Voltage Transformers and High Voltage Capacitors

1 Page 1 U.S.DepartmentofCommerce NationalBureauofStandards NBSMEASUREMENTSERVICES SpecialPublication250-33 ACalibrationServicefor VoltageTransformersand Higli-VoitageCapacitors Open at page → 2 Page 2 INTRODUONGTHECENTERFORELECTRONICSANDELECTRICALENGINEERING TheCenterforElectronicsandElectricalEngineering(CEEE)istheconfiponentofthe NationalBureauofStandardschargedwithprovidingBureauactivitiesandservices supportingelec... Open at page → 3 Page 3 NBSMEASUREMENTSERVICES: ACalibrationServicefor VoltageTransformersand High-VoltageCapacitors WilliamE.Anderson Electrosystems Division CenterforElectronicsandElectricalEngineering NationalEngineeringLalx)ratory NationalB... Open at page → 4 Page 4 LibraryofCongressCatalogCardNumber:88-600542 NationalBureauofStandardsSpecialPublication250-33 Natl.Bur.Stand.(U.S.),Spec.Publ.250-33,37pages(June1988) CODEN:XNBSAV U.S.GOVERNMENTPRINTINGOFFICE WASHINGTON: 1988 Forsaleby... Open at page → 5 Page 5 —PREFACE ( 'alihrationsandrelatedmeasurementservicesoftheNationalBureauofStandards(NBS)provide themeansforindustry,governmentagencies,ax:aLdemia,andotherstorelatethemeasurements theymaketonationalstandardsand,byextension... Open at page → 7 Page 7 TableofContents 1INTRODUCTION 1 2RANGEOFSERVICES 3 2.1VoltageTransformers 3 2.2Capacitors 4 3MEASUREMENTMETHODOLOGY 5 3.1BasicMeasurementCircuits 5 3.2Capacitors 6 3.3VoltageTransformers 8 4MEASUREMENTINSTRUMENTATION 14... Open at page → 8 Page 8 ListofFigures 1 Scheringbridge 2 2 Basicmeasurement circuitforthecalibrationofahigh-voltagecapacitor 5 3 Basicmeasurement circuitforthecalibrationofavoltagetransformer 6 4 Basicmeasurement circuitforthe4-terminalcalibrat... Open at page → 9 Page 9 ListofTables 1 MeasurementCapability 3 2 GasDensityDependence 8 3ANSIStandardBurdens 12 4 CheckStandardHistory 18 5 DissipationFactorCheckStandard 22 6 ContributionstoUncertainty 23 7 TotalEstimatedUncertainties 23 vii Open at page → 10 Page 10 r Open at page → 11 Page 11 ACalibrationServiceforVoltageTransformers andHigh-VoltageCapacitors WilliamE.Anderson Abstract TheNationalBureauofStandardscalibrationserviceforvoltagetransformersandhigh-voltage capacitors isdescribed.Theserviceforvolta... Open at page → 12 Page 12 Figure1.Scheringbridge. InthepastNBShaduseda"comparative nullmethod"tocalibratevoltagetrajisformers.The unknowntransformerwascomparedtoanNBSreferencetransformerusingavoltagecomparator consistingofavariableresistivedivide... Open at page → 13 Page 13 ThemainlimitationoftheScheringbridgeisaresultofthefactthatthelowsideoftheunknown andstandardcapax;itorsarenotatgroundpotentialatbridgebalance.Therefore,withoutcare- fulguardingofthebridgecomponents,straycurrentscanaffect... Open at page → 14 Page 14 ofsufficientqualitytobeconsideredtransferstandards.Historicallythesetransformershaveshown excellentlong-termstabilityrarelychangingbymorethan100ppminratioorO.lmradinphase (atorbelowratedburden)forperiodsaslongasthirtyyea... Open at page → 15 Page 15 V Cx Nd Cs Nx^-n=r^ Ns Figure2.B«isicmeasurement circuitforthecalibrationofahigh-voltagecapacitor. 3MEASUREMENTMETHODOLOGY 3.1BasicMeasurementCircuits Thecurrentcomparatorbridgeusedtocalibratevoltagetransformersandhigh-v... Open at page → 16 Page 16 Vp Figure3.Basicmeasurement circuitforthecalibrationofavoltagetransformer. 