ASTM D3756-18
(Test Method)Standard Test Method for Evaluation of Resistance to Electrical Breakdown by Treeing in Solid Dielectric Materials Using Diverging Fields
Standard Test Method for Evaluation of Resistance to Electrical Breakdown by Treeing in Solid Dielectric Materials Using Diverging Fields
SIGNIFICANCE AND USE
5.1 This is a laboratory test designed to simulate the effects of (1) the presence of rough interfaces between conductor or semiconductive screen and primary insulation in an insulation system, (2) the presence of foreign particles (contaminants) in an insulation system, and (3) the presence of small voids or cavities within the insulation.
5.2 This test method provides comparative data. The degree of correlation with actual performance in service has not been established.
SCOPE
1.1 This test method covers the evaluation and comparison of the resistance of solid organic dielectric materials to the initiation or growth, or both, of tubular tree-like channels resulting from partial discharge (corona) and molecular decomposition that occur in the region of very high, diverging electric fields.3,4
1.2 This test method is primarily for use at a power frequency of 50 or 60 Hz.
1.3 The test is able to be carried out at room temperature or temperatures above or below room temperature. The temperature shall not exceed the softening or melting point of the sample material.
1.4 This test method can be used for any solid material into which needles can be cast, molded, or inserted with heat after molding. The resistance to tree initiation is measured by the double-needle characteristic voltage, which is only applicable to non-opaque materials so that tree can be observed optically. The resistance to tree initiation and growth is reported by the double-needle voltage life, which is applicable to both opaque and non-opaque materials.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 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.
1.7 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.
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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: D3756 − 18
Standard Test Method for
Evaluation of Resistance to Electrical Breakdown by Treeing
1
in Solid Dielectric Materials Using Diverging Fields
This standard is issued under the fixed designation D3756; 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.
INTRODUCTION
When failure occurs in solid organic dielectrics that are subjected to very high, continuous, and
nonuniform electrical gradients, it generally occurs by a mechanism called treeing. Materials of
different molecular structures have different degrees of resistance to failure by treeing, and this
2
resistance can sometimes be increased by the addition of other materials in low concentration.
Treesthatgrowbyamoleculardegradationmechanismresultingfrompartialdischarge(corona)are
called electrical trees to distinguish them from water and electrochemical trees which are quite
different.
This test method makes use of two opposing thin cylindrical electrodes, one sharpened to a point,
the other with a hemispherical end. They are molded or inserted into blocks of the material to be
tested. Because of the shape of the electrodes this is often called a needle test. This test provides a
statistical estimate of electrical treeing initiation and propagation of solid dielectric materials in high,
diverging electrical fields.
1. Scope 1.3 The test is able to be carried out at room temperature or
temperatures above or below room temperature. The tempera-
1.1 This test method covers the evaluation and comparison
ture shall not exceed the softening or melting point of the
of the resistance of solid organic dielectric materials to the
sample material.
initiation or growth, or both, of tubular tree-like channels
resultingfrompartialdischarge(corona)andmoleculardecom-
1.4 This test method can be used for any solid material into
positionthatoccurintheregionofveryhigh,divergingelectric
which needles can be cast, molded, or inserted with heat after
3,4
fields.
molding. The resistance to tree initiation is measured by the
double-needle characteristic voltage, which is only applicable
1.2 This test method is primarily for use at a power
to non-opaque materials so that tree can be observed optically.
frequency of 50 or 60 Hz.
The resistance to tree initiation and growth is reported by the
double-needle voltage life, which is applicable to both opaque
1
This test method is under the jurisdiction of ASTM Committee D09 on
and non-opaque materials.
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.12 on Electrical Tests.
1.5 The values stated in SI units are to be regarded as the
Current edition approved Nov. 1, 2018. Published November 2018. Originally
approved in 1990. Last previous edition approved in 2010 as D3756–97(2010). standard.
DOI: 10.1520/D3756-18.
