ASTM D149-09(2013)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
Designation: D149 − 09 (Reapproved 2013)
Standard Test Method for
Dielectric Breakdown Voltage and Dielectric Strength of
Solid Electrical Insulating Materials at Commercial Power
Frequencies
This standard is issued under the fixed designation D149; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript 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. Scope* dielectric breakdown voltage along the interface between a
solid specimen and a gaseous or liquid surrounding medium
1.1 This test method covers procedures for the determina-
(flashover). With the addition of instructions modifying Sec-
tion of dielectric strength of solid insulating materials at
2,3 tion 12, this test method is also suitable for use for proof
commercial power frequencies, under specified conditions.
testing.
1.2 Unless otherwise specified, the tests shall be made at 60
1.8 ThistestmethodissimilartoIECPublication243-1.All
Hz. However, this test method is suitable for use at any
procedures in this method are included in IEC 243-1. Differ-
frequency from 25 to 800 Hz. At frequencies above 800 Hz,
encesbetweenthismethodandIEC243-1arelargelyeditorial.
dielectric heating is a potential problem.
1.9 This standard does not purport to address all of the
1.3 This test method is intended to be used in conjunction
safety concerns, if any, associated with its use. It is the
with anyASTM standard or other document that refers to this
responsibility of the user of this standard to establish appro-
test method. References to this document need to specify the
priate safety and health practices and determine the applica-
particular options to be used (see 5.5).
bility of regulatory limitations prior to use. Specific hazard
1.4 It is suitable for use at various temperatures, and in any
statements are given in Section 7. Also see 6.4.1.
suitable gaseous or liquid surrounding medium.
2. Referenced Documents
1.5 This test method is not intended for measuring the
2.1 ASTM Standards:
dielectric strength of materials that are fluid under the condi-
D374Test Methods for Thickness of Solid Electrical Insu-
tions of test.
lation (Withdrawn 2013)
1.6 This test method is not intended for use in determining
D618Practice for Conditioning Plastics for Testing
intrinsic dielectric strength, direct-voltage dielectric strength,
D877Test Method for Dielectric Breakdown Voltage of
or thermal failure under electrical stress (see Test Method
Insulating Liquids Using Disk Electrodes
D3151).
D1711Terminology Relating to Electrical Insulation
1.7 This test method is most commonly used to determine
D2413Practice for Preparation of Insulating Paper and
thedielectricbreakdownvoltagethroughthethicknessofatest
Board Impregnated with a Liquid Dielectric
specimen (puncture). It is also suitable for use to determine
D3151Test Method for Thermal Failure of Solid Electrical
Insulating Materials Under Electric Stress (Withdrawn
2007)
This test method is under the jurisdiction of ASTM Committee D09 on
D3487Specification for Mineral Insulating Oil Used in
Electrical and Electronic Insulating Materials and is the direct responsibility of
Electrical Apparatus
Subcommittee D09.12 on Electrical Tests.
Current edition approved April 1, 2013. Published April 2013. Originally D5423Specification for Forced-Convection Laboratory Ov-
approved in 1922. Last previous edition approved in 2009 as D149–09. DOI:
ens for Evaluation of Electrical Insulation
10.1520/D0149-09R13.
Bartnikas, R., Chapter 3, “High Voltage Measurements,” Electrical Properties
of Solid Insulating Materials, Measurement Techniques , Vol. IIB, Engineering For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Dielectrics, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987 . contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Nelson, J. K., Chapter 5, “Dielectric Breakdown of Solids,” Electrical Standards volume information, refer to the standard’s Document Summary page on
Properties of Solid Insulating Materials: Molecular Structure and Electrical the ASTM website.
Behavior, Vol. IIA, Engineering Dielectrics, R. Bartnikas and R. M. Eichorn, The last approved version of this historical standard is referenced on
Editors, ASTM STP 783, ASTM, Philadelphia, 1983 www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D149 − 09 (2013)
2.2 IEC Standard: strength of a material will be the determining factor in the
Pub. 243-1Methods of Test for Electrical Strength of Solid design of the apparatus in which it is to be used.
