ASTM_D_3300_-_20.pdf

Designation:D330020Standard Test Method forDielectric Breakdown Voltage of Insulating Liquids UnderImpulse Conditions1This standard is issued under the fixed designation D3300;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 of insulating liquids in a highlydivergent field under impulse conditions and has been foundapplicable to liquids of petroleum origin,natural and syntheticesters.1.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D923 Practices for Sampling Electrical Insulating LiquidsD2864 Terminology Relating to Electrical Insulating Liq-uids and Gases2.2 IEEE Documents:IEEE Standard 4-1995 Techniques for High-Voltage Test-ing33.Significance and Use3.1 This test method is most commonly performed using anegative polarity needle or a sharp defined point to an opposinggrounded sphere(NPS).The NPS breakdown voltage of freshunused liquids measured in the highly divergent field in thisconfiguration depends on the insulating liquid composition,decreasing with increasing concentration of aromatic,particu-larly polyaromatic,hydrocarbon molecules in liquids of petro-leum origin and decreasing with ester molecular structure,either natural or synthetic.3.2 This test method may be used to evaluate the continuityof composition of an insulating liquid from shipment toshipment.The NPS impulse breakdown voltage of an insulat-ing liquid can also be substantially lowered by contact withmaterials of construction,by service aging,particulate matter,and by other impurities.Test results lower than those expectedfor a given fresh liquid may also indicate use or contamination.3.3 Although polarity of the voltage wave has little or noeffect on the breakdown strength of an insulating liquid inuniform fields,polarity does have a marked effect on thebreakdown voltage in nonuniform electric fields.3.4 Transient voltages may also vary over a wide range inboth the time to reach crest value and the time to decay to halfcrest or to zero magnitude.The IEEE standard lightningimpulse test(see 2.2)specifies a 1.2 by 50-s negative polaritywave.4.Apparatus4.1 Impulse Generator,capable of producing a standard 1.2by 50-s full wave adjustable to positive or negative polarity.The generator shall have a nominal voltage rating of at least300 kV adjustable in 10-kV steps.Generators having acapability of 1000 Ws(1000 J)at 300 kV have been foundsatisfactory.4.2 Voltage-Control EquipmentThe controls shall includea suitable measuring device for predetermining the crestvoltage to within 65%.A voltage stabilizer is desirable at theinput to the d-c power supply used for charging the impulse-generator capacitors.4.3 Electrodes:1This 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 Nov.1,2020.Published November 2020.Originallyapproved in 1974.Last previous edition approved in 2012 as D3300 12.DOI:10.1520/D3300-20.2For 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 Electronics Engineers,445 HoesLane,Piscataway,NJ 08855-1331.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.14.3.1 The electrodes shall consist of a polished steel or brasssphere of 0.5 in.(12.7 mm)diameter and a steel