ASTM D3638-12

Standard Test Method for Comparative Tracking Index of Electrical Insulating Materials

SIGNIFICANCE AND USE
Electrical equipment can fail as a result of electrical tracking of insulating material that is exposed to various contaminating environments and surface conditions. There are a number of ASTM and other tests designed to quantify behavior of materials, especially at relatively high voltages. This method is an accelerated test which at relatively low test voltages, provides a comparison of the performance of insulating materials under wet and contaminated conditions. The comparative tracking index is not related directly to the suitable operating voltage in service.
When organic electrical insulating materials are subjected to conduction currents between electrodes on their surfaces, many minute tree-like carbonaceous paths or tracks are developed near the electrodes. These tracks are oriented randomly, but generally propagate between the electrodes under the influence of the applied potential difference. Eventually a series of tracks spans the electrode gap, and failure occurs by shorting of the electrodes.  
The conditions specified herein are intended, as in other tracking test methods, to produce a condition conducive to the formation of surface discharges and possible subsequent tracking. Test conditions are chosen to reproducibly and conveniently accelerate a process; for this reason, they rarely reproduce the varied conditions found in actual service. Therefore, while tracking tests serve to differentiate materials under given conditions, results of tracking tests cannot be used to infer either direct or comparative service behavior of an application design. Rather, tracking test results provide a tool for judging the suitability of materials for a given application. The suitability can only be verified through testing the design in actual end use or under conditions which simulate end use as closely as possible.
SCOPE
1.1 This test method evaluates in a short period of time the low-voltage (up to 600 V) track resistance or comparative tracking index (CTI) of materials in the presence of aqueous contaminants.
1.2 The values stated in metric (SI) units are to be regarded as standard. The inch-pound equivalents of the metric units are approximate.
1.3 This standard is technically equivalent to the version of IEC Publication 112 cited in 2.2. However, the 2007 version of IEC 60112 Fourth Edition yields numerical CTI values that are very likely to differ significantly from this standard.
1.4 This standard does not purport to address all of the safety problems, 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.

General Information

• Status: Historical
• Publication Date: 31-Dec-2011
• 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)

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: D3638 − 12
Standard Test Method for
Comparative Tracking Index of Electrical Insulating
1
Materials
This standard is issued under the fixed designation D3638; 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.
4
1. Scope* Moist Conditions, 2007 Fourth Edition
1.1 This test method evaluates in a short period of time the
3. Terminology
low-voltage (up to 600 V) track resistance or comparative
tracking index (CTI) of materials in the presence of aqueous 3.1 Definitions:
3.1.1 track—a partially conducting path of localized dete-
contaminants.
rioration on the surface of an insulating material.
1.2 The values stated in metric (SI) units are to be regarded
3.1.2 tracking—the process that produces tracks as a result
asstandard.Theinch-poundequivalentsofthemetricunitsare
of the action of electric discharges on or close to an insulation
approximate.
surface.
1.3 This standard is technically equivalent to the version of
3.1.3 tracking, contamination—trackingcausedbyscintilla-
IECPublication112citedin2.2.However,the2007versionof
tions that result from the increased surface conduction due to
IEC60112FourthEditionyieldsnumericalCTIvaluesthatare
contamination.
very likely to differ significantly from this standard.
3.1.4 tracking resistance—thequantitativeexpressionofthe
1.4 This standard does not purport to address all of the
voltage and the time required to develop a track under the
safety problems, if any, associated with its use. It is the
specified conditions.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3.1.5 For other terminology, refer to Terminology D1711.
bility of regulatory limitations prior to use.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 comparative tracking index—an index for electrical
2. Referenced Documents
insulating materials which is arbitrarily defined as the numeri-
2
2.1 ASTM Standards: cal value of that voltage which will cause failure by tracking
D1711Terminology Relating to Electrical Insulation
when the number of drops of contaminant required to cause
D6054Practice for Conditioning Electrical Insulating Mate- failure is equal to 50.
3
rials for Testing (Withdrawn 2012)
3.2.1.1 Discussion—The voltage value is obtained from a
2.2 IEC Publication: plot of the number of drops required to cause failure by
112Recommended Method for Determining the Compara- tracking versus the applied voltage.
tive Track Index of Solid Insulating Materials Under
3.2.2 failure, n—an attribute of an electrical circuit contain-
4
Moist Conditions, 1971 Second Edition
ing an electrical-current-sensing device that rapidly decreases
60112Recommended Method for Determining the Com-
the applied voltage to zero if the current in the circuit exceeds
parative Track Index of Solid Insulating Materials Under
a predetermined limit.
1 4. Summary of Test Method
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
4.1 The surface of a specimen of electrical insulating
Subcommittee D09.12 on Electrical Tests.
material is subjected to a low-voltage alternating stress com-
Current edition approved Jan. 1, 2012. Published February 2012. Originally
approved in 1977. Last previous edition approved in 2007 as D3638–07. DOI:
bined with a low current which results from an aqueous
10.1520/D3638-12.
contaminant (electrolyte) which is dropped between two op-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
posing electrodes every 30 s. The voltage applied across these
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
electrodes is maintained until the current between them ex-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
ceeds a predetermined value. This condition constitutes a
3
The last approved version of this historical standard is referenced on
failure. Additional specimens are tested at other voltages so
www.astm.org.
4
that a relationship between applied voltage and number of
Available from the International Electrotechnical Commission, Geneva, Swit-
zerland. drops to failure can be established through graphical means.
*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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D3638 − 12
The numerical value of the voltage which causes failure with 6.1.1 Vari
...