3.2Capacitors GeneralMeasurementTechnique Capacitorsaremeasuredbybalancingthecurrentthroughthecapax:itorundertestagainstthe currentthroughastanda... Open at page → 17 Page 17 V Nx -±: Ns Figure4.Basicmeasurement circuitforthe4-terminalcalibrationoflargecapacitors. shouldbeatleast10microamperes.Thecurrentthroughthecustomer'scapacitorcanrangefrom 10microamperesto1000amperes. VoltageDependence F... Open at page → 18 Page 18 Table2.GasDensityDependence GAS dC/dPatT=22.8°C (unitsofpicofarads/pascal) SFe CO2 He (2.012±0.022)X10-^+[(5.1±0.6)xlO'^^jP (0.903±0.015)X10-«+[(1.4±0.4)xlO'^^jp (0.075±0.004)X10-6+[(0.2±0.1)xlO'^^jp surementprocess.Thea... Open at page → 19 Page 19 e BURDEN DVM r~ CURRENT I COMPARATOR [ BRIDGE I — 1 ::=FCp L_ _l Figure5.Basicmeasurement circuitforthecalibrationofavoltagetransformerwithadigital voltmeter(DVM)andsecondaryburden. hasanestimateduncertaintyoflessthan±0.... Open at page → 20 Page 20 e 1 BURDEN DVM Cs CURRENT -\COMPARATOR r I BRIDGE I I Cp Figure6.Measurementcircuitforthecalibrationofavoltagetransformer.Connectionoflow-voltage capacitorasshownisincorrect. BURDEN DVM ICURRENT I ]COMPARATOR p I BRIDGE... Open at page → 21 Page 21 e BURDEN DVM ICURRENT !COMPARATOR I BRIDGE _l Figure8.Measurement circuitforthecalibrationofavoltagetransformer.Measurementgroundis defined.Transformerexcitationcurrentflowsfromthemeasurementgroundtobuildingground. three... Open at page → 22 Page 22 Table3.ANSIStandardBurdens ANSIBurden Volt-cimperes PowerFax:tor(Lagging) W 12.5 0.10 X 25 0.70 M 35 0.20 Y 7 0.85 Z 200 0.85 TL 400 0.85 Thevoltagetransformer willberepresentedasanidealtransformerwithsomeunknownseries o... Open at page → 23 Page 23 Figure10.Equivalentcircuitofavoltagetransformerwithsecondaryburden Figure11.Capacitiveburdenbox. ThepowerfactorofburdenCiscos^c?RCFcistheratiocorrectionfactorcalculatedforburdenC, andFcistheanglebywhichthesecondaryvoltag... Open at page → 24 Page 24 predictivecapabilitiesofeqs(7)and(8)forthetransformerundertest.Ifaproblemisdiscovered, theerrorbudgetisadjustedaccordingly. Theabovediscussionmightenablecustomersofthevoltagetransformercalibrationservicetobetter designth... Open at page → 25 Page 25 V \/lx Nd \^Is Figure12.Basiccurrentcomparatorbridge. Thecurrentcomparatorbridgecanbethoughtofasavoltagecomparatortransformerarmbridge inwhichthedetectorandpowersourcehavebeeninterchanged. Traditionally,thedisadvantageof... Open at page → 26 Page 26 V Cx D Nd Nx ,_rrvr\ ^ Ns Cs Is Figure13.Currentcomparatorbridgewithhigh-voltageresistorforin-phasecurrentbalance. V Figure14.Currentcomparatorwithsuperiorin-phasecurrentbalance. 16 Open at page → 27 Page 27 appliedtoanidenticalstandardresistorasshowninfigure14sothatthecurrentfromthestandard winding,N,,reachingtheoperationalamplifierhcisnophasedefect.Thein-phasecurrentintothe standardwinding,N,,isthenequalto: /R. (11) Sincet... Open at page → 28 Page 28 V Figure15.Currentcomparatorbridgemodifiedfor4-terminalcapacitancemeasurements. Table4.CheckStandardHistory DateCapacitanceRatio Date CapacitanceRatio 6/80 1.000025 1/84 1.000032 6/81 1.000028 5/84 1.000033 9/81 1.000027... Open at page → 29 Page 29 V Cx -1>H(- Cs' D Nd LAAAJ Nx Figure16.Currentcomparatorbridgewithexternalrangeextender. 