外文翻译基于LabVIEW的电流互感器校验仪.docx

外文翻译基于LabVIEW的电流互感器校验仪.docx

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外文翻译基于LabVIEW的电流互感器校验仪

附录

ALabVIEWBasedInstrumentCurrentTransformerCalibrator

XinAiHalBaoY.H.Song

1）NorthChinaElectricPowerUniversity,Beijing,China107206

2）BrunelUniversity.UK

ABSTRACT

TheVirtualInstrument（VI）mainlyreferstobuildallkindsofinstrumentsbysoftwaresuchasLabVIEW,whichlikesarealinstrumentbuildinacomputer.Its'maincharacteristicsareflexibility,multi-functions,multipleusesforonePCcomputer,givinghighperformance,andislesscostly.Inthispaper,theVItechnologyisappliedtothetestandmeasurementofinstrumentcurrenttransformer（TA）.ByusingtheLabVIEW,theTAaccuracycalibratorwasdeveloped.ThisvirtualT.4calibratorcanautomaticallymeasuretheaccuracyofT.4andcanindicatetheratioerrorandphaseerrorcurves.ThetestsandcalibrationfortheTAshowthatthevirtualTAcalibratorcanbeusedinplaceofthetraditionalcalibratorandismuchbetterthanthetraditionalone.

Keywords：

Instrumentcurrenttransformer（TA）,TAcalibrator,VirtualInstruments,LabVIEW.

I.INTRODUCTION

Since1992theVXIbusRev.1.4standardwasestablishedbytheUnitedStatesandLabVIEWwaspresentedbytheNationalInstrumentsco.（Nl）,theVirtualInstrument（VI）havelainthefoundationforitscommercialuse.ThemaincharacteristicofVirtualInstrumentisthatitmakesinstrumentsbysoftware.MostofthetraditionalinstrumentcanbedevelopedbyVI.TheVIisarealinstrumentmadebythepersonalcomputer.

TheInstrumentcurrenttransformer（TA）iswidelyusedinallkindsofcurrentmeasurementandithasthefunctionsofprotection,isolationandextendingthemeasuringrange.Withtherapiddevelopmentofcomputermeasurementandcontroltechnology,andwiththesequentemergenceofcurrenttransformerandtransducer,thereisanincreasingnumberofcurrenttransformerswithhighaccuracyandlowsecondarycurrent.ThestandardTAsecondarycurrentisusually

1Aor5A:

somenon-standardTAsecondarycurrentmaybe01Aorlower.Althoughwehavethetechniquetomakethiskindofcalibratorbymeansofhardwaresuchassinglechipcomputerandelectroniccircuit,DSPandsoon,itwillcosttoomuchmoneyfortheseno-standardcalibratorandwilltaketoomuchtimeandthecalibratormadebythesehardwaremillnotbesatisfactoryinbothfunctionandpracticalityfordesigningallkindsofnewTA.

ThecalibratorthatadoptsVItechnologynotonlycanmeettherequirementsofthetraditionalonebutalsocansatisfycustomerswithsuchadvantagesasmulti-functions,convenience,andhighratiobetweenperformanceandcost.TheexperimentresultsindicatethatthevirtualcalibratorcanprovideexcellentconditionforTAmeasurementanddesign.TheVItechnologyandpersonalcomputermustbewidelyusedintheareaofcalibrationoninstrumenttransformer.

Ⅱ.THEWORKINGPRINCIPLEOFTACALIBRATOR

TheerrorofTAincludesratioerrorandphaseerror.ThemeasuringoftheerrorofTAorthecalibrationoftheaccuracyofTAusuallyappliesdifferentialmeasuringmethod.ThemethodneedsastandardTAexceptthemeasuredTAandaTAcalibrator.ThereisthesameturnratiobetweenthestandardandmeasuredT4andthestandardTA'saccuracyshouldbe2levelshigherthanthemeasuredone.Thecalibratorfunctionliesinformingcomparisoncircuits,measuring,andshowingtheerroratallrange.Thecomparisoncircuit,alsoreferredtothedifferencemeasuringprinciplecircuit,isshowedinFig.1.BymeasuringthevoltageonI,andRd,calculatethecorrespondingcurrent.Thenthecalibratorcanindicatetheerror.

WhenaTAhasthesameturnratiobetweentheprimaryandsecondarywinding,theself-comparisoncircuitcouldbeusedandisshowninFig.2.Inthefigures,TA0andTAXarestandardandTAbeingmeasuredrespectively.NpandNsareprimaryandsecondarywindingturns.ipandio,id,i,areprimarycurrentsecondarystandardcurrent,secondaryerrorcurrent,secondarycurrentofTAbeingmeasuredrespectively.RoandR,R,aresecondarywinding'sresistanceofstandardTA,errorcurrentdetectingresistance,burdenresistanceofTAbeingmeasuredrespectively.ToandK,Tb.T,arevoltagesamplingpointswhichcancalculatethecurrentInthispaper,onlyvoltagebetweenKandT,voltagebetweenTbandT,arebeingmeasuredandtheyrepresentthevoltageonR,andR,respectively.