Insulating Materials—Part 1:Tests at Power Frequencies
5.2 Tests made as specified herein are suitable for use to
2.3 ANSI Standard:
provide part of the information needed for determining suit-
C68.1 Techniques for Dielectric Tests, IEEE Standard No.
ability of a material for a given application; and also, for
detecting changes or deviations from normal characteristics
resulting from processing variables, aging conditions, or other
3. Terminology
manufacturing or environmental situations.This test method is
3.1 Definitions: useful for process control, acceptance or research testing.
3.1.1 dielectric breakdown voltage (electric breakdown
5.3 Resultsobtainedbythistestmethodcanseldombeused
voltage), n—the potential difference at which dielectric failure
directly to determine the dielectric behavior of a material in an
occurs under prescribed conditions in an electrical insulating
actual application. In most cases it is necessary that these
material located between two electrodes. (See also Appendix
results be evaluated by comparison with results obtained from
X1.)
other functional tests or from tests on other materials, or both,
3.1.1.1 Discussion—The term dielectric breakdown voltage
in order to estimate their significance for a particular material.
is sometimes shortened to “breakdown voltage.”
5.4 Three methods for voltage application are specified in
3.1.2 dielectric failure (under test), n—an event that is
Section 12: Method A, Short-Time Test; Method B, Step-by-
evidencedbyanincreaseinconductanceinthedielectricunder
StepTest; and Method C, Slow Rate-of-RiseTest. MethodAis
test limiting the electric field that can be sustained.
the most commonly-used test for quality-control tests.
3.1.3 dielectric strength, n—the voltage gradient at which
However, the longer-time tests, Methods B and C, which
dielectric failure of the insulating material occurs under spe-
usually will give lower test results, will potentially give more
cific conditions of test.
meaningful results when different materials are being com-
3.1.4 electric strength, n—see dielectric strength. pared with each other. If a test set with motor-driven voltage
3.1.4.1 Discussion—Internationally, “electric strength” is control is available, the slow rate-of-rise test is simpler and
used almost universally. preferable to the step-by-step test. The results obtained from
Methods B and C are comparable to each other.
3.1.5 flashover, n—a disruptive electrical discharge at the
surface of electrical insulation or in the surrounding medium,
5.5 Documents specifying the use of this test method shall
which may or may not cause permanent damage to the
also specify:
insulation.
5.5.1 Method of voltage application,
5.5.2 Voltage rate-of-rise, if slow rate-of-rise method is
3.1.6 For definitions of other terms relating to solid insulat-
specified,
ing materials, refer to Terminology D1711.
5.5.3 Specimen selection, preparation, and conditioning,
4. Summary of Test Method 5.5.4 Surrounding medium and temperature during test,
5.5.5 Electrodes,
4.1 Alternating voltage at a commercial power frequency
5.5.6 Wherever possible, the failure criterion of the current-
(60 Hz, unless otherwise specified) is applied to a test
sensing element, and
specimen. The voltage is increased from zero or from a level
5.5.7 Any desired deviations from the recommended proce-
well below the breakdown voltage, in one of three prescribed
dures as given.
methods of voltage application, until dielectric failure of the
test specimen occurs.
5.6 If any of the requirements listed in 5.5 are missing from
the specifying document, then the recommendations for the
4.2 Mostcommonly,thetestvoltageisappliedusingsimple
several variables shall be followed.
test electrodes on opposite faces of specimens.The options for
the specimens are that they be molded or cast, or cut from flat
5.7 Unless the items listed in 5.5 are specified, tests made
sheetorplate.Otherelectrodeandspecimenconfigurationsare
with such inadequate reference to this test method are not in
also suitable for use to accommodate the geometry of the
conformancewiththistestmethod.Iftheitemslistedin5.5are
samplematerial,ortosimulateaspecificapplicationforwhich
not closely controlled during the test, it is possible that the
the material is being evaluated.
precisions stated in 15.2 and 15.3 will not be obtained.
5.8 Variations in the failure criteria (current setting and
5. Significance and Use
response time) of the current sensing element significantly
5.1 The dielectric strength of an electrical insulating mate-
affect the test results.
rial is a property of interest for any application where an
5.9 Appendix X1. contains a more complete discussion of
electrical field will be present. In many cases the dielectric
the significance of dielectric strength tests.
Available from International Electrotechnical Commission (IEC), 3 rue de 6. Apparatus
Varembé, Case postale 131, CH-1211, Geneva 20, Switzerland, http://www.iec.ch.
