1、Designation: D 149 97a (Reapproved 2004)An American National StandardStandard Test Method forDielectric Breakdown Voltage and Dielectric Strength ofSolid Electrical Insulating Materials at Commercial PowerFrequencies1This standard is issued under the fixed designation D 149; the number immediately f
2、ollowing 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 (e) indicates an editorial change since the last revision or reapproval.This standard has been a
3、pproved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers procedures for the determina-tion of dielectric strength of solid insulating materials atcommercial power frequencies, under specified conditions.2,31.2 Unless otherwise specified, the tests shall be made at
4、 60Hz. However, this test method may be used at any frequencyfrom 25 to 800 Hz. At frequencies above 800 Hz, dielectricheating may be a problem.1.3 This test method is intended to be used in conjunctionwith any ASTM standard or other document that refers to thistest method. References to this docume
5、nt should specify theparticular options to be used (see 5.5).1.4 It may be used at various temperatures, and in anysuitable gaseous or liquid surrounding medium.1.5 This test method is not intended for measuring thedielectric strength of materials that are fluid under the condi-tions of test.1.6 Thi
6、s test method is not intended for use in determiningintrinsic dielectric strength, direct-voltage dielectric strength,or thermal failure under electrical stress (see Test MethodD 3151).1.7 This test method is most commonly used to determinethe dielectric breakdown voltage through the thickness of a
7、testspecimen (puncture). It may also be used to determine dielec-tric breakdown voltage along the interface between a solidspecimen and a gaseous or liquid surrounding medium (flash-over). With the addition of instructions modifying Section 12,this test method may be used for proof testing.1.8 This
8、test method is similar to IEC Publication 243-1. Allprocedures in this method are included in IEC 243-1. Differ-ences between this method and IEC 243-1 are largely editorial.1.9 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibil
9、ity 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. Specific hazardstatements are given in Section 7. Also see 6.4.1.2. Referenced Documents2.1 ASTM Standards:4D 374 Test Methods for Thickness
10、 of Solid Electrical Insu-lationD 618 Practice for Conditioning Plastics for TestingD 877 Test Method for Dielectric Breakdown Voltage ofInsulating Liquids Using Disk ElectrodesD 1711 Terminology Relating to Electrical InsulationD 2413 Practice for Preparation of Insulating Paper andBoard Impregnate
11、d with a Liquid DielectricD 3151 Test Method for Thermal Failure of Solid ElectricalInsulating Materials Under Electric StressD 3487 Specification for Mineral Insulating Oil Used inElectrical ApparatusD 5423 Specification for Forced-Convection LaboratoryOvens for Electrical Insulation2.2 IEC Standar
12、d:Pub. 243-1 Methods of Test for Electrical Strength of SolidInsulating MaterialsPart 1: Tests at Power Frequencies51This 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
13、Tests.Current edition approved March 1, 2004. Published March 2004. Originallyapproved in 1922. Last previous edition approved in 1997 as D 149 97a.2Bartnikas, R., Chapter 3, “High Voltage Measurements,” Electrical Propertiesof Solid Insulating Materials, Measurement Techniques, Vol. IIB, Engineerin
14、gDielectrics, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987.3Nelson, J. K., Chapter 5, “Dielectric Breakdown of Solids,” ElectricalProperties of Solid Insulating Materials: Molecular Structure and ElectricalBehavior, Vol. IIA, Engineering Dielectrics, R. Bartnikas and R. M. Eichorn,Ed
15、itors, ASTM STP 783, ASTM, Philadelphia, 1983.4For 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.5Available from
16、 the International Electrotechnical Commission, Geneva, Swit-zerland.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.3 ANSI Standard:C68.1 Techniques for Dielectric Tests, IEEE Standard No.463. Terminology3.1 Definitions:3.1.1 diel
17、ectric breakdown voltage (electric breakdownvoltage), nthe potential difference at which dielectric failureoccurs under prescribed conditions in an electrical insulatingmaterial located between two electrodes. (See also AppendixX1.)3.1.1.1 DiscussionThe term dielectric breakdown voltageis sometimes
18、shortened to “breakdown voltage.”3.1.2 dielectric failure (under test), nan event that isevidenced by an increase in conductance in the dielectric undertest limiting the electric field that can be sustained.3.1.3 dielectric strength, nthe voltage gradient at whichdielectric failure of the insulating
19、 material occurs under spe-cific conditions of test.3.1.4 electric strength, nsee dielectric strength.3.1.4.1 DiscussionInternationally, “electric strength” isused almost universally.3.1.5 flashover, na disruptive electrical discharge at thesurface of electrical insulation or in the surrounding medi
20、um,which may or may not cause permanent damage to theinsulation.3.1.6 For definitions of other terms relating to solid insulat-ing materials, refer to Terminology D 1711.4. Summary of Test Method4.1 Alternating voltage at a commercial power frequency(60 Hz, unless otherwise specified) is applied to
