ASTM_D_3638_-_12.pdf

Designation:D363812Standard Test Method forComparative Tracking Index of Electrical InsulatingMaterials1This standard is issued under the fixed designation D3638;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.Scope*1.1 This test method evaluates in a short period of time thelow-voltage(up to 600 V)track resistance or comparativetracking index(CTI)of materials in the presence of aqueouscontaminants.1.2 The values stated in metric(SI)units are to be regardedas standard.The inch-pound equivalents of the metric units areapproximate.1.3 This standard is technically equivalent to the version ofIEC Publication 112 cited in 2.2.However,the 2007 version ofIEC 60112 Fourth Edition yields numerical CTI values that arevery likely to differ significantly from this standard.1.4 This standard does not purport to address all of thesafety problems,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:2D1711 Terminology Relating to Electrical InsulationD6054 Practice for Conditioning Electrical Insulating Mate-rials for Testing(Withdrawn 2012)32.2 IEC Publication:112 Recommended Method for Determining the Compara-tive Track Index of Solid Insulating Materials UnderMoist Conditions,1971 Second Edition460112 Recommended Method for Determining the Com-parative Track Index of Solid Insulating Materials UnderMoist Conditions,2007 Fourth Edition43.Terminology3.1 Definitions:3.1.1 tracka partially conducting path of localized dete-rioration on the surface of an insulating material.3.1.2 trackingthe process that produces tracks as a resultof the action of electric discharges on or close to an insulationsurface.3.1.3 tracking,contaminationtracking caused by scintilla-tions that result from the increased surface conduction due tocontamination.3.1.4 tracking resistancethe quantitative expression of thevoltage and the time required to develop a track under thespecified conditions.3.1.5 For other terminology,refer to Terminology D1711.3.2 Definitions of Terms Specific to This Standard:3.2.1 comparative tracking indexan index for electricalinsulating materials which is arbitrarily defined as the numeri-cal value of that voltage which will cause failure by trackingwhen the number of drops of contaminant required to causefailure is equal to 50.3.2.1.1 DiscussionThe voltage value is obtained from aplot of the number of drops required to cause failure bytracking versus the applied voltage.3.2.2 failure,nan attribute of an electrical circuit contain-ing an electrical-current-sensing device that rapidly decreasesthe applied voltage to zero if the current in the circuit exceedsa predetermined limit.4.Summary of Test Method4.1 The surface of a specimen of electrical insulatingmaterial is subjected to a low-voltage alternating stress com-bined with a low current which results from an aqueouscontaminant(electrolyte)which is dropped between two op-posing electrodes every 30 s.The voltage applied across theseelectrodes is maintained until the current between them ex-ceeds a predetermined value.This condition constitutes afailure.Additional specimens are tested at other voltages sothat a relationship between applied voltage and number ofdrops to failure can be established through graphical means.1This 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 Jan.1,2012.Published February 2012.Originallyapproved in 1977.Last previous edition approved in 2007 as D3638 07.DOI:10.1520/D3638-12.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from the International Electrotechnical Commission,Geneva,Swit-zerland.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 The numerical value of the voltage which causes failure withthe application of 50 drops of the electrolyte is arbitrarilycalled the comparative tracking index.This index provides anindication of the relative track resistance of the material.5.Significance and Use5.1 Electrical equipment can fail as a result of electricaltracking of insulating material that is exposed to variouscontaminating environments and surface co