ASTM_D_3300_-_12.pdf

Designation:D330012Standard Test Method forDielectric Breakdown Voltage of Insulating Oils ofPetroleum Origin Under Impulse 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 oils in a highly divergentfield under impulse conditions.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 and health practices and determine the applica-bility of regulatory limitations prior to use.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 point opposing a grounded sphere(NPS).TheNPS breakdown voltage of fresh unused oils measured in thehighly divergent field in this configuration depends on oilcomposition,decreasing with increasing concentration ofaromatic,particularly polyaromatic,hydrocarbon molecules.3.2 This test method may be used to evaluate the continuityof composition of an oil from shipment to shipment.The NPSimpulse breakdown voltage of an oil can also be substantiallylowered by contact with materials of construction,by serviceaging,and by other impurities.Test results lower than thoseexpected for a given fresh oil may also indicate use orcontamination of that oil.3.3 Although polarity of the voltage wave has little or noeffect on the breakdown strength of an oil in uniform fields,polarity does have a marked effect on the breakdown voltage ofan oil 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:4.3.1 The electrodes shall consist of a polished steel or brasssphere of 0.5 in.(12.7 mm)diameter and a steel point.Thepoint may be an ordinary steel phonograph needle with a 0.06mm 6 20%radius of curvature of point.4Needles with drawntips are not recommended.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 Jan.1,2012.Published January 2012.Originallyapproved in 1974.Last previous edition approved in 2006 as D3300 00(2006).DOI:10.1520/D3300-12.2For 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 08855-1331.4The following steel needle has been found satisfactory for this method:Type LNickel Plated Steel Phonograph Needle.The sole source of supply of the apparatus known to the committee at this timeis Victrola Repair Service,206 Cliff St.,St.Johnsbury,VT,05819.If you are awareof alternative suppliers,please provide this information to ASTM InternationalHeadquarters.Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.3.2 The effect of variation in the radius of curvature ofpoint is subject to further investigation.Both electrodes shallbe easily replaceable.4.4 Test Cell:4.4.1 The test cell shall be made of a material of highdielectric strength and of such dimensions that the electricalbreakdow