1、Designation:D 3151 88(Reapproved 1998)An American National StandardStandard Test Method forThermal Failure of Solid Electrical Insulating MaterialsUnder Electric Stress1This standard is issued under the fixed designation D 3151;the number immediately following the designation indicates the year ofor
2、iginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the thermalfailure of
3、solid electrical insulating materials subjected toelectric stress at commercial power frequencies.This testmethod has been developed for testing materials such as certainglasses and ceramics,that exhibit large increases in dielectricloss with increasing temperature.1.2 This standard does not purport
4、 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.A specific hazardstatement is given in 10.1.2.Refere
5、nced Documents2.1 ASTM Standards:D 149 Test Method for Dielectric Breakdown Voltage andDielectric Strength of Solid Electrical Insulating Materialsat Commercial Power Frequencies2D 374 Test Methods for Thickness of Solid Electrical Insu-lation2D 1711 Terminology Relating to Electrical Insulation2E 1
6、45 Specification for Gravity-Convection and Forced-Ventilation Ovens32.2Other Standards:IEEE Standard No.4 Measurements of Voltage in DielectricTests43.Terminology3.1 Definition:3.1.1 dielectric breakdown voltagesee TerminologyD 1711.3.2 Definitions of Terms Specific to This Standard:3.2.1thermal di
7、electric breakdown,nan increase in thedissipation factor or conductance in the test material whichleads to failure by thermal runaway.The time to failure and thevoltage stress at which thermal breakdown occurs is influencedby the ambient test temperature,the test voltage,the dimen-sions of the test
8、specimen,the specific heat of the material,andits thermal conductivity.3.2.2 thermal dielectric breakdown voltage,nthe voltageat which thermal dielectric breakdown takes place at a speci-fied ambient temperature and thermal transfer condition.3.2.3 thermal runaway,na mode of response exhibited bycer
9、tain materials which,when subjected to electric stressexceeding a critical value,undergo a rise in temperature whichitself increases the conductance of the material,further increas-ing the temperature,and so on in a self-escalating manner.4.Significance and Use4.1 This test method is intended to sup
10、plement the standarddielectric strength test procedure(Test Method D 149)for testsat elevated temperatures,particularly of glasses and ceramics.The method determines at elevated temperature the potentialdifference at which the current becomes so great due toincreased conductance that dielectric heat
11、ing causes the tem-perature in the material to rise and ultimately cause thermalelectric breakdown to occur.4.2 This test method is intended for use as a control andacceptance test.It may be used also in the partial evaluation ofmaterials for specific end uses and as a means for detectingchanges in
12、materials due to specific deteriorating causes.Amore complete discussion of the significance of thermaldielectric breakdown tests is given in Annex A1.5.Apparatus5.1 High-Voltage Test EquipmentSuitable equipment isdescribed in Test Method D 149.The transformer rating shouldbe adequate to maintain a
13、sine wave at full-load current.Higherratings than specified in Test Method D 149 are usuallyrequired.5.2 VoltmeterThe voltage shall be measured in accor-dance with IEEE Standard No.4.The response time of thevoltmeter shall be such that its time lag does not introduce an1This test method is under the
14、 jurisdiction of ASTM Committee D-9 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved Aug.26,1988.Published October 1988.Originallypublished as D 315173.Last previous edition D 315179.2Annual Book of A
15、STM Standards,Vol 10.01.3Annual Book of ASTM Standards,Vol 14.02.4Available from the Institute of Electrical and Electronics Engineers,Inc.,345E.47th St.,New York,NY 10017.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.error greater than
16、 1%of full scale at the rate of rise used.Theoverall accuracy of the voltmeter and the voltage-measuringdevice used shall be such that the measurement error will notexceed 5%.5.3 Test Area,containing the test chamber and high-voltagetransformer shall be contained in a suitably grounded metalenclosure with a door provided with an interlock that interruptsthe high voltage when opened.5.4 Test Chamber:5.4.1 The test chamber shall consist of an electrically heatedfurnace and an auxiliary temperature