ASTM_D_3755_-_14.pdf

Designation:D375514Standard Test Method forDielectric Breakdown Voltage and Dielectric Strength ofSolid Electrical Insulating Materials Under Direct-VoltageStress1This standard is issued under the fixed designation D3755;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 dielectricbreakdown voltage and dielectric strength of solid electricalinsulating materials under direct-voltage stress.1.2 Since some materials require special treatment,refer-ence shall also be made to ASTM specifications or to the testmethod directly applicable to the material to be tested.See TestMethod D149 for the determination of dielectric strength ofelectrical insulating materials at commercial power frequen-cies.1.3 This test method is similar to IEC Publication 243-2.Allprocedures in this test method are included in IEC 243-2.Differences between this test method and IEC 243-2 are largelyeditorial.1.4 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.Specific precautionstatements are given in Section 7.2.Referenced Documents2.1 ASTM Standards:2D149 Test Method for Dielectric Breakdown Voltage andDielectric Strength of Solid Electrical Insulating Materialsat Commercial Power FrequenciesD176 Test Methods for Solid Filling and Treating Com-pounds Used for Electrical Insulation(Withdrawn 2013)3D877 Test Method for Dielectric Breakdown Voltage ofInsulating Liquids Using Disk ElectrodesD1711 Terminology Relating to Electrical InsulationD2436 Specification for Forced-Convection Laboratory Ov-ens for Electrical Insulation(Withdrawn 1994)3D3487 Specification for Mineral Insulating Oil Used inElectrical Apparatus2.2 ANSI Standard:4ANSI C68.1 Techniques for Dielectric Tests,IEEE StandardNo.4.2.3 IEC Standard:IEC 243-2 Methods of test for electric strength of solidinsulating materialsPart 2:Additional requirements fortests using direct voltage43.Terminology3.1 Definitions:3.1.1 creepage distance,nshortest distance between twoconductive parts(typically metal),measured along the surfaceof the dielectric insulator.3.1.2 dielectric breakdown voltage,nRefer to Terminol-ogy D1711.3.1.3 dielectric strength,nRefer to Terminology D1711.3.1.4 flashover,nRefer to Terminology D1711.4.Summary of Test Method4.1 The specimen,held in a properly designed electrodesystem,is electrically stressed by the application of an increas-ing direct voltage until internal breakdown occurs.The testvoltage is applied at a uniform rate of increase.The directvoltage is obtained from a high-voltage supply of adequatecurrent capacity and regulation,reasonably ripple-free,withfacilities for measuring and controlling the output voltage.5.Significance and Use5.1 This test method is intended for use as a control andacceptance test for direct-voltage applications.It can also be1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved May 15,2014.Published June 2014.Originallyapproved in 1979.Last previous edition approved in 2004 as D3755 97(2004),which was withdrawn in January 2013 and reinstated in June 2014.DOI:10.1520/D3755-14.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 used in the partial evaluation of material for specific end usesand as a means for detecting changes in material due to specificdeteriorating causes.5.2 Experience indicates that the breakdown value obtainedwith direct voltage usually will be approximately 2 to 4 timesthe rms value of the 60-Hz alternating-voltage breakdown.5.3 For a nonhomogeneous test specimen,the distributionof voltage stress within the specimen is determined by imped-ance(largely capacitive)with alternating voltage.With anincreasing direct voltage,the voltage distribution will still belargely capacitive,although this depends partly on the rate ofvoltage increase.After steady application of direct voltage thevoltage division across the test specimen is determined byresistance.The choice of direct