2
1.6 This standard does not purport to address all of the
Symposium on Engineering Dielectrics, ASTM STP 783, ASTM, 1982, and
Symposium on Engineering Dielectrics, ASTM STP 926, ASTM, 1986.
safety concerns, if any, associated with its use. It is the
3
W. D.Wilkens, Chapter 7, “Statistical Methods for the Evaluation of Electrical
responsibility of the user of this standard to establish appro-
InsulatingSystems,” Engineering Dielectrics, Vol IIB, Electrical Properties of Solid
priate safety, health, and environmental practices and deter-
Insulating Materials, Measurement Techniques, R. Bartnikas, Editor, ASTM STP
mine the applicability of regulatory limitations prior to use.
926, ASTM, Philadelphia, 1987.
4
R. M. Eichorn, Chapter 4, “Treeing in Solid Organic Dielectric Materials,”
1.7 This international standard was developed in accor-
Engineering Dielectrics, Vol IIA, Electrical Properties of Solid Insulating Materi-
dance with internationally recognized principles on standard-
als: Molecular Structure and Electrical Behavior, R. Bartnikas and R. M. Eichorn,
Editors, ASTM STP 783, ASTM Philadelphia, 1983. ization established in the Decision on Principles for the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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D3756 − 18
Development of International Standards, Guides and Recom- 5.2 Thistestmethodprovidescomparativedata.Thedegree
mendations issued by the World Trade Organization Technical of correlation with actual performance in service has not been
Barriers to Trade (TBT) C
...
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: D3756 − 97 (Reapproved 2010) D3756 − 18
Standard Test Method for
Evaluation of Resistance to Electrical Breakdown by Treeing
1
in Solid Dielectric Materials Using Diverging Fields
This standard is issued under the fixed designation D3756; 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.
INTRODUCTION
When failure occurs in solid organic dielectrics that are subjected to very high, continuous, and
nonuniform electrical gradients, it generally occurs by a mechanism called treeing. Materials of
different molecular structures have different degrees of resistance to failure by treeing, and this
2
resistance can sometimes be increased by the addition of other materials in low concentration.
Trees that grow by a molecular degradation mechanism resulting from partial discharge (corona) are
called electrical trees to distinguish them from water and electrochemical trees which are quite
different.
This test method makes use of two opposing thin cylindrical electrodes, one sharpened to a point,
the other with a hemispherical end. They are molded or inserted into blocks of the material to be
tested. Because of the shape of the electrodes this is often called a needle test. This test provides a
statistical estimate of electrical treeing initiation and propagation of solid dielectric materials in high,
diverging electrical fields.
1. Scope
1.1 This test method covers the evaluation and comparison of the resistance of solid organic dielectric materials to the initiation
or growth, or both, of tubular tree-like channels resulting from partial discharge (corona) and molecular decomposition that occur
3,4
in the region of very high, diverging electric fields.
1.2 This test method is primarily for use at a power frequency of 50 or 60 Hz.
1.3 The test may is able to be carried out at room temperature or temperatures above or below room temperature. The
temperature shouldshall not exceed the softening or melting point of the sample material.
1.4 This test method can be used for any solid material into which needles can be cast, molded, or inserted with heat after
molding. The resistance to tree initiation is measured by the double-needle characteristic voltage, which is only applicable to
non-opaque materials so that tree can be observed optically. The resistance to tree initiation and growth is reported by the
double-needle voltage life, which is applicable to both opaque and non-opaque materials.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.7 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.
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 Oct. 1, 2010Nov. 1, 2018. Published October 2010November 2018. Originally approved in 1990. Last previous edition approved in 20042010
as D3756 – 97 (2010).(2004). DOI: 10.1520/D3756-97R10.10.1520/D3756-18.
2
Symposium on Engineering Dielectrics, ASTM STP 783, ASTM, 1982, and Symposium on Engineering Dielectrics, ASTM STP 926, ASTM, 1986.
3
W. D. Wilkens, Chapter 7, “Statistical Methods for the Evaluation of Electrical Insulating Systems,” Engineering Dielectrics, Vol IIB, Electrical Properties of Solid
Insulating Materials, Measurement Techniques, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987.
4
R. M. Eichorn, Chapter 4, “Treeing in Solid Organic Dielectric Materials,” Engineering Dielectrics, Vol IIA, Electrical Properties of Solid Insulating Materials:
Molecular Structure and Electrical Behavior, R. Bartnikas and R. M. Eichorn, Editors, ASTM STP 783, ASTM Philadelphia, 1983.
Copyright © ASTM International, 100 Barr
...
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