19 Open at page → 30 Page 30 V a Cx Cs ICURRENT I iCOMPARATOR h I BRIDGE j -JLT Figure17.Circuitforcheckingoperationofdissipationfactormeasurementofcurrentcomparator bridge. provethatthebridgeisstillworkingtotheppmlevel,itcanalerttheuserofchangeslar... Open at page → 31 Page 31 V (X Cx Cs 1^CURRENT ^ HCOMPARATOR V I BRIDGE I -JLT Figure18.Circuitforcheckingoperationofdissipationfactormeasurementofcurrentcomparator bridge.Inputisgroundedinordertomeasureeineq(18). Sincee^Vsubtractingeq(19)fromeq(... Open at page → 32 Page 32 Table5.DissipationFactorCheckStandard Measured Correction Corrected Theoretical Date a (DF) (DFo) {DFm) {a/2nfRC^) 7/82 0.0003 0.08003 0.0002 0.07983 0.07977 0.003 0.7982 0.0002 0.7980 0.7977 -0.003 -0.7979 0.0002 -0.798... Open at page → 33 Page 33 Table6.Contributions toUncertainty Uncertainties Random Systematic Bridgemeasurement ±2(±2)±75(±25) Secondaryvoltagesetting ±50(±10) Burdensetting ±50(±10) Transformerself-heating ±75(±20) Capacitanceratiomeasurement ±2(... Open at page → 34 Page 34 ±10ppmforcapacitance(±1x10~^ fordissipationfactor).Therandomerrorassociatedwiththe capax:itancemeasurement is±lppmand±1xlO"^fordissipationfactor.Conservatively then, NBScouldcalibrateacustomer'scapacitortoanoveralluncert... Open at page → 35 Page 35 U.S.DEPARTMENTOFCOMMERCE NATIONALBUREAUOFSTANDARDS GAITHERSBURG,MD20899 REPORTOFCALIBRATION VOLTAGETRANSFORMER 120-14,400to120Volts,60Hertz,4.4Volt-Amperes XXXXX,SerialNo.??????? Submittedby CustomerName CustomerAddress... Open at page → 36 Page 36 U.S.DEPARTMENTOFCOMMERCE NATIONALBUREAUOFSTANDARDS GAITHERSBURG,MD20899 REPORTOFCALIBRATION STANDARDCAPACITOR XXXXX,SerialNo.??????? Submittedby CustomerName CustomerAddress CapacitanceanddissipationfactorweremeasuredonF... Open at page → 37 Page 37 APPENDIX Thevoltagetransformer willberepresented asanidealtransformerwithsomeunknownseries outputimpedance,Zq,asshowninfigure9.Themodelhasbeenshowntobesufficientlyaccurate experimentally.Therelationshipbetweentheinputvol... Open at page → 38 Page 38 Bothexponentialshaveargumentsmuchlessthanonesothatdiscardingquadraticandhigherorder termsandequatingtheimaginarycomponentsoftheleftandrightsidesofeq(30)oneobtains Ei Ei Eo orfromeq(25)assumingZg<CZc To XqRc—XcRq Theresis... Open at page → 39 Page 39 or and Xo« (^^) [(ro-r^cos^,+(RCF,-RCF,)sin^,]. (44) Usingeqs (37),(43),and(44)andtherelations: cos6ccos 6t+sin6csin 6t—cos{dt—6c) (45) cos^csin^t—sin0ccos=sin(0t— 6c) (46) onefinds RCFc«RCF,+(^g^^jr) [(RCF,-RCF^)cos(0^-... Open at page → 40 Page 40 REFERENCES [1]F.K.Harris,ElectricalMeasurements,JohnWiley&Sons,NewYork,pp.576-577(1966). [2]F.K.Harris,ElectricalMeasurements,JohnWiley&Sons,NewYork,pp.687-738(1966). [3]N.L.KustersandO.Petersons,"ATransformer-Ratio-Arm... Open at page → 41 Page 41 NBS-n4A(REV.2-gC) U.S.DEPT.OFCOMM. 1.PUBLICATIONOR 2.PerformingOrgan.ReportNo.3.PublIcationDate BIBLIOGRAPHICDATA REPORTNO. SHEET(Seeinstructions) NBS/SP-250/33 June1988 4.TITLEANDSUBTITLE ACalibrationServiceforVoltageTr... Open at page → 43 Page 43 THESP250SERIESONNBSMEASUREMENTSERVICES* SP250-1 SP250-2 SP250-3 SP250^ SP250-5 SP250-6 SP250-7 SP250-8 SP250-9 SpectralRadianceCalibrations SN003-003-02792-8 $3.50 FarUitravioietDetectorStandards SN003-003-02810-0 $4.25... Open at page → 44 Page 44 U.S.DepartmentofCommerce NationalBureauofStandards Gaithersburg,MD20899 OfficialBusiness PenaltyforPrivateUse$300 stimulatingAmericjsProgress 1913-1988 Open at page →