This document is not anASTM standard and is intended only to provide the user of anASTM 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.
An American National Standard
Designation:D3638–07 Designation: D3638 – 12
Standard Test Method for
Comparative Tracking Index of Electrical Insulating
1
Materials
This standard is issued under the fixed designation D3638; 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.
1. Scope*
1.1 This test method evaluates in a short period of time the low-voltage (up to 600 V) track resistance or comparative tracking
index (CTI) of materials in the presence of aqueous contaminants.
1.2 The values stated in metric (SI) units are to be regarded as standard. The inch-pound equivalents of the metric units are
approximate.
1.3 ThisstandardistechnicallyequivalenttotheversionofIECPublication112citedin2.2.However,the2007versionofIEC
60112 Fourth Edition yields numerical CTI values that are very likely to differ significantly from this standard.
1.4 This standard does not purport to address all of the safety problems, 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D1711 Terminology Relating to Electrical Insulation
D6054 Practice for Conditioning Electrical Insulating Materials for Testing
2.2 IEC Publication:
112 Recommended Method for Determining the Comparative Track Index of Solid Insulating Materials Under Moist
3
Conditions, 1971 Second Edition
60112 Recommended Method for Determining the Comparative Track Index of Solid Insulating Materials Under Moist
3
Conditions, 2007 Fourth Edition
3. Terminology
3.1 Definitions:
3.1.1 track—a partially conducting path of localized deterioration on the surface of an insulating material.
3.1.2 tracking—the process that produces tracks as a result of the action of electric discharges on or close to an insulation
surface.
3.1.3 tracking, contamination—tracking caused by scintillations that result from the increased surface conduction due to
contamination.
3.1.4 tracking resistance—thequantitativeexpressionofthevoltageandthetimerequiredtodevelopatrackunderthespecified
conditions.
3.1.5 For other terminology, refer to Terminology D1711.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 comparative tracking index—anindexforelectricalinsulatingmaterialswhichisarbitrarilydefinedasthenumericalvalue
of that voltage which will cause failure by tracking when the number of drops of contaminant required to cause failure is equal
to 50.
3.2.1.1 Discussion—The voltage value is obtained from a plot of the number of drops required to cause failure by tracking
versus the applied voltage.
3.2.2 failure, n—an attribute of an electrical circuit containing an electrical-current-sensing device that rapidly decreases 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 Subcommittee
D09.12 on Electrical Tests.
Current edition approved JuneJan. 1, 2007.2012. Published July 2007.February 2012. Originally approved in 1977. Last previous edition approved in 19982007 as
D3638–93(1998).D3638–07. DOI: 10.1520/D3638-07.10.1520/D3638-12.
2
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,[e-mail] Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
Available from the International Electrotechnical Commission, Geneva, Switzerland.
*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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D3638 – 12
applied voltage to zero if the current in the circuit exceeds a predetermined limit.
4. Summary of Test Method
4.1 The surface of a specimen of electrical insulating material is subjected to a low-voltage alternating stress combined with
a low current which results from an aqueous contaminant (electrolyte) which is dropped between two opposing electrodes every
30s.Thevoltageappliedacrosstheseelectrodesismaintaineduntilthecurrentbetweenthemexceedsapredeterminedvalue.This
conditionconstitutesafailure.Additionalspecimensaretestedatothervolt
...