Dedicated Onsite Condition Monitoring ofHigh Voltage Power Cables震荡波法检测高压电缆局放.docx

Dedicated Onsite Condition Monitoring ofHigh Voltage Power Cables震荡波法检测高压电缆局放.docx

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DedicatedOnsiteConditionMonitoringofHighVoltagePowerCables震荡波法检测高压电缆局放

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Abstract--Foradvanced,non-destructiveon-siteconditionmonitoringofHVpowercablesupto150kVbypartialdischargedetectionanddielectriclossesmeasurementitisnecessarytoenergizethedisconnectedcablesystem.OneofthemethodsavailableforthispurposeisbasedonapplyingdampedACvoltagesupto150kV.Inthispaper,theuseofmoderntechnologicalsolutionsinpowerelectronicsandsignalprocessingaswellasintechnicaldesignandproductionmethodswillbediscussedonthebasisofultralightsystem（300kgwhichisabletotestcablesupto20kmlengths.

IndexTerms—dampedACvoltages,diagnosis,dielectriclosses,HVpowercables,localization,on-site,partialdischarges.I.INTRODUCTION

heinsulationfailuresinacablenetworkmaybecausedbylowerdielectricstrengthduetoagingprocessesandbyinternaldefectsintheinsulationsystem.Itisknownthatunlikevoltagetesting,measurementsofthedielectricmaygiveanabsoluteindicatorforthequalitylevelofthecableinsulation.ForHVpowercablesdifferenton-siteinspections/diagnosticsareavailable[1,2].Inparticularwithregardtoinformationasprovided,conclusionsaboutshort-andlong-termconditioncanbemade（figure1.

Theresultsofthesemeasurementsmayhaveadirectrelationtotheaveragequalitativeleveloftheinsulationatthemomentofmeasurementandcanthusbeappliedasatrend-orfingerprintmeasurementduringfutureinspections.Itfollowsfromfigure1thatpartialdischargediagnosisanddielectricdiagnosismayplayimportantroleinshort-andlong-termconditionassessment,figure2.

cableconnection.Inordertorunthemeasurementpartialdischargesareignitedinthecableinsulationorjointsbytheapplicationofatestvoltage[3].TheoccurrenceofpartialdischargeshavephysicalcharacteranditisdescribedbysuchimportantparametersasPDinceptionvoltage,PDpulsemagnitudes,PDpatternsandPDsitelocationinapowercable.ForutilitiesinterestedinapplyingPDdiagnosticsforE.GulskiiswithDelftUniversityofTechnology,TheNetherlands

（e.gulski@tudelft.nl

P.P.SeitziswithSeitzInstrumentsAG,Switzerland（pps@seitz-instruments.ch

B.QuakiswithSeitzInstrumentsAG,Switzerland,（bq@seitz-instruments.ch

F.PetzoldiswithSebaKMT,Germany（petzold.f.@

F.deVriesiswithNuonTecno,Alkmaar,TheNetherlands

（frank.de.vries@

parametersareofimportance.

Inparticular,analyzingPDparametersfordifferenttypesofcableinsulationandcableaccessoriescanresultindevelopingexperiencenorms[4,5].SuchnormswouldveryhelpfulindevelopingknowledgerulestosupportAMdecisions.

ofthelossfactoroftheinsulationmaterial[3,4].Thisfactorincreasesduringtheageingprocessofthecable.Thetanδmeasurementshouldberegardedasadiagnosticand/orsupportingmeasurement.Inpractice,inHVinsulationisknownthatinadditiontoabsolutevalueoftanδatcertaintestvoltagealsotheincrementoftandeltaasmeasuredattwo

DedicatedOn-siteConditionMonitoringofHighVoltagePowerCablesupto150kVE.Gulski,SeniorMember,IEEE,P.P.Seitz,B.Quak,F.Petzold,FrankdeVries

T

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conditionassessment.Thelosstangentismeasuredasfunctionofvoltagetocheckthequalityofimpregnation.Thetan

δ

v

alueofacableisstronglyinfluencedbythe

compositionoftheconnection,thetrace,andthedeviationsinjointsandtheactualmeasurementisonlyapplicableastrendmeasurementifcompositioncircumstancesofthetraceandthermalconditionsofsuccessivemeasurementsarevirtuallyidentical.ForHVpaperinsulatedcablesthetanδcanbeanimportantindicatorofpossiblethermalbreakdowns[4].

II.ON-SITEENERGIZINGOFHVPOWERCABLES

orcompleteon-sitediagnosisoftransmissionpowercablesbyPDdetectionanddielectriclossesmeasurementitisnecessarytoenergizethedisconnectedcablesystem[8,9].Thedetectionandmeasuringequipmentisthereforedirectlyconnectedtothecableconductors（orthroughtheswitchgear.Inthisway,thedifferentphasesofthecablecircuitcanbeenergizedandthePDpulsescanbecoupledout.ThecapacitivepowerP=2π•f•Ccable•U2testneededtostresson-sitethecableinsulationisdeterminedbythetestfrequencyf,thecablecapacitanceCcableandthetestvoltageUtest.Inordertodecreasethecapacitivepowerdemandsforenergizingcablesascomparedto50Hztestvoltages,differentenergizingmethodsusingspecificvoltageshapedandfrequencieshavebeenintroducedforPDdiagnosticsnowadays[11,15,16].Asshownin[3,16,17]duetoseveralimportantcharacteristicssuchas

1.ACvoltagetypeequivalenceinPDinceptionprocesses

forsolidinsulatingmaterials,

2.non-destructivenessofvoltagestressduringthediagnosis,3.real-timeadvancedanalysisofdiagnosticdata,

4.sufficientimmunityforon-siteinterferencesandlow

levelofsystembackgroundnoise,

5.IEC,IEEEstandardsconformity[2,3,4,12,13],

6.testcostefficiencybasedoninvestmentandmaintenance

costs,transportabilityandoperationofthemethodindifferentfieldcircumstances,

theuseofpartialdischargesanddielectriclossesdiagnosisatdampedACvoltages（DAChasbecomeimportantsolutionforon-sitetestinganddiagnosisofHVpowercables（figures3,4.

