationwhichisalittlelessthanthespeedoflight
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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.
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DoubleEndedNegativeSequence
ByusingthenegativesequencemethodologyproposedbySELthefollowingsourcesoferroraremitigated:
Prefault load Zerosequencemutualcoupling Zerosequenceinfeedfromlinetaps FaultResistance
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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