Ingeneral,theTAcalibrator'sprincipleofthesampleresistanceshouldbe:

1）itcannotaffecttheaccuracyofthecomparisoncircuit.IntheidealconditionR,andRdshouldbe0,butitcannotbesampled.Sotheremustbesampleresistance,inthispaper,R,asshowninFig,isused;

1）themagnitudeofthesampleresistanceshouldmakethesampledstandardcurrent

anderrorcurrentinprorataandshouldnothavetoomuchdifference.Thesampledresistanceissetbyexperiment:

R,isthesecondarystandardcurrentsamplingresistanceandcanbe0.1-0.50,R,istheerrorcurrentsamplingresistanceandcanbe,R,istheburdenresistanceanditdependsontheTAbeingmeasured.E$samplingthevoltageuoandU,onR,andR,respectively,theratioerrorandphaseerrorareshowedontheLEDthroughsomeprocessandcalculations.

AccordingtotheTAerror'sphasediagram,whenioismaximum,thevalueofidistheratioerror;wheniochangesfromnegativetopositiveandequalsto0,thevalueofidisthephaseerror.Forthesameprinciple,therelationshipisequaltothevoltagesignalU,andud.showedinFig.3.aandbisrepresenttheratioerrorandphaseerrorseparately.theTA'srealratioerrorCandphaseerror6canbefoundoutthroughpropercalculation,

WhereU,istheamplitudeofuoTheT.4calibratordoesn'tneedveryhighaccuracy.1%to3%errorforthecalibratorisenough.Becauseofthedifferencemeasuringprinciple,theerroristhereaderrorofcalibrator,thatis,theTA'serror'serrorbeingmeasured.Butthecalibratorneedstohaveasuitableenlargementfactor.Thecalibratormaximumenlargementfactorthroughallchannelsshouldbe1000times.

III.THEPRINCIPLEOFVIRTUALCALIBRATOR

TheVirtualInstrumentconsistsofthreeparts:

theexternalcomparisoncircuit（showedinFig.1orFig.2）,dataacquisitioncard（PCI-6023）installedinthePCandtheVIprogrambyLabVIEWThen,afterthetwochannels'signalU,andudcomeintothePCthroughtheADC,therestoftheworkisdonebythesoftware.InthispaperweusevoltageU,onR,substituteforU,approximatively.Thevirtualcalibrator'sworkflowchartisshownasfollow:

1）Settheessentialinitialvaluesofthevirtualcalibrator;

2）Pressthestartbuttontostarttowork,adjustingthevoltageregulatorandchangingtheprimarycurrent,lettheratiobetweenprimarycurrentandtheratedcurrentchangefrom

10%to120%;

3）TheVIprogramwillgroupthevoltagesignalU,andud,thenusethedigitalfiltertoeliminatetheharmonic:

4）Calculatetheroot-mean-square（RMS）valueoftlxand14,findouttheamplitudeof21;

5）CalculatetheRMSvalveofio（substituteforf,）,i,andtheratiobetweenioandit'sratedcurrentandshowtheresults.

6）FindouttheaandbshowedinFig.3,calculatetheratioerrorandphaseerrorandshowtheresults.

7）SettheLtimesloop,recordandshowtheerrorsacquiredbyeverytime,

8）Showandprintalltheresultsofcalibration.

9）Stop.

ThefrontpanelofthevirtualcalibratorhastheControls,indictorandSwitch.ThefunctionofControlsistosettheinitialvaluebeforeitworks,ThefunctionoftheIndictoristoshowat1kindsofneededvalues,includingdigital,curveanddiagrametc..'Theswitchdecidesthestartandstopofthevirtualcalibrator.

Ofcourse,tochangethemeasuringrange,theoperatorneedstoadjustthevoltageregulatorandchangetheprimarycurrent.Thisoperationisnecessarylikethatofthetraditionalcalibration,buttherecordingfortheerrorinanyrangeisdonebythevirtualcalibration.Thisconfirmstheaccuracyofrecordingandrelievestheoperator'swork.Theuseofvirtualcalibratorismostinteresting.

Thecontrolsofvirtualcalibratorinclude:

1）Settingthetwosampling（analogueinput）channels;

2）Settingthemagnitudeofsamplingresistanceinthecomparisoncircuit;

3）SettingthesecondaryratedcurrentofmeasuredTA;

4）Settingthenumberofsamplingoferrorcurve;

TheIndictorofvirtualcalibratorhas:

1）Showingratioandphaseerror,ratiobetweentheprimarycurrentandtheratedonesindigital;

2）Showingratioandphaseerror,ratiobetweentheprimary）currentandtheratedonesIncurvesanddiagram,wherethecurveincludetheactivesamplingpointsandfunctionfittingcurves;

3）Showingtheerrorfortheratiobetweentheprimarycurrentandtheratedcurrentfrom10%to120°%;

4）Showingthewaveformofstandardanderrorcurrent,digitalvalueofamplitude;

5）Showingofdigita1RMSvaluethestandardanderrorcurrent;

6）ShowingthepoleofTAinthecomparisoncircuit;

Theaboveshowsthatthefunctionofvirtualcalibratorisgreatlyexpendedthatofthetraditionalones.7111skindofcalibratorisnotonlyconvenienttouse,butalsomakestheperformanceofthecalibratormuchbetter.Fromthefunctionthatshowsthewaveform,wecanfindoutiftherearesomeharmonicsinthecurrent,andconfirmtheaccuracyforthecalibrator.

IV.EXPERIMENT

Thevirtualcalibratorismainlycharacterizedbytheflexibilitycomparedwiththetraditionalones.Althoughthefrontpanelhasmanyfunctions,theycanbeeasilyextendedbytheuser.Sothevirtualcalibratorisofimportantvalueforthenon-standardTAcalibration.

Intheexperiment,theprimarycurrentproducebyastep-upcurrenttransformerandits'currentcontrolledbyavoltage