1、Designation:D25714(Reapproved 2021)1Standard Test Methods forDC Resistance or Conductance of Insulating Materials1This standard is issued under the fixed designation D257;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of la
2、st revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1NOTEEditorial changes were made to 4.1(grammar cor
3、rection)and Table 1(“p”changed to“”)in March 2021.1.Scope1.1 These test methods cover direct-current procedures forthe measurement of dc insulation resistance,volume resistance,and surface resistance.From such measurements and thegeometric dimensions of specimen and electrodes,both vol-ume and surfa
4、ce resistivity of electrical insulating materialscan be calculated,as well as the corresponding conductancesand conductivities.1.2 These test methods are not suitable for use in measuringthe electrical resistance/conductance of moderately conductivematerials.Use Test Method D4496 to evaluate such ma
5、terials.1.3 These test methods describe several general alternativemethodologies for measuring resistance(or conductance).Specific materials can be tested most appropriately by usingstandardASTM test methods applicable to the specific materialthat define both voltage stress limits and finite electri
6、ficationtimes as well as specimen configuration and electrode geom-etry.These individual specific test methodologies would bebetter able to define the precision and bias for the determina-tion.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It i
7、s 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.1.5 This international standard was developed in accor-dance with internationally recognized principles on stan
8、dard-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:2D150 Test Methods for AC Loss Characteristics and
9、 Permit-tivity(Dielectric Constant)of Solid Electrical InsulationD374/D374M Test Methods for Thickness of Solid Electri-cal InsulationD1169 Test Method for Specific Resistance(Resistivity)ofElectrical Insulating LiquidsD1711 Terminology Relating to Electrical InsulationD4496 Test Method for D-C Resi
10、stance or Conductance ofModerately Conductive MaterialsD5032 Practice for Maintaining Constant Relative Humidityby Means of Aqueous Glycerin SolutionsD6054 Practice for Conditioning Electrical Insulating Mate-rials for Testing(Withdrawn 2012)3E104 Practice for Maintaining Constant Relative Humidityb
11、y Means of Aqueous Solutions3.Terminology3.1 Definitions:3.1.1 The following definitions are taken from TerminologyD1711 and apply to the terms used in the text of these testmethods.3.1.2 conductance,insulation,nthe ratio of the totalvolume and surface current between two electrodes(on or in aspecim
12、en)to the dc voltage applied to the two electrodes.3.1.2.1 DiscussionInsulation conductance is the recipro-cal of insulation resistance.3.1.3 conductance,surface,nthe ratio of the currentbetween two electrodes(on the surface of a specimen)to the dcvoltage applied to the electrodes.3.1.3.1 Discussion
13、(Some volume conductance is unavoid-ably included in the actual measurement.)Surface conductanceis the reciprocal of surface resistance.1These test methods are under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommitt
14、ee D09.12 on Electrical Tests.Current edition approved March 1,2021.Published May 2021.Originallyapproved in 1925.Last previous edition approved in 2014 as D257 14.DOI:10.1520/D0257-14R21E01.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at service
15、astm.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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2
16、959.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.13.1.4 conductance,volume,nthe ratio of the current in thevolume of a specimen between two electrodes(on or in thespecimen)to the dc voltage applied to the two electrode