21、a testspecimen. The voltage is increased from zero or from a levelwell below the breakdown voltage, in one of three prescribedmethods of voltage application, until dielectric failure of thetest specimen occurs.4.2 Most commonly, the test voltage is applied using simpletest electrodes on opposite fac
22、es of specimens. The specimensmay be molded or cast, or cut from flat sheet or plate. Otherelectrode and specimen configurations may be used to accom-modate the geometry of the sample material, or to simulate aspecific application for which the material is being evaluated.5. Significance and Use5.1
23、The dielectric strength of an electrical insulating mate-rial is a property of interest for any application where anelectrical field will be present. In many cases the dielectricstrength of a material will be the determining factor in thedesign of the apparatus in which it is to be used.5.2 Tests ma
24、de as specified herein may be used to providepart of the information needed for determining suitability of amaterial for a given application; and also, for detecting changesor deviations from normal characteristics resulting from pro-cessing variables, aging conditions, or other manufacturing orenvi
25、ronmental situations. This test method is useful for processcontrol, acceptance or research testing.5.3 Results obtained by this test method can seldom be useddirectly to determine the dielectric behavior of a material in anactual application. In most cases it is necessary that theseresults be evalu
26、ated by comparison with results obtained fromother functional tests or from tests on other materials, or both,in order to estimate their significance for a particular material.5.4 Three methods for voltage application are specified inSection 12: Method A, Short-Time Test; Method B, Step-by-Step Test
27、; and Method C, Slow Rate-of-Rise Test. Method A isthe most commonly-used test for quality-control tests. How-ever, the longer-time tests, Methods B and C, which usuallywill give lower test results, may give more meaningful resultswhen different materials are being compared with each other. Ifa test
28、 set with motor-driven voltage control is available, theslow rate-of-rise test is simpler and preferable to the step-by-step test. The results obtained from Methods B and C arecomparable to each other.5.5 Documents specifying the use of this test method shallalso specify:5.5.1 Method of voltage appl
29、ication,5.5.2 Voltage rate-of-rise, if slow rate-of-rise method isspecified,5.5.3 Specimen selection, preparation, and conditioning,5.5.4 Surrounding medium and temperature during test,5.5.5 Electrodes,5.5.6 Wherever possible, the failure criterion of the current-sensing element, and5.5.7 Any desire
30、d deviations from the recommended proce-dures as given.5.6 If any of the requirements listed in 5.5 are missing fromthe specifying document, then the recommendations for theseveral variables shall be followed.5.7 Unless the items listed in 5.5 are specified, tests madewith such inadequate reference
31、to this test method are not inconformance with this test method. If the items listed in 5.5 arenot closely controlled during the test, the precisions stated in15.2 and 15.3 may not be realized.5.8 Variations in the failure criteria (current setting andresponse time) of the current sensing element si
32、gnificantlyaffect the test results.5.9 Appendix X1. contains a more complete discussion ofthe significance of dielectric strength tests.6. Apparatus6.1 Voltage SourceObtain the test voltage from a step-uptransformer supplied from a variable sinusoidal low-voltagesource. The transformer, its voltage
33、source, and the associatedcontrols shall have the following capabilities:6.1.1 The ratio of crest to root-mean-square (rms) testvoltage shall be equal to=2 6 5 % (1.34 to 1.48), with thetest specimen in the circuit, at all voltages greater than 50 % ofthe breakdown voltage.6.1.2 The capacity of the
34、source shall be sufficient tomaintain the test voltage until dielectric breakdown occurs. Formost materials, using electrodes similar to those shown inTable 1, an output current capacity of 40 mA is usuallysatisfactory. For more complex electrode structures, or for6Available from American National S
35、tandards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.D 149 97a (2004)2testing high-loss materials, higher current capacity may beneeded. The power rating for most tests will vary from 0.5 kVAfor testing low-capacitance specimens at voltages up to 10 kV,to 5 kVA for voltages up to
36、100 kV.6.1.3 The controls on the variable low-voltage source shallbe capable of varying the supply voltage and the resultant testvoltage smoothly, uniformly, and without overshoots or tran-sients, in accordance with 12.2. Do not allow the peak voltageto exceed 1.48 times the indicated rms test volta
37、ge under anycircumstance. Motor-driven controls are preferable for makingshort-time (see 12.2.1) or slow-rate-of-rise (see 12.2.3) tests.6.1.4 Equip the voltage source with a circuit-breakingdevice that will operate within three cycles. The device shalldisconnect the voltage-source equipment from th
38、e powerservice and protect it from overload as a result of specimenbreakdown causing an overload of the testing apparatus. Ifprolonged current follows breakdown it will result in unnec-essary burning of the test specimens, pitting of the electrodes,and contamination of any liquid surrounding medium.