6.1 Voltage Source—Obtain the test voltage from a step-up
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. transformer supplied from a variable sinusoidal low-voltage
D149 − 09 (2013)
source. The transformer, its voltage source, and the associated 6.1.5 It is important for the circuit-breaking device to have
controls shall have the following capabilities: an adjustable current-sensing element in the step-up trans-
6.1.1 The ratio of crest to root-mean-square (rms) test former secondary, to allow for adjustment consistent with the
specimen characteristics and arranged to sense specimen cur-
voltage shall be equal to =265% 1.34 to1.48 , with the test
~ !
rent. Set the sensing element to respond to a current that is
specimen in the circuit, at all voltages greater than 50% of the
indicative of specimen breakdown as defined in 12.3.
breakdown voltage.
6.1.6 Thecurrentsettingislikelytohaveasignificanteffect
6.1.2 The capacity of the source shall be sufficient to
onthetestresults.Makethesettinghighenoughthattransients,
maintainthetestvoltageuntildielectricbreakdownoccurs.For
such as partial discharges, will not trip the breaker but not so
most materials, using electrodes similar to those shown in
high that excessive burning of the specimen, with resultant
Table 1, an output current capacity of 40 mA is usually
electrode damage, will occur on breakdown. The optimum
satisfactory. For more complex electrode structures, or for
currentsettingisnotthesameforallspecimensanddepending
testing high-loss materials, it is possible that higher current
upon the intended use of the material and the purpose of the
capacity will be needed. The power rating for most tests will
test, it is often desirable to make tests on a given sample at
vary from 0.5 kVA for testing low-capacitance specimens at
more than one current setting. The electrode area is likely to
voltages up to 10 kV, to 5 kVA for voltages up to 100 kV.
have a significant effect upon the choice of current setting.
6.1.3 The controls on the variable low-voltage source shall
6.1.7 It is possible that the specimen current-sensing ele-
be capable of varying the supply voltage and the resultant test
ment will be in the primary of the step-up transformer.
voltage smoothly, uniformly, and without overshoots or
Calibratethecurrent-sensingdialintermsofspecimencurrent.
transients, in accordance with 12.2. Do not allow the peak
6.1.8 Exercise care in setting the response of the current
voltage to exceed 1.48 times the indicated rms test voltage
control. If the control is set too high, the circuit will not
under any circumstance. Motor-driven controls are preferable
respond when breakdown occurs; if set too low, it is possible
for making short-time (see 12.2.1) or slow-rate-of-rise (see
that it will respond to leakage currents, capacitive currents, or
12.2.3) tests.
partial discharge (corona) currents or, when the sensing ele-
6.1.4 Equip the voltage source with a circuit-breaking
ment is located in the primary, to the step-up transformer
device that will operate within three cycles. The device shall
magnetizing current.
disconnect the voltage-source equipment from the power
6.2 Voltage Measurement—A voltmeter must be provided
service and protect it from overload as a result of specimen
for measuring the rms test voltage. If a peak-reading voltmeter
breakdown causing an overload of the testing apparatus. If
prolonged current follows breakdown it will result in unnec- is used, divide the reading by =2 to get rms values. The
essary burning of the test specimens, pitting of the electrodes, overall error of the voltage-measuring circuit shall not exceed
and contamination of any liquid surrounding medium. 5% of the measured value. In addition, the response time of
A
TABLE 1 Typical Electrodes for Dielectric Strength Testing of Various Types of Insulating Materials
Electrode
B,C
Description of Electrodes Insulating Materials
Type
1 Opposing cylinders 51 mm (2 in.) in diameter, 25 mm (1 in.) thick with flat sheets of paper, films, fabrics, rubber, molded plastics, laminates,
edges rounded to 6.4 mm (0.25 in.) radius boards, glass, mica, and ceramic
2 Opposing cylinders 25 mm (1 in.) in diameter, 25 mm (1 in.) thick with same as for Type 1, particularly for glass, mica, plastic, and ceramic
edges rounded to 3.2 mm (0.125 in.) radius
3 Opposing cylindrical rods 6.4 mm (0.25 in.) in diameter with edges same as for Type 1, particularly for varnish, plastic, and other thin film and
D
rounded to 0.8 mm (0.0313 in.) radius tapes: where small specimens necessitate the use of smaller electrodes,
or where testing of a small area is desired
4 Flat plates 6.4 mm (0.25 in.) wide and 108 mm (4.25 in.) long with edges same a
...