ASTM D495-22

Standard Test Method for High-Voltage, Low-Current, Dry Arc Resistance of Solid Electrical Insulation

SIGNIFICANCE AND USE
4.1 The high-voltage, low-current type of arc resistance test is intended to simulate only approximately such service
conditions as exist in alternating current circuits operating at high voltage, but at currents limited to units and tens of milliamperes.  
4.2 In order to distinguish more easily among materials that have low arc resistance, the early stages of this test method are mild, and the later stages are successively more severe. The arc occurs intermittently between two electrodes resting on the surface of the specimen, in normal or inverted orientation. The severity is increased in the early stages by successively decreasing to zero the interval between flashes of uniform duration, and in later stages by increasing the current.  
4.3 Four general types of failure have been observed:  
4.3.1 Many inorganic dielectrics become incandescent, whereupon they are capable of conducting the current. Upon cooling, however, they return to their earlier insulating condition.  
4.3.2 Some organic compounds burst into flame without the formation of a visible conducting path in the substance.  
4.3.3 Others are seen to fail by “tracking,” that is, a thin wiry line is formed between the electrodes.  
4.3.4 The fourth type occurs by carbonization of the surface until sufficient carbon is present to carry the current.  
4.4 Materials often fail within the first few seconds after a change in the severity stage. When comparing the arc resistance of materials, much more weight shall be given to a few seconds that overlap two stages than to the same elapsed time within a stage. Thus, there is a much greater difference in arc resistance between 178 and 182 s than between 174 and 178 s.
Note 4: Some investigators have reported attempts to characterize the remaining insulating value of the damaged area after failure by allowing the specimen to cool to room temperature, without disturbance of the original position of the electrodes, and then either (1) measuring the insu...
SCOPE
1.1 This test method covers, in a preliminary fashion, the differentiation of similar materials’ resistance to the action of a high-voltage, low-current arc close to the surface of insulation, when a conducting path is formed causing the material to become conducting due to the localized thermal and chemical decomposition and erosion.  
1.2 The usefulness of this test method is very severely limited by many restrictions and qualifications, some of which are described in the following paragraphs and in Section 5. Generally, this test method shall not be used in material specifications. Whenever possible, alternative test methods shall be used, and their development is encouraged.  
1.3 This test method will not, in general, permit conclusions to be drawn concerning the relative arc resistance rankings of materials that are potentially subjected to other types of arcs: for example, high voltage at high currents, and low voltage at low or high currents (promoted by surges or by conducting contaminants).  
1.4 The test method is intended, because of its convenience and the short time required for testing, for preliminary screening of material, for detecting the effects of changes in formulation, and for quality control testing after correlation has been established with other types of simulated service arc tests and field experience. Because this test method is usually conducted under clean and dry laboratory conditions rarely encountered in practice, it is possible that the prediction of a material's relative performance in typical applications and in varying “clean to dirty” environments will be substantially altered (Note 1). Caution is urged against drawing strong conclusions without corroborating support of simulated service tests and field testing. Rather, this test method is useful for preliminary evaluation of changes in structure and composition without the complicating influence of environmental conditions, espe...

General Information

• Status: Published
• Publication Date: 14-Jan-2022
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.12 - Electrical Tests

