ASTM D3426-97
(Test Method)Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials Using Impulse Waves
Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials Using Impulse Waves
SCOPE
1.1 This test method covers the determination of dielectric strength of solid electrical insulating materials under simulated-lightning impulse conditions.
1.2 Procedures are given for tests using standard 1.2 by 50 [mu]s full-wave impulses.
1.3 This test method is intended for use in determining the impulse dielectric strength of insulating materials, either using simple electrodes or functional models. It is not intended for use in impulse testing of apparatus.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precaution statements are given in Section 9.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
An American National Standard
Designation:D3426–97
Standard Test Method for
Dielectric Breakdown Voltage and Dielectric Strength of
Solid Electrical Insulating Materials Using Impulse Waves
This standard is issued under the fixed designation D 3426; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope C 68.1 Techniques for Dielectric Tests (IEEE Standard No.
4)
1.1 This test method covers the determination of dielectric
2.3 IEC Standard:
strength of solid electrical insulating materials under
Pub 243-3 Methods of Test for Electric Strength of Solid
simulated-lightning impulse conditions.
Insulating Materials—Part 3:Additional Requirements for
1.2 Procedures are given for tests using standard 1.2 by 50
Impulse Tests
µs full-wave impulses.
1.3 This test method is intended for use in determining the
3. Terminology
impulse dielectric strength of insulating materials, either using
3.1 Definitions: Reference should be made to Fig. 1 for the
simple electrodes or functional models. It is not intended for
symbols mentioned.
use in impulse testing of apparatus.
3.1.1 full-impulse-voltage wave, n—an aperiodic transient
1.4 This test method is similar to IEC Publication 243-3.All
voltage that rises rapidly to a maximum value, then falls less
procedures in this test method are included in IEC 243-3.
rapidly to zero.
DifferencesbetweenthistestmethodandIEC243-3arelargely
3.1.2 peak value of an impulse voltage wave, n— the
editorial.
maximum value of voltage.
1.5 This standard does not purport to address all of the
3.1.3 virtual-peak value of an impulse voltage wave, n—a
safety concerns, if any, associated with its use. It is the
value derived from a recording of an impulse wave on which
responsibility of the user of this standard to establish appro-
high-frequency oscillations or overshoot of limited magnitude
priate safety and health practices and determine the applica-
maybepresent.Iftheoscillationshaveamagnitudeofnomore
bility of regulatory limitations prior to use. Specific precaution
than5 %ofthepeakvalueandafrequencyofatleast0.5MHz,
statements are given in Section 9.
a mean curve may be drawn, the maximum amplitude of which
2. Referenced Documents is the virtual-peak value. If the oscillations are of greater
magnitude, the voltage wave is not acceptable for standard
2.1 ASTM Standards:
tests.
D 149 Test Method for Dielectric Breakdown Voltage and
3.1.4 virtual-front time of an impulse voltage wave,
Dielectric Strength of Solid Electrical Insulating Materials
2 n—equalto1.67timestheinterval t betweentheinstantswhen
at Commercial Power Frequencies f
the voltage is 0.3 and 0.9 times the peak value (t , Fig. 1).
D 374 Test Methods for Thickness of Solid Electrical Insu-
2 3.1.5 virtual origin of an impulse voltage wave, n—the
lation
point of intersection O with the line of zero voltage of a line
D 2413 Test Methods for Preparation and Electrical Testing
drawn through the points of 0.3 and 0.9 times the peak voltage
of Insulating Paper and Board Impregnated with a Liquid
on the front of an impulse voltage wave.
Dielectric
3.1.6 virtual time to half-value of an impulse voltage wave,
2.2 American National Standard:
n—the time interval t between the virtual origin O and the
2 1
instant on the tail when the voltage has decreased to half the
This test method is under the jurisdiction of ASTM Committee D-9 on
peak value.
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.12 on Electrical Tests.
Current edition approved March 10, 1997. Published February 1998. Originally
published as D 3426 – 75. Last previous edition D 3426 – 95. Available from American National Standards Institute, 11 West 42nd St., 13th
Annual Book of ASTM Standards, Vol 10.01. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
D3426–97
FIG. 1 Full-Impulse Voltage Wave
4. Summary of Test Method be a pronounced polarity effect. It is common practice when
using dissimilar electrodes, to make negative that electrode at
4.1 A series of sets-of-three voltage waves of a specified
which the higher gradient will appear. When asymmetrical
shape (see 5.3) is applied to the test specimen. The voltage of
electrodes are used for testing materials with which the tester
successive sets is increased in magnitude until breakdown of
has no previous experience or knowledge, it is recommended
the test specimen occurs.
that he make comparative tests with positive polarity and
4.2 The procedures for sampling and specimen preparation
are as specified in the material specification or other document negative polarity applied to the higher gradient, or smaller
calling for the use of this test method. The surrounding electrode, to determine which polarity produces the lower
medium (air or other gas, or oil or other liquid) is also as
breakdown voltage.
specified if it differs from the medium in which the specimens
5.3 The standard wave shape is a 1.2 by 50-µs wave,
are finally conditioned for test.
reaching peak voltage in approximately 1.2 µs and decaying to
50 % of peak voltage in approximately 50 µs after the
5. Significance and Use
beginning of the wave. This wave is intended to simulate a
5.1 Insulating materials used in high-voltage equipment
lightning stroke that may strike a system without causing
may be subjected to transient voltage stresses, resulting from
failure on the system.
such causes as nearby lightning strokes. This is particularly
5.4 For most materials, the impulse dielectric strength will
true of apparatus such as transformers and switchgear used in
be higher than either its power frequency alternating voltage or
electrical-power transmission and distribution systems. The
its direct voltage dielectric strengths. Because of the short time
ability of insulating materials to withstand these transient
involved, dielectric heating and other thermal effects are
voltages is important in establishing the reliability of apparatus
largely eliminated during impulse testing. Thus, the impulse
insulated with these materials.
testgivesvaluesclosertotheintrinsicbreakdownstrengththan
5.2 Transient voltages caused by lightning may be of either
do longer time tests. From comparisons of the impulse dielec-
positive or negative polarity. In a symmetrical field between
tric strength with the values obtained from longer time tests,
identical electrodes, the polarity has no effect on the break-
down strength. However, with dissimilar electrodes there may inferences may be drawn as to the modes of failures under the
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
D3426–97
various tests for a given material.Appendix X1 ofTest Method 9. Procedure
D 149 should be referred to for further information on this
9.1 Warning— Lethal voltages are a potential hazard
subject.
during the performance of this test. It is essential that the test
apparatus, and all associated equipment electrically connected
6. Apparatus
to it, be properly designed and installed for safe operation.
6.1 Impulse Generator, capable of applying to the test
Solidly ground all electrically conductive parts which it is
specimen a standard 1.2 by 50-µs wave of either positive or
possible for a person to contact during the test. Provide means
negative polarity. The virtual front time shall be 1.2 µs6 30 %
for use at the completion of any test to ground any parts which
and the virtual time to half value 50 µs 6 20 %.The maximum
were at high voltage during the test or have the potential for
voltage and the energy-storage capability
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.