ASTM D2477-07(2020)
(Test Method)Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Insulating Gases at Commercial Power Frequencies
Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Insulating Gases at Commercial Power Frequencies
SIGNIFICANCE AND USE
4.1 The dielectric breakdown voltage and dielectric strength of an insulating gas in a uniform field depends primarily on the molecular structure of the gas. As different gases are mixed either by plan or by contamination, any change in dielectric breakdown voltage and dielectric strength will depend on both the nature and proportion of the individual gases. This test method uses plane and spherical electrodes which provide a nearly uniform field (see Appendix) in the area of electrical discharge. It is suitable for determining the dielectric breakdown voltage and dielectric strength of different gases and mixtures thereof for research and application evaluations and also as a field test. A more complete discussion of the significance of the dielectric strength test is given in the Appendix.
SCOPE
1.1 This test method covers the determination of the dielectric breakdown voltage and dielectric strength of insulating gases used in transformers, circuit breakers, cables, and similar apparatus as an insulating medium. The test method is applicable only to gases with boiling points below room temperature at atmospheric pressure.
1.2 This standard may involve hazardous materials, operations, and equipment. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.3 Mercury has been designated by EPA and many state agencies as a hazardous material that can cause central nervous system, kidney and liver damage. Mercury, or its vapor, may be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPA's website — http://www.epa.gov/mercury/faq.htm for additional information. Users should be aware that selling mercury and/or mercury containing products into your state may be prohibited by state law.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D2477 − 07 (Reapproved 2020)
Standard Test Method for
Dielectric Breakdown Voltage and Dielectric Strength of
Insulating Gases at Commercial Power Frequencies
This standard is issued under the fixed designation D2477; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method covers the determination of the dielec- 2.1 ASTM Standards:
tric breakdown voltage and dielectric strength of insulating D2864 Terminology Relating to Electrical Insulating Liq-
gases used in transformers, circuit breakers, cables, and similar uids and Gases
apparatus as an insulating medium. The test method is appli-
2.2 IEEE Standard:
cableonlytogaseswithboilingpointsbelowroomtemperature
No. 4 Standard Techniques for High Voltage Testing
at atmospheric pressure.
2.3 ASTM Adjuncts:
Dielectric cell assembly and detail (2 drawings)
1.2 This standard may involve hazardous materials,
operations, and equipment. This standard does not purport to
3. Terminology
address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to 3.1 Definitions:
establish appropriate safety, health, and environmental prac-
3.1.1 For definitions of terms used in this test method, refer
tices and determine the applicability of regulatory limitations to Terminology D2864.
prior to use.
4. Significance and Use
1.3 Mercury has been designated by EPA and many state
agencies as a hazardous material that can cause central
4.1 The dielectric breakdown voltage and dielectric strength
nervous system, kidney and liver damage. Mercury, or its
of an insulating gas in a uniform field depends primarily on the
vapor, may be hazardous to health and corrosive to materials.
molecular structure of the gas. As different gases are mixed
Caution should be taken when handling mercury and mercury
either by plan or by contamination, any change in dielectric
containing products. See the applicable product Material
breakdown voltage and dielectric strength will depend on both
Safety Data Sheet (MSDS) for details and EPA’s website —
the nature and proportion of the individual gases. This test
http://www.epa.gov/mercury/faq.htm for additional informa-
method uses plane and spherical electrodes which provide a
tion. Users should be aware that selling mercury and/or
nearly uniform field (see Appendix) in the area of electrical
mercury containing products into your state may be prohibited
discharge. It is suitable for determining the dielectric break-
by state law.
down voltage and dielectric strength of different gases and
1.4 This international standard was developed in accor-
mixtures thereof for research and application evaluations and
dance with internationally recognized principles on standard-
also as a field test. A more complete discussion of the
ization established in the Decision on Principles for the
significance of the dielectric strength test is given in the
Development of International Standards, Guides and Recom-
Appendix.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This test method is under the jurisdiction of ASTM Committee D27 on Standards volume information, refer to the standard’s Document Summary page on
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom- the ASTM website.
mittee D27.05 on Electrical Test. Available from The Institute of Electrical and Electronic Engineers, Inc.
Current edition approved Nov. 1, 2020. Published November 2020. Originally (IEEE), 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331.
approved in 1966. Last previous edition approved in 2012 as D2477 – 07(2012). Detaileddrawingsofthisapparatusareavailableatanominalcostfrom:ASTM
DOI: 10.1520/D2477-07R20. International Headquarters. Order Adjunct No. ADJD2477-E-PDF.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2477 − 07 (2020)
5. Apparatus 5.2.1 Vacuum Pump— The vacuum pump shall have suffi-
cient pumping capacity to be able to evacuate the test cell to a
5.1 Electrical Apparatus:
pressure below 0.133 kPa (1 torr).
