1、Designation: D 3426 97 (Reapproved 2004)An American National StandardStandard Test Method forDielectric Breakdown Voltage and Dielectric Strength ofSolid Electrical Insulating Materials Using Impulse Waves1This standard is issued under the fixed designation D 3426; the number immediately following t
2、he 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method cover
3、s the determination of dielectricstrength of solid electrical insulating materials undersimulated-lightning impulse conditions.1.2 Procedures are given for tests using standard 1.2 by 50s full-wave impulses.1.3 This test method is intended for use in determining theimpulse dielectric strength of ins
4、ulating materials, either usingsimple electrodes or functional models. It is not intended foruse in impulse testing of apparatus.1.4 This test method is similar to IEC Publication 243-3.Allprocedures in this test method are included in IEC 243-3.Differences between this test method and IEC 243-3 are
5、 largelyeditorial.1.5 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 u
6、se. Specific precautionstatements are given in Section 9.2. Referenced Documents2.1 ASTM Standards:2D 149 Test Method for Dielectric Breakdown Voltage andDielectric Strength of Solid Electrical Insulating Materialsat Commercial Power FrequenciesD 374 Test Methods for Thickness of Solid Electrical In
7、su-lationD 2413 Test Methods for Preparation of Insulating Paperand Board Impregnated with a Liquid Dielectric2.2 American National Standard:C 68.1 Techniques for Dielectric Tests (IEEE Standard No.4)32.3 IEC Standard:Pub 243-3 Methods of Test for Electric Strength of SolidInsulating MaterialsPart 3
8、:Additional Requirements forImpulse Tests33. Terminology3.1 Definitions: Reference should be made to Fig. 1 for thesymbols mentioned.3.1.1 full-impulse-voltage wave, nan aperiodic transientvoltage that rises rapidly to a maximum value, then falls lessrapidly to zero.3.1.2 peak value of an impulse vo
9、ltage wave, nthe maxi-mum value of voltage.3.1.3 virtual-peak value of an impulse voltage wave, navalue derived from a recording of an impulse wave on whichhigh-frequency oscillations or overshoot of limited magnitudemay be present. If the oscillations have a magnitude of no morethan 5 % of the peak
10、 value and a frequency of at least 0.5 MHz,a mean curve may be drawn, the maximum amplitude of whichis the virtual-peak value. If the oscillations are of greatermagnitude, the voltage wave is not acceptable for standardtests.3.1.4 virtual-front time of an impulse voltage wave,nequal to 1.67 times th
11、e interval tfbetween the instants whenthe voltage is 0.3 and 0.9 times the peak value (t1, Fig. 1).3.1.5 virtual origin of an impulse voltage wave, nthepoint of intersection O1with the line of zero voltage of a linedrawn through the points of 0.3 and 0.9 times the peak voltageon the front of an impu
12、lse voltage wave.3.1.6 virtual time to half-value of an impulse voltage wave,nthe time interval t2between the virtual origin O1and theinstant on the tail when the voltage has decreased to half thepeak value.1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic
13、 Insulating Materials and is the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved March 1, 2004. Published March 2004. Originallyapproved in 1975. Last previous edition approved in 1997 as D 3426 97.2For referenced ASTM standards, visit the ASTM website, www.a
14、stm.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.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM
15、 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 A series of sets-of-three voltage waves of a specifiedshape (see 5.3) is applied to the test specimen. The voltage ofsuccessive sets is increased in magnitude until breakd
16、own ofthe test specimen occurs.4.2 The procedures for sampling and specimen preparationare as specified in the material specification or other documentcalling for the use of this test method. The surroundingmedium (air or other gas, or oil or other liquid) is also asspecified if it differs from the
17、medium in which the specimensare finally conditioned for test.5. Significance and Use5.1 Insulating materials used in high-voltage equipmentmay be subjected to transient voltage stresses, resulting fromsuch causes as nearby lightning strokes. This is particularlytrue of apparatus such as transformer
18、s and switchgear used inelectrical-power transmission and distribution systems. Theability of insulating materials to withstand these transientvoltages is important in establishing the reliability of apparatusinsulated with these materials.5.2 Transient voltages caused by lightning may be of eitherp
