ASTM D5288-97(2004)

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An American National Standard
Designation:D5288–97 (Reapproved 2004)
Standard Test Method for
Determining the Tracking Index of Electrical Insulating
Materials Using Various Electrode Materials (Excluding
Platinum)
This standard is issued under the fixed designation D5288; 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 D1898 Practice for Sampling of Plastics
D3638 Test Method for Comparative Tracking Index of
1.1 Thistestmethodwasdevelopedusingcopperelectrodes
Electrical Insulating Materials
toevaluatethelow-voltage(upto600V)trackingresistanceof
2 2.2 IEC Publication:
materials in the presence of aqueous contaminants.
IEC 112, Recommended Method for Determining the Com-
NOTE 1—At this time, only industrial laminates have been examined
parative Track Index of Solid Insulating Materials Under
using this method which was developed at the National Manufacturers
Moist Conditions, 1971 Second Edition
Electrical Association (NEMA) laboratory located at the University of
Cincinnati. It was found that a closer end point (less scatter) was obtained
3. Terminology
thanwithplatinumelectrodes,andmaterialstestedtendedtoberankedby
3.1 In addition to the definitions listed below, terminology
resin system.
as defined in Terminology D1711 is assumed.
1.1.1 Other electrode materials may be considered for use
3.2 Definitions:
with this test method depending upon the application of the
3.2.1 track, n—a partially conducting path of localized
insulating material.
deterioration on the surface of an insulating material.
1.2 This test method is similar to Test Method D3638,
3.2.2 tracking, n—the process that produces tracks as a
which determines the comparative tracking index of materials
result of the action of electric discharges on or close to an
using platinum electrodes to produce the tracking on the
insulation surface.
specimen surface.
3.2.3 tracking, contamination, n—tracking caused by scin-
1.3 The values stated in metric (SI) units are the standard.
tillations that result from the increased surface conduction due
The inch-pound equivalents of the metric units are approxi-
to contamination.
mate.
3.2.4 tracking index, TI, n—an index for electrical insulat-
1.4 This standard does not purport to address all of the
ingmaterialswhichisarbitrarilydefinedasthenumericalvalue
safety concerns, if any, associated with its use. It is the
of that voltage which will cause failure by tracking when the
responsibility of the user of this standard to establish appro-
number of drops of contaminant required to cause failure is
priate safety and health practices and determine the applica-
equal to 50.
bility of regulatory limitations prior to use.
3.2.4.1 Discussion—This value is obtained from a plot of
the number of drops required to cause failure by tracking
2. Referenced Documents
versus the applied voltage.
2.1 ASTM Standards:
3.2.5 tracking index–copper electrodes, TI-Cu, n—a track-
D618 Practice for Conditioning Plastics for Testing
ing index test using copper electrodes.
D1711 Terminology Relating to Electrical Insulation
3.2.5.1 Discussion—This test is comparable to comparative
tracking index,Test Method D3638, with the following excep-
This test method is under the jurisdiction of ASTM Committee D09 on
tions: (1) copper electrodes are used instead of platinum, and
Electrical and Electronic Insulating Materials and is the direct responsibility of
(2) the electrodes may have to be re-ground after every test
Subcommittee D09.12 on Electrical Tests.
because of the softness of copper.
Current edition approved March 1, 2004. Published March 2004. Originally
3.2.6 tracking resistance, n—the quantitative expression of
approved in 1992. Last previous edition approved in 1997 as D5288–97. DOI:
10.1520/D5288-97R04.
the voltage and the time required to develop a track under
Mathes, K. N., Chapter 4, “Surface Failure Measurements,” Engineering
specified conditions.
Dielectrics, Vol IIB, Electrical Properties of Solid Insulating Materials, Measure-
ment Techniques, R. Bartnikas, Editor, ASTM STP 926,ASTM, Philadelphia, 1987.
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 Withdrawn.
Standards volume information, refer to the standard’s Document Summary page on Available from the International Electrotechnical Commission, Geneva, Swit-
the ASTM website. zerland.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5288–97 (2004)
4. Summary of Test Method
4.1 The surface of a specimen of electrical insulating
material is subjected to a low-voltage alternating stress com-
bined with a low current which results from an aqueous
contaminant (electrolyte) which is dropped between two op-
posingcopperelectrodesevery30s.Thevoltageappliedacross
these electrodes is maintained until the current flow between
them exceeds a predetermined value which constitutes failure.
