Presentation on theme: "Comparison of Standards – ANSI / IEEE and IEC Prepared by the Task Force under the Standards Subcommittee IEEE Transformers Committee March 2011 "— Presentation transcript:
1Comparison of Standards – ANSI / IEEE and IEC Prepared by the Task Force under the Standards Subcommittee IEEE Transformers Committee March 2011 TF Chair: H. Jin Sim TF Members: Vinay Mehrotra Ajith Varghese Hali Moleski Richard Marek Bill Henning Hasse Nordman Jim Thompson
2TF Report SummaryThe comparisons are based on the latest published standards unless identified otherwiseIt is the directive of the Standards Subcommittee to publish this comparison study each time a major standard (IEEE C , C , or IEC ) is approved and publishedThe purpose of this study is to provide list of major differences between IEEE and IEC standards to the members of the group working on these documentsIn addition to these major documents, we will include comparisons of other standards and guides commonly used for Power TransformersIt is hoped that the readers would consider harmonizing the standards as best as they can as they develop these standards for the industry.
3Included in March 2011 Report are; C with IEC (2000)By Vinay Mehrotra / Waukesha Electric SystemsTransformer Testing C section 8 & 9 and C with IEC (2000) and IEC (2000)By Ajith Varghese / Waukesha Electric SystemsDGA during Factory (Temperature Rise) Tests of Mineral Oil Immersed Electrical EquipmentBy Hali Moleski / SD Myers Inc.High Temperature Liquid-Immersed TransformersR. P. Marek / DuPont Energy SolutionsC Vs. IEC ComparisonBill Henning / Waukesha Electric SystemsTemperature RiseH Nordman / ABB TransformersIEC and IEC Comparison to IEEE CJim Thompson / T&R Service CompanyExamples of differences followComplete file
4Impulse Testing IEEE IEC Lightning Sequence Line : RFW, CW , CW , FW Neutral : RFW, FW , FW( for 200 BIL)Line : RFW , FW , FW , FWDirectly Earthed Neutral : Not Recommended.Not directly earthed : Impulse verified by either direct method and indirect method.Impulse TapMinimum effective turns in the winding under test.Tapping range is +/- 5 % or less : Principal Tap .Tapping range is larger than +/- 5 %: Principal Tap & two extremesChopping Time> 110 BIL - Min 3 us ;110 BIL - Min 2 us; 95 BIL : Min 1.8us ; < 95 BIL : 1.5 usBetween 2 and 6 microsecondSwitching SequenceRSS, SS , SSRSS , SS , SS, SSSS Wave shapeTime to Crest – 100us ; 90 % - 200us; Time to first Zero – 1000 us .. All MinTime to Crest – 100us ; 90 % - 200us; Time to first Zero – 500 us ( Min – preferably 1000 us )
5Induce Test IEEE IEC IEEE Class I / IEC ACSD Duration : 7200 cycle ; Max Test time : 60 secNo PD MeasurementDuration : 120 X ( Rated Freq / Test frequency )Min test time : 15 secTheoretical Max test time : 120 secIEEE Class II / IEC >72.5 KVUm followed by 1 UmPD Acceptance limit : hr< 170 KV ACSD : AC Test Volts followed by 1.3 Um for 5 minPD Acceptance limit : UmPD Acceptance limit : Um> 170 KV ACLD : 1.7 Um followed by 1.5 Um for 60 min or 30 min (< 300 KV )PD Acceptance 1.5Um :500 pCPD Acceptance 1.1 Um :100 pCNon Uniform Insulated windingsNot definedTwo tests required :Phase to EarthPhase to phase
6Acceptance criteria Cont’d IEEE IEC Ratio and polarity Within +/-0.5 % of Name plate .For all for Volts per turn exceed 0.5 % of NP voltage , turn ratio of winding shall be the nearest turnRated tap :Lower of+/- 0.5 % of declared ratio+/- 1/10th of actual impedance of Rated tapOther Tap : agreement between supplier and buyer but not lower than a and bImpedanceTwo wdg withZ > 2.5 % = +/- 7.5 %Z < 2.5 % = +/- 10 %Three wdg / Zig Zag , AutoTwo wdg / first pair of multi wdg ( Principal Tap )Z > 10 % = +/- 7.5 %Z < 10 % = +/- 10 % Two wdg /first pair of multi wdg ( other Tap )Z > 10 % = +/- 10 %Z < 10 % = +/- 15 %Auto / second pair of multi wdg ( Principal Tap ) = +/- 10 %Auto / second pair of multi wdg ( other Taps ) = +/- 15 %Cont’d
