ASTM_D_495_-_14.pdf

Designation:D49514Standard Test Method forHigh-Voltage,Low-Current,Dry Arc Resistance of SolidElectrical Insulation1This standard is issued under the fixed designation D495;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method covers,in a preliminary fashion,thedifferentiation of similar materialsresistance to the action of ahigh-voltage,low-current arc close to the surface of insulation,when a conducting path is formed causing the material tobecome conducting due to the localized thermal and chemicaldecomposition and erosion.1.2 The usefulness of this test method is very severelylimited by many restrictions and qualifications,some of whichare described in the following paragraphs and in Section 5.Generally,this test method shall not be used in materialspecifications.Whenever possible,alternative test methodsshall be used,and their development is encouraged.1.3 This test method will not,in general,permit conclusionsto be drawn concerning the relative arc resistance rankings ofmaterials that are potentially subjected to other types of arcs:for example,high voltage at high currents,and low voltage atlow or high currents(promoted by surges or by conductingcontaminants).1.4 The test method is intended,because of its convenienceand the short time required for testing,for preliminary screen-ing of material,for detecting the effects of changes informulation,and for quality control testing after correlation hasbeen established with other types of simulated service arc testsand field experience.Because this test method is usuallyconducted under clean and dry laboratory conditions rarelyencountered in practice,it is possible that the prediction of amaterials relative performance in typical applications and invarying“clean to dirty”environments will be substantiallyaltered(Note 1).Caution is urged against drawing strongconclusions without corroborating support of simulated servicetests and field testing.Rather,this test method is useful forpreliminary evaluation of changes in structure and compositionwithoutthecomplicatinginfluenceofenvironmentalconditions,especially dirt and moisture.NOTE1By changing some of the circuit conditions described hereinit has been found possible to rearrange markedly the order of arcresistance of a group of organic insulating materials consisting ofvulcanized fiber and of molded phenolic and amino plastics,somecontaining organic,and some inorganic,filler.1.5 While this test method uses dry,uncontaminated speci-men surfaces,Test Method D2132,Test Methods D2303,andTest Method D3638 employ wet,contaminated specimensurfaces.Their use is recommended for engineering purposesand to assist in establishing some degree of significance to thistest method for quality control purposes.21.6 This test method is not applicable to materials that donot produce conductive paths under the action of an electricarc,or that melt or form fluid residues that float conductiveresidues out of the active test area thereby preventing forma-tion of a conductive path.1.7 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.1.8 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.For specificprecautionary statements,see 6.1.14,6.1.19,Section 7,and10.1.1.2.Referenced Documents2.1 ASTM Standards:3D1711 Terminology Relating to Electrical Insulation1This 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 April 1,2014.Published May 2014.Originallyapproved in 1938.Last previous edition approved in 2004 as D495 94(2004),which was withdrawn in January 2013 and reinstated in April 2014.DOI:10.1520/D0495-14.2Also helpful is Test Method D2302 for Wet Tracking Resistance of ElectricalInsulating Materials with Controlled Water-to-Metal Discharges.This test methodwas withdrawn and last appeared in the 1982 Annual Book of ASTM Standards,Part39.3For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-