5.1.1 Transformer— The desired test voltage may be most
5.2.2 Vacuum and Pressure Gage—Either a mercury
readily obtained by a step-up transformer energized from a
manometer, or one or more gages, capable of measuring
variable low-voltage commercial power frequency source. The
pressures below 0.133 kPa (1 torr) and also near atmospheric
transformer and controlling element shall be of such size and
pressure. The manometer, or vacuum and pressure gages, shall
designthat,withthetestspecimeninthecircuit,thecrestfactor
be calibrated in kPa or millimetres of mercury (torr).
(ratio of maximum to mean effective) of the 60-Hz test voltage
5.2.3 Connections— Vacuum-tight tubing and valves shall
does not differ by more than 65 % from that of a sinusoidal
be used while evacuating and purging the test cell and filling it
wave over the upper half of the range of test voltage. The crest
with the gas sample.
factor may be checked by means of an oscilloscope, a sphere
5.3 Electrodes and Test Cell:
gap, or a peak-reading voltmeter in conjunction with an rms
5.3.1 The sphere and plane electrodes shall be mounted
voltmeter. Where the waveform cannot be determined
vertically as shown in Fig. 1. The sphere shall be a precision
conveniently, a transformer having a rating of not less than ⁄2
steel bearing ball 19.1 mm (0.75 in.) in diameter. The plane
kVAat the usual breakdown voltage shall be used. Transform-
electrode shall be of brass 38.1 mm (1.50 in.) in diameter. The
ers of larger kVA capacity may be used, but in no case should
gap setting shall be 2.54 6 0.025 mm (0.100 6 0.001 in.). The
the power frequency short circuit current in the specimen
tolerance of all dimensions is 62 %, unless otherwise stated.
circuit be outside the range of 1 to 10 mA/kV of applied
5.3.2 The cell shall consist of a borosilicate glass cylinder
voltage. This limitation of current may be accomplished by
clamped by flanges to end plates which seal the cell and
using a suitable external series resistor or by employing a
support the electrodes. The lower plane electrode shall be
transformer with sufficient inherent reactance.
fixed. The sphere electrode, held in place by a magnet, shall be
5.1.2 Circuit-Interrupting Equipment —Thetesttransformer
adjustable by means of a micrometer screw suitably mounted
primary circuit shall be protected by an automatic circuit-
through the top plate. The micrometer screw must be suitable
breaking device capable of opening (as nearly instantaneously
for setting the electrodes to within the specified tolerance. The
as possible) on the current produced by the breakdown of the
bottom plate shall have a valved port for evacuation and
test specimen; a circuit breaker that opens within 5 cycles may
admission of the sample. If considered more convenient, two
be used if the short-circuit current as described in 5.1.1 does
ports, one in the top for evacuation and one in the bottom for
not exceed 200 mA.Aprolonged flow of current at the time of
admission of the sample may be used. The dimensions are
breakdown causes contamination of the gases and damage of
shown in Fig. 1.
theelectrodes,therebyaffectingthesubsequenttestresults,and
increasing the electrode and test cell maintenance and time of
6. Sampling
testing.
6.1 Obtainthegassamplefromthegascylinderorgas-filled
5.1.3 Voltage-Control Equipment—The rate of voltage rise
1 equipment through a pressure-reducing regulator valve so that
shall be ⁄2 kV/s 6 20 %. Voltage control may be secured by a
the flow into the cell may be controlled. The sample and cell
motor-driven variable-ratio-autotransformer. Preference is
must be at room temperature before the gas is admitted to the
given to equipment having an approximately straight-line
cell.
voltage-time curve over the desired operating range. Motor
drive is preferred to manual drive because of the ease of
7. Preparation of Cell
maintaining a reasonably uniform rate-of-voltage rise with this
7.1 Clean the cell except for the electrodes by washing with
test method. The rate-of-voltage rise may be calculated from
soap or detergent, then rinse with distilled or demineralized
measurements of the time required to raise the voltage between
water and oven-dry. Clean the cell whenever necessary to
two prescribed values. When motor-driven equipment is used,
remove detectable decomposition products formed by the
calibrate the speed control rheostat in terms of rate-of-voltage
breakdown arc, or when testing different gases.
rise for the test transformer used.
5.1.4 Voltmeter—Measure the voltage by a method that
7.2 Clean the electrodes with crocus cloth and naphtha.
fulfills the requirements of IEEE Standard No. 4, giving crest
When the sphere electrode becomes pitted, it may be turned to
and a
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