7Acceptance criteria ( cont’d) IEEEIECLossesNo load – not to exceed 10 % of specifiedLoad loss – not to exceed 6 %Not a criteria for rejectionTotal losses : + 10 % with individual components less than + 15%No load currentNot specified+30 % of declared values
8No load test IEEE IEC Waveform correction PC (Tm) = Pm /(P1+kP2 ) K = (RMS volt / Average Volt )2P1:P2 = 0.5P0 = Pm (1+d )d= ( RMS volts – Average Volt ) /RMS voltsMaximum Waveform correctionMax magnitude of correction : 5 %Max difference in Voltmeter reading shall be below 3 %Ambient for No Load testAverage oil within +/- 10 deg of reference temp ( 20 0C ). Difference between top and Bottom oil temp does not exceed 5 0CEmpirical formula is provided for correction outside the rangeApproximately at factory ambient tempNo Temperature correctionMeasurement of harmonicsNo RequirementsRequired to be measured as percentage of fundamental components – No limitsFrequency for testingTest source frequency shall be under +/- 0.5 % of rated frequency.Rated frequency – No tolerance specified.Excitation currentExpressed in per unit or % of rated line current ( lowest rating )Expressed in Amps or per unit or % of rated winding current ( largest rating )
9Load test IEEE IEC Min Load current 50 % of rated current Ambient conditions for testTop and Btm Oil difference not to exceed 50 c.Frequency of test source within +/- 0.5 % of nominalTop and Btm Oil difference shall be smallImpedance on Other TapsExtreme tap measurement required on first unit.If tapping range exceed +/- 5 % , impedances on two extreme taps are also requiredZero Sequence Test -Unit of measureReported in % of KVA baseExpressed in ohms per phaseTest procedure for windings with two neutralMinimum of three tests are specified to arrive Z1 , Z2 , Z3Testing based on agreement between manufacturer and purchaser.Resistance MeasurementTest environmentMeasure cold resistance after 3- 8 hours with no excitation and current in winding.Top & BTM difference shall not exceed 5 degreeMeasure cold resistance after 3 hour minimum with no excitation
10Sound Test IEEE IEC Method Sound Pressure levels – A weighted, octave , discrete frequencyBoth Sound Pressure and Sound Intensity are Valid and is to be agreed between manufacturer and purchaserLoad conditionNo LoadNo Load or Load - To be agreed between manufacturer and purchaserTest TapPrincipal unless agreed differentlyMeasurement contour0.3 m from sound producing surface ;2 m for fansBelow 2.4 m and below - at half height, at 1/3 and 2/3 for higher height units. Microphone 2 meter apart ; min 4Below 2.5 m and below - at half height, at 1/3 and 2/3 for higher heights.Microphone 2 meter apart ; min 6Rated / Reduced Current TestNo methodology providedLog addition of NL and Load sound to arrive at sound during operation .Not Required if “ ( log MVA ) ” is 8 dB lower than guarantee
11Sound Test IEEE IEC Sound Intensity Measurement Not defined Procedure outlinedSound Power levelNot definedFormula is provide to estimate Sound Power level based on pressure or intensity measurementAmbient sound correctionAllows 0 to -1.6db correction for ambient to transformer sound difference of 10 to 5 dbIf the difference is between 3db and 8 db , correction is applied based on formula involving ambient to tested sound level and environmental correction factor k which depend of sound reflection from surfaces.. Max allowable K is 7 db.
12Miscellaneous Tests IEEE IEC Tap changer No defined Test procedure or criteriaDe-energized 8 cycles ; de-energized and 85 % Aux Voltage 1 cycle ; energized 1 cycle ; rated current 10 operations across reversing/coarse-fine tapEMCNot definedTransformer is considered as passive but accessories may be . But no guideline of handling or test required is providedInsulation Power factor TestDetailed procedure and acceptance PF < 0.5 %Not defined in IECInsulation Resistance TestDetailed procedure but no limitsControl wiring1.5 KV AC 60 Hz2 KV for 1 minute