19、ositive or negative polarity. In a symmetrical field betweenidentical electrodes, the polarity has no effect on the break-down strength. However, with dissimilar electrodes there maybe a pronounced polarity effect. It is common practice whenusing dissimilar electrodes, to make negative that electrod
20、e atwhich the higher gradient will appear. When asymmetricalelectrodes are used for testing materials with which the testerhas no previous experience or knowledge, it is recommendedthat he make comparative tests with positive polarity andnegative polarity applied to the higher gradient, or smallerel
21、ectrode, to determine which polarity produces the lowerbreakdown voltage.5.3 The standard wave shape is a 1.2 by 50-s wave,reaching peak voltage in approximately 1.2 s and decaying to50 % of peak voltage in approximately 50 s after thebeginning of the wave. This wave is intended to simulate alightni
22、ng stroke that may strike a system without causingfailure on the system.5.4 For most materials, the impulse dielectric strength willbe higher than either its power frequency alternating voltage orits direct voltage dielectric strengths. Because of the short timeinvolved, dielectric heating and other
23、 thermal effects arelargely eliminated during impulse testing. Thus, the impulsetest gives values closer to the intrinsic breakdown strength thando longer time tests. From comparisons of the impulse dielec-tric strength with the values obtained from longer time tests,inferences may be drawn as to th
24、e modes of failures under theFIG. 1 Full-Impulse Voltage WaveD 3426 97 (2004)2various tests for a given material.Appendix X1 of Test MethodD 149 should be referred to for further information on thissubject.6. Apparatus6.1 Impulse Generator, capable of applying to the testspecimen a standard 1.2 by 5
25、0-s wave of either positive ornegative polarity. The virtual front time shall be 1.2 s 6 30 %and the virtual time to half value 50 s 6 20 %. The maximumvoltage and the energy-storage capability must be sufficient toprovide impulse waves of the proper shape to any specimen tobe tested up to the break
26、down voltage (or specified proofvoltage) of the material. The electrical characteristics (particu-larly capacitance) of the test specimen may have a significanteffect on the magnitude and shape of the applied voltage wave,especially when using generators having low energy-storagecapability. In such
27、cases, provisions must be made for moni-toring and adjusting the voltage wave shape.6.2 Voltage-Measurement Equipment, meeting the require-ments of ANSI C 68.1.6.3 Electrodes:6.3.1 Electrodes shall be as defined in the specification ormethod in which reference is made to this test method. If noelect
28、rodes are specified, one of the types listed in Table 1 ofTest Method D 149 should be used when testing materials aslisted in Table 1 of Test Method D 149.6.3.2 The surfaces of the electrodes must be polished andfree of projecting irregularities resulting from previous tests.6.4 Surrounding Medium,
29、as specified for the material beingtested. If the surrounding medium is not specified, refer to 8.2and 8.3 and to the section on Surrounding Medium in TestMethod D 149 for guidance.7. Sampling7.1 Sample in accordance with the requirements given in thedocument in which this test method is specified.7
30、.2 Sample in such a manner as to permit preparation of testspecimens that are representative of the lot or other unit ofmaterial being evaluated.7.3 Handle and store the samples (and specimens preparedfrom the samples) in a manner to prevent alteration of theproperties of the material due to such ha
31、ndling and storage.8. Test Specimens8.1 Prepare specimens of sufficient number and size topermit making five valid tests (see 9.2.4).8.2 Prepare the specimens for test using procedures asspecified in the material specification. (In general, materialsshould be tested in the medium in which they are t
32、o be used,after conditioning in a manner representative of the manufac-turing methods to which they will be subjected.)8.3 When testing specimens in a surrounding medium otherthan air, do not remove them from that surrounding mediumsubsequent to final conditioning for test until after completionof t
33、he test. As a specific example, when conditioning speci-mens for testing in oil by vacuum-impregnation with oil do notremove the specimen from oil even momentarily prior totesting.9. Procedure9.1 WarningLethal voltages are a potential hazard duringthe performance of this test. It is essential that t
34、he testapparatus, and all associated equipment electrically connectedto it, be properly designed and installed for safe operation.Solidly ground all electrically conductive parts which it ispossible for a person to contact during the test. Provide meansfor use at the completion of any test to ground