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: D495 − 22
Standard Test Method for
High-Voltage, Low-Current, Dry Arc Resistance of Solid
1
Electrical Insulation
This standard is issued under the fixed designation D495; 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* without the complicating influence of environmental
conditions, especially dirt and moisture.
1.1 This test method covers, in a preliminary fashion, the
differentiation of similar materials’resistance to the action of a
NOTE 1—By changing some of the circuit conditions described herein
it has been found possible to rearrange markedly the order of arc
high-voltage,low-currentarcclosetothesurfaceofinsulation,
resistance of a group of organic insulating materials consisting of
when a conducting path is formed causing the material to
vulcanized fiber and of molded phenolic and amino plastics, some
become conducting due to the localized thermal and chemical
containing organic, and some inorganic, filler.
decomposition and erosion.
1.5 While this test method uses dry, uncontaminated speci-
1.2 The usefulness of this test method is very severely
men surfaces, Test Method D2132, Test Methods D2303, and
limited by many restrictions and qualifications, some of which
Test Method D3638 employ wet, contaminated specimen
are described in the following paragraphs and in Section 5.
surfaces. Their use is recommended for engineering purposes
Generally, this test method shall not be used in material
and to assist in establishing some degree of significance to this
2
specifications. Whenever possible, alternative test methods
test method for quality control purposes.
shall be used, and their development is encouraged.
1.6 This test method is not applicable to materials that do
1.3 Thistestmethodwillnot,ingeneral,permitconclusions
not produce conductive paths under the action of an electric
to be drawn concerning the relative arc resistance rankings of
arc, or that melt or form fluid residues that float conductive
materials that are potentially subjected to other types of arcs:
residues out of the active test area thereby preventing forma-
for example, high voltage at high currents, and low voltage at
tion of a conductive path.
low or high currents (promoted by surges or by conducting
1.7 Thevaluesstatedininch-poundunitsaretoberegarded
contaminants).
as standard. The values given in parentheses are mathematical
1.4 The test method is intended, because of its convenience
conversions to SI units that are provided for information only
and the short time required for testing, for preliminary screen-
and are not considered standard.
ing of material, for detecting the effects of changes in
1.8 This standard does not purport to address all of the
formulation,andforqualitycontroltestingaftercorrelationhas
safety concerns, if any, associated with its use. It is the
been established with other types of simulated service arc tests
responsibility of the user of this standard to establish appro-
and field experience. Because this test method is usually
priate safety, health, and environmental practices and deter-
conducted under clean and dry laboratory conditions rarely
mine the applicability of regulatory limitations prior to use.
encountered in practice, it is possible that the prediction of a
For specific precautionary statements, see 6.1.14, 6.1.19, Sec-
material’s relative performance in typical applications and in
tion 7, and 10.1.1.
varying “clean to dirty” environments will be substantially
altered (Note 1). Caution is urged against drawing strong NOTE 2—Due to the deficiencies covered in Section 1, Committee D09
has proposed that without significant proposed improvements this stan-
conclusionswithoutcorroboratingsupportofsimulatedservice
dard be withdrawn in 2027 during its next 5 year review. This notice is
tests and field testing. Rather, this test method is useful for
provided so that referencing standards can transition.
preliminaryevaluationofchangesinstructureandcomposition
1.9 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
1
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
2
Subcommittee D09.12 on Electrical Tests. Also helpful i
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D495 − 14 D495 − 22
Standard Test Method for
High-Voltage, Low-Current, Dry Arc Resistance of Solid
1
Electrical Insulation
This standard is issued under the fixed designation D495; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 This test method covers, in a preliminary fashion, the differentiation of similar materials’ resistance to the action of a
high-voltage, low-current arc close to the surface of insulation, when a conducting path is formed causing the material to become
conducting due to the localized thermal and chemical decomposition and erosion.
1.2 The usefulness of this test method is very severely limited by many restrictions and qualifications, some of which are described
in the following paragraphs and in Section 5. Generally, this test method shall not be used in material specifications. Whenever
possible, alternative test methods shall be used, and their development is encouraged.
1.3 This test method will not, in general, permit conclusions to be drawn concerning the relative arc resistance rankings of
materials that are potentially subjected to other types of arcs: for example, high voltage at high currents, and low voltage at low
or high currents (promoted by surges or by conducting contaminants).
1.4 The test method is intended, because of its convenience and the short time required for testing, for preliminary screening of
material, for detecting the effects of changes in formulation, and for quality control testing after correlation has been established
with other types of simulated service arc tests and field experience. Because this test method is usually conducted under clean and
dry laboratory conditions rarely encountered in practice, it is possible that the prediction of a material’s relative performance in
typical applications and in varying “clean to dirty” environments will be substantially altered (Note 1). Caution is urged against
drawing strong conclusions without corroborating support of simulated service tests and field testing. Rather, this test method is
useful for preliminary evaluation of changes in structure and composition without the complicating influence of environmental
conditions, especially dirt and moisture.
NOTE 1—By changing some of the circuit conditions described herein it has been found possible to rearrange markedly the order of arc resistance of a
group of organic insulating materials consisting of vulcanized fiber and of molded phenolic and amino plastics, some containing organic, and some
inorganic, filler.
1.5 While this test method uses dry, uncontaminated specimen surfaces, Test Method D2132, Test Methods D2303, and Test
Method D3638 employ wet, contaminated specimen surfaces. Their use is recommended for engineering purposes and to assist in
2
establishing some degree of significance to this test method for quality control purposes.
1
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.12 on Electrical Tests.
Current edition approved April 1, 2014Jan. 15, 2022. Published May 2014January 2022. Originally approved in 1938. Last previous edition approved in 20042014 as
D495 – 94 (2004)D495, which was withdrawn in January 2013 and reinstated in April 2014. DOI: 10.1520/D0495-14. – 14. DOI: 10.1520/D0495-22.
2
Also helpful is Test Method D2302 for Wet Tracking Resistance of Electrical Insulating Materials with Controlled Water-to-Metal Discharges. This test method was
withdrawn and last appeared in the 1982 Annual Book of ASTM Standards, Part 39.
*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
1

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D495 − 22
1.6 This test method is not applicable to materials that do not produce conductive paths under the action of an electric arc, or that
melt or form fluid residues that float conductive residues out of the active test area thereby preventing formation of a conductive
path.
1.7 The values stated in inch-pound units are to be regarded as standard. The values g
...