Togenerateon-sitedampedACvoltagesupto150kVpeakandtoperformadvanceddiagnosisbymeaningfulPDparametersmodularhardware/softwaresolutionhasbeendeveloped（figure4.Inparticular,byuseof

-modernsolid-statetechnologyandlaser-control

techniques（HVSolid-StateSwitch,

-powerelectronics,digitalsignalprocessing（HVSolid-StateSwitch,HVsource,

-digitalsignalprocessingandfiltering（PDdetector,

-

wirelesscommunicationandembeddedcomputersystem（PDdetector,Controlunit,PDanalyzer

novelsystemOWTSHV-seriestype150hasbeendevelopedforon-sitePDdiagnosisofHVpowercablesupto150kV（table1.

III.DAMPEDACVOLTAGEGENERATION

orthegenerationofdampedAC（DACvoltages,thepowerdemandislowduetothechargingthecablecapacitance（figure5withacurrentof10mAanda

F

TABLEI

MAXIMUMTESTVOLTAGESOFA150KVTESTSYSTEM

Networkvoltage[kV]OWTSHV150[xU

]

F

150kVSwitch

150kV/7.1HControlHVDivider

HVPowerCable

150kVHVSource

InductorUnit

Unit

PDAnalyzer

PDcouplingcapacitorPDDetector

（a

（b

Fig.4:

Examplesofon-sitetestinganddiagnosisofHVpowercablesusingdampedACtestsystem150kV:

aafterinstallationinsubstationduringtestinga9.6kmlong50kVoil-filledcable,

bafterdisassemblingpreparedfortransportation（weight300kg

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capacitance（representedasacapacitanceCcisswitchedbySinserieswithlargeinductanceL,resultinginansinusoidaldampedACvoltageformwithafrequencybetween20HzandfewhundredsofHz（figure6Inparticular,thecablesampleislinearlychargedwithcontinuouslyincreasingHVvoltage,directlyfollowedbyaswitchingprocessandperiodofseveralsinusoidalACcycles,figure7.Asaresult,duringthechargingtimeno‘‘steadystate’’DCconditionsoccurinthecableinsulation[14].Assoonasthecableischarged,theHVsupplyisdisconnectedandaspeciallydesigned150kVsolid-stateswitchconnectsthecablesampleCctoanair-coreinductorL=7.1Hinaclosuretimeoflessthan1μs.Inthisway,andLCloopiscreatedandanoscillatingvoltagewaveisappliedtotestthesample.

Thetestfrequencyoftheoscillatingvoltagewaveisapproximatelytheresonantfrequencyofthecircuit:

f⋅=π21ThismeansthatthetestfrequencyoftheappliedDACvoltageisdependentonthecablecapacitance,seefigure6.TheHVpowercablecapacitancevariesduetoparameterslikethe

cross-sectionoftheconductorandthethicknessandthetype

oftheinsulation.Intable2examplesareshownfordifferent

typesofHVcablesandcablelengthandthedampedAC

frequenciestobegeneratedusingsystemasshowninfigure2.

Duetothelowlossfactoranddesignoftheair-core,the

resonantfrequencyisclosetotherangeofpowerfrequencyoftheservicevoltage:

20Hzto300Hz.

ThequalityfactorQCoftheresonantcircuit,whichisresponsiblefortheattenuationoftheoscillations,canbeexpressedby:

QC=√（L/（C*RA2

HereisRAtheequivalentcircuitresistance.ThequalityfactorQoftheresonantcircuitremainshighdependinguponcable（30tomorethan100,asaresultoftherelativelowdissipationfactorofpowercables.Aslowlydecayingsinusoidalwaveform（decaytimeupto0.3secondisappliedastestvoltagetoenergiesthecablesample.

IV.SYSTEMosupportefficienton-sitetestinganddiagnosisbasedonfieldexperiencesthefollowinghardware/softwaresolutionshavebeendeveloped（figure8.150kVHVSource:

toloadthepowercablecapacitance

150kVHVDCvoltagesupplyisusedwithacircuiteffectiveloadcurrentof10mA.DuringchargingthetestobjectthelinearandcontinuouslyincreasingHVvoltageiscontrolledby

thecomputer.Infigure5thechargingtimeinfunctionoftheloadcapacitiesisshown.Theswitchingdischargecurrentof

TABLEII

EXAMPLESOFTYPICALDAMPEDACVOLTAGEFREQUENCIESFORDIFFERENTLENGTHSOFTWOTYPICAL150KVPOWERCABLES

Length[km]XLPE（C=154pF/m

[Hz]

Oilfilled（C=373pF/m

[Hz]

T

thepowersupplyarelimitedby15kΏseriesresistortomax.16A.

150kVHVsolid-stateswitch:

Thefunctionofthe150kVswitchistoestablishaseriesresonancecircuitbetweenchargeHVpowercablecapacitanceandtheairinductorL.AsaresultsinusoidaldampedACvoltagesmayoccurinthecablesample.Theswitchisper