Additional specimens are tested at other voltages so that a
relationship between applied voltage and number of drops to
failure can be established through graphical means. The
numerical value of the voltage which causes failure with the
application of 50 drops of the electrolyte is arbitrarily called
the tracking index. This value provides an indication of the
FIG. 1 Electrical Circuit Components
relative track resistance of the material.
platinum electrodes in the same type of test. It is a fact that
5. Significance and Use
copper is more widely used than platinum for electrical
5.1 Electrical equipment may fail as a result of electrical
conductors.
tracking of insulating material that is exposed to various
6. Apparatus
contaminating environments and surface conditions. There are
a number of ASTM and other tests designed to quantify
6.1 The simplified electrical circuitry used in this test is
behavior of materials, especially at relatively high voltages.
illustrated in Fig. 1. For necessary information on the cleanli-
This method is an accelerated test which at relatively low test
ness of apparatus, see Annex A1. The essential components
voltages, provides a comparison of the performance of insu-
are:
lating materials under wet and contaminated conditions. The
6.1.1 Variable Power Source, consisting of a transformer
Tracking Index—Copper Electrodes test is not related directly
type supply, such as the combinationT andT in Fig. 1, with
1 2
to the suitable operating voltage in service.
a variable output of 0 to 1000V, 60 Hz capable of maintaining
5.2 When organic electrical insulating materials are sub-
a current of 1 A (1 kVA).
jected to conduction currents between electrodes on their
6.1.2 Voltmeter (V ), capable of measuring the varying ac
surfaces, many minute tree-like carbonaceous paths or tracks
output of the power source. A0 to 600-V voltmeter with an
are developed near the electrodes. These tracks are oriented
accuracy of at least 60.5% of full scale.
randomly, but generally propagate between the electrodes
6.1.3 Ammeter (A ), with a range of 0 to 1 A ac and an
under the influence of the applied potential difference. Even-
accuracy of at least 610% of full scale.
tually a series of tracks spans the electrode gap, and failure
6.1.4 Current Limiting Resistor (R ), continuously vari-
occurs by shorting of the electrodes.
able, wire wound, rated at greater than 1 A.
5.3 As in other tracking test methods, for example, IEC 112
6.1.5 Shorting Switch (S ), single-pole single-throw rated
and Test Method D3638, this test method specifies test proce- at 1000 V and greater than 1 A.
dures that are intended to promote the formation of surface
NOTE 2—The need for a shorting switch is optional. It is possible to
discharges which will produce carbon tracks in a reproducible
couple the variable resistor with the autotransformer which gives an
manner. Since these conditions rarely reproduce the actual
automatic setting of the current throughout the range of the instrument.
conditions encountered in service, the results of tracking tests
Then whenever it is necessary to check the calibration of the instrument,
cannotbeusedtoinfereitherdirectorrelativeservicebehavior the shorting action can be accomplished by a jumper wire placed across
the electrodes. This coupling of the autotransformer with the variable
ofamaterialinaspecificdesignapplication.Trackingtestscan
resistor is another option.
be used for screening purposes only. Suitability is verified
through testing of the material in actual end use or under 6.1.6 Over-Current Relay (R ), shall not trip at currents up
conditions that closely simulate actual end use. to 0.1 A and the tripping time on short circuit shall be a
minimum of 0.5 s (the current shall be limited on short circuit
5.4 The use of copper electrodes in this type of test was
to 1 A with a tolerance of 610% at a power factor of 0.9 to
developedattheUniversityofCincinnati,NEMAlaboratory.It
is felt by the members of the Industrial Laminates Section of 1.0).
NEMA that using copper electrodes gives a more realistic
value for a tracking index, related to the resin system used to
Middendorf, W. H. and Vemuri, R., “Report on Copper vs. Platinum Elec-
reinforce the substrate of a laminate. In general, tracking tests
trodes,” 1990,Available from National Electrical Manufacturer’sAssociation, 2101
made with copper electrodes tend to give lower values than L St. N.W., Suite 300, Washington, D.C. 20037-8400.
D5288–97 (2004)
until these limits are observed.Adjustment is accomplished by
adding water or NH Cl.
7.1.3 Calibrate the conductivity cell with 0.01 N potassium
chloride calibrating solution which is available from the cell
manufacturer.
8. Test Specimens
8.1 Samples should be selected in accordance with Practice
D1898.
8.2 Typical test specimens are 50 mm (2 in.) or 100 mm (4
in.) diameter disks or any other similar shape. The minimum
thickness is 2.5 mm (0.100 in.). Test five specimens of each
sample.
8.3 Variations in values can result from a lack of uniformity
of dispersion of the material throughout the molded specimen
FIG. 2 Electrodes (Radius 0.05 to 0.1 mm)
or from surface imperfectio
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