39、6.1.5 The circuit-breaking device should have an adjustablecurrent-sensing element in the step-up transformer secondary,to allow for adjustment consistent with the specimen charac-teristics and arranged to sense specimen current. Set thesensing element to respond to a current that is indicative ofsp
40、ecimen breakdown as defined in 12.3.6.1.6 The current setting can have a significant effect on thetest results. Make the setting high enough that transients, suchas partial discharges, will not trip the breaker but not so highthat excessive burning of the specimen, with resultant electrodedamage, wi
41、ll occur on breakdown. The optimum currentsetting is not the same for all specimens and depending uponthe intended use of the material and the purpose of the test, itmay be desirable to make tests on a given sample at more thanone current setting. The electrode area may have a significanteffect upon
42、 what the current setting should be.6.1.7 The specimen current-sensing element may be in theprimary of the step-up transformer. Calibrate the current-sensing dial in terms of specimen current.6.1.8 Exercise care in setting the response of the currentcontrol. If the control is set too high, the circu
43、it will notrespond when breakdown occurs; if set too low, it may respondto leakage currents, capacitive currents, or partial discharge(corona) currents or, when the sensing element is located in theprimary, to the step-up transformer magnetizing current.6.2 Voltage MeasurementA voltmeter must be pro
44、videdfor measuring the rms test voltage. A peak-reading voltmetermay be used, in which case divide the reading by=2togetrms values. The overall error of the voltage-measuring circuitshall not exceed 5 % of the measured value. In addition, theresponse time of the voltmeter shall be such that its time
45、 lagwill not be greater than 1 % of full scale at any rate-of-riseused.6.2.1 Measure the voltage using a voltmeter or potentialtransformer connected to the specimen electrodes, or to aseparate voltmeter winding, on the test transformer, that isunaffected by the step-up transformer loading.6.2.2 It i
46、s desirable for the reading of the maximum appliedtest voltage to be retained on the voltmeter after breakdown sothat the breakdown voltage can be accurately read and re-corded.6.3 ElectrodesFor a given specimen configuration, thedielectric breakdown voltage may vary considerably, depend-ing upon th
47、e geometry and placement of the test electrodes. Forthis reason it is important that the electrodes to be used bedescribed when specifying this test method, and that they bedescribed in the report.TABLE 1 Typical Electrodes for Dielectric Strength Testing of Various Types of Insulating MaterialsAEle
48、ctrodeTypeDescription of ElectrodesB,CInsulating Materials1 Opposing cylinders 51 mm (2 in.) in diameter, 25 mm (1 in.) thick withedges rounded to 6.4 mm (0.25 in.) radiusflat sheets of paper, films, fabrics, rubber, molded plastics, laminates,boards, glass, mica, and ceramic2 Opposing cylinders 25
49、mm (1 in.) in diameter, 25 mm (1 in.) thick withedges rounded to 3.2 mm (0.125 in.) radiussame as for Type 1, particularly for glass, mica, plastic, and ceramic3 Opposing cylindrical rods 6.4 mm (0.25 in.) in diameter with edgesrounded to 0.8 mm (0.0313 in.) radiusDsame as for Type 1, particularly for varnish, plastic, and other thin film andtapes: where small specimens necessitate the use of smaller electrodes,or where testing of a small area is desired4 Flat plates 6.4 mm (0.25 in.) wide and 108 mm (4.25 in.) long with edgessquare and ends rounded to 3.2 mm (0.125 in.) r
