ASTM_D_2477_-_07_2012.pdf

Designation:D247707(Reapproved 2012)Standard Test Method forDielectric Breakdown Voltage and Dielectric Strength ofInsulating Gases at Commercial Power Frequencies1This standard is issued under the fixed designation D2477;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the dielec-tric breakdown voltage and dielectric strength of insulatinggases used in transformers,circuit breakers,cables,and similarapparatus as an insulating medium.The test method is appli-cable only to gases with boiling points below room temperatureat atmospheric pressure.1.2 This standard may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.1.3 Mercury has been designated by EPA and many stateagencies as a hazardous material that can cause centralnervous system,kidney and liver damage.Mercury,or itsvapor,may be hazardous to health and corrosive to materials.Caution should be taken when handling mercury and mercurycontaining products.See the applicable product MaterialSafety Data Sheet(MSDS)for details and EPAs website http:/www.epa.gov/mercury/faq.htm for additional informa-tion.Users should be aware that selling mercury and/ormercury containing products into your state may be prohibitedby state law.2.Referenced Documents2.1 ASTM Standards:2D2864 Terminology Relating to Electrical Insulating Liq-uids and Gases2.2 IEEE Standard:3No.4 Standard Techniques for High Voltage Testing2.3 ASTM Adjuncts:Dielectric cell assembly and detail(2 drawings)43.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method,referto Terminology D2864.4.Significance and Use4.1 The dielectric breakdown voltage and dielectric strengthof an insulating gas in a uniform field depends primarily on themolecular structure of the gas.As different gases are mixedeither by plan or by contamination,any change in dielectricbreakdown voltage and dielectric strength will depend on boththe nature and proportion of the individual gases.This testmethod uses plane and spherical electrodes which provide anearly uniform field(see Appendix)in the area of electricaldischarge.It is suitable for determining the dielectric break-down voltage and dielectric strength of different gases andmixtures thereof for research and application evaluations andalso as a field test.A more complete discussion of thesignificance of the dielectric strength test is given in theAppendix.5.Apparatus5.1 Electrical Apparatus:5.1.1 Transformer The desired test voltage may be mostreadily obtained by a step-up transformer energized from avariable low-voltage commercial power frequency source.Thetransformer and controlling element shall be of such size anddesign that,with the test specimen in the circuit,the crest factor(ratio of maximum to mean effective)of the 60-Hz test voltagedoes not differ by more than 65%from that of a sinusoidalwave over the upper half of the range of test voltage.The crestfactor may be checked by means of an oscilloscope,a spheregap,or a peak-reading voltmeter in conjunction with an rmsvoltmeter.Where the waveform cannot be determinedconveniently,a transformer having a rating of not less than121This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D27.05 on Electrical Test.Current edition approved May 1,2012.Published May 2012.Originallyapproved in 1966.Last previous edition approved in 2007 as D2477 07.DOI:10.1520/D2477-07R12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from The Institute of Electrical and Electronic Engineers,Inc.(IEEE),445 Hoes Ln.,P.O.Box 1331,Piscataway,NJ 08854-1331.4Detailed drawings of this apparatus are available at a nominal cost from:ASTMInternational Headquarters.Order Adjunct No.ADJD2477.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 kVA at the usual breakdown voltage shall be used.Transform-ers of larger kVA capacity may be used,but in no case shouldthe power frequency short circuit current in the specimencircuit be outside the range of 1 to 10 mA/kV of appliedvoltage.This limitation of current may be accomplished byusing a suitable external series resistor or by employing atransformer with sufficient inhe