35、 any parts whichwere at high voltage during the test or have the potential foracquiring an induced charge during the test or retaining acharge even after disconnection of the voltage source. Thor-oughly instruct all operators as to the correct procedures forperforming tests safely. When making high
36、voltage tests,particularly in compressed gas or in oil, it is possible for theenergy released at breakdown to be sufficient to result in fire,explosion, or rupture of the test chamber. Design test equip-ment, test chambers, and test specimens so as to minimize thepossibility of such occurrences and
37、to eliminate the possibilityof personal injury. If the potential for fire exists, have firesuppression equipment available.9.2 Voltage Application:9.2.1 Place the specimen between the electrodes and applywaves of the polarity specified. The initial peak voltage shall beapproximately 70 % of the expe
38、cted breakdown voltage.9.2.2 Apply the impulse waves in sets of three waves, eachset at successively increasing voltage levels until breakdownoccurs. Each level of peak voltage shall be higher than thepreceding level by from 5 to 10 % of the crest voltage of theinitial level.9.2.3 The minimum time b
39、etween successive voltage appli-cations is dependent upon the charging time constant of thegenerator and should be three times the time constant.9.2.4 A valid test is one in which impulse waves are appliedfor at least two levels without breakdown before breakdownoccurs at the third or some higher vo
40、ltage level.9.3 Criteria of Breakdown:9.3.1 Observation of actual rupture, either visually or audi-bly, may be the most immediate indication of failure. For somespecimen configurations, observation of the impulse wave onan oscilloscope may be the most sensitive indication. Acollapse of the voltage w
41、ave at any point is an indication offailure either by puncture or surface creepage.9.3.2 The impulse dielectric breakdown voltage is the peakvoltage that the wave causing breakdown would have reachedhad breakdown not occurred.9.4 ThicknessMeasure the average thickness of the speci-men in the area be
42、tween the electrodes, using procedures givenin Test Methods D 374 for the material being tested.10. Calculation10.1 Calculate the impulse-withstand strength using thespecimen thickness and the value for the maximum level ofimpulse voltage that did not cause failure of the specimen.10.2 Calculate the
43、 impulse-breakdown dielectric strengthusing the specimen thickness and the value for impulsedielectric breakdown voltage.D 3426 97 (2004)311. Report11.1 Report the following:11.1.1 Identification of test sample,11.1.2 For each specimen:11.1.2.1 Average thickness,11.1.2.2 Maximum impulse-withstand vo
44、ltage,11.1.2.3 Impulse dielectric breakdown voltage,NOTE 1It may in some cases be desirable to report which of the threeimpulse waves at the breakdown level resulted in failure.11.1.2.4 Impulse-withstand strength,11.1.3 For each sample:11.1.3.1 Average impulse-withstand strength,11.1.3.2 Average imp
45、ulse dielectric breakdown strength,11.1.3.3 Indication of variability, preferably the standarddeviation, from the average dielectric strengths,11.1.4 Conditioning or specimen preparation,11.1.5 Ambient atmospheric temperature,11.1.6 Surrounding medium,11.1.7 Test temperature,11.1.8 Impulse wave pola
46、rity,11.1.9 Initial voltage level and magnitude of voltage steps,and11.1.10 Date of test.12. Precision and Bias12.1 The precision and bias for this test method have notbeen established.12.2 Tests made by one operator in a single laboratory,using one test set over a period of 18 months, on 15 sets of
47、 5randomized specimens from a single reference sample, resultedin a repeatability within 6 5 %. The sample was 0.002-in(50-m) thick high-density capacitor tissue. The specimenswere made up of three layers and were impregnated with oilprior to test in accordance with Test Methods D 2413. Thespecimens
48、 were tested under oil, using Type 1 electrodes. Theaverage impulse breakdown strength for the 15 sets of speci-mens ranged from 4200 to 4600 V/mil (165 to 181 kV/mm).13. Keywords13.1 dielectric breakdown; dielectric breakdown criteria;dielectric breakdown voltage; dielectric strength; full-impulse-
49、voltage wave; impulse dielectric strength; impulse generator;impulse waves; lightning strokes; peak value; simulated-lightning impulse; solid insulating material; virtual front time;virtual origin; virtual peak value; virtual time to half-valueASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own respon
