ASTM D2303-97

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An American National Standard
Designation: D 2303 – 97
Standard Test Methods for
Liquid-Contaminant, Inclined-Plane Tracking and Erosion of
Insulating Materials
This standard is issued under the fixed designation D 2303; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope D 2132 Test Method for Dust- and Fog-Tracking and Ero-
sion Resistance of Electrical Insulating Materials
1.1 These test methods cover the evaluation of the relative
D 3638 Test Method for Comparative Tracking Index of
tracking and erosion resistance of insulating solids using the
2 Electrical Insulating Materials
liquid-contaminant, inclined-plane test. The following test
methods also can be used to evaluate the tracking resistance of
3. Terminology
materials: D 2132 (contaminants: dust and fog) and D 3638
3.1 Definitions:
(contaminant: conductive liquid drops).
3.1.1 erosion, electrical, n—the progressive wearing away
1.2 Two tracking and one erosion test procedure are de-
of electrical insulation by the action of electrical discharges.
scribed:
3.1.2 erosion resistance, electrical, n— the quantitative
1.2.1 A “variable voltage method” to evaluate resistance to
expression of the amount of electrical erosion under specific
tracking.
conditions.
1.2.2 A “time-to-track method” to evaluate resistance to
3.1.3 track, n—a partially conducting path of localized
tracking.
deterioration on the surface of an insulating material.
1.2.3 A method for quantitative determination of erosion
3.1.4 tracking, n—the process that produces tracks as a
(Annex A1).
result of the action of electric discharges on or close to the
1.3 While a particular contaminant solution is specified,
insulation surface.
other concentrations of the same contaminant, or different
3.1.5 tracking, contamination, n—tracking caused by scin-
contaminants may be used to simulate different environmental
tillations that result from the increased surface conduction due
or service conditions.
to contamination.
1.4 The values stated in inch-pound units are to be regarded
3.1.6 tracking resistance, n—the quantitative expression of
as the standard.
the voltage and the time required to develop a track under
1.5 This standard does not purport to address all of the
specified conditions.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 initial tracking voltage, n—the applied voltage at
priate safety and health practices and determine the applica-
which continuous tracking can be initiated in a specified time.
bility of regulatory limitations prior to use. Specific precau-
3.2.2 time-to-track, n—the time in which tracking proceeds
tionary statements are given in Section 8.
a specified distance between the test electrodes at a specified
2. Referenced Documents voltage.
3.3 Other definitions pertinent to these test methods are
2.1 ASTM Standards:
given in Terminology D 1711.
D 374 Test Methods for Thickness of Solid Electrical Insu-
lation
4. Significance and Use
D 1711 Terminology Relating to Electrical Insulation
4.1 These test methods differentiate among solid electrical
insulating materials on the basis of their resistance to the action
of voltage stresses along the surface of the solid when wet with
These test methods are under the jurisdiction of ASTM Committee D-9 on
Electrical and Electronic Insulating Materials and are the direct responsibility of
an ionizable, electrically conductive, liquid contaminant.
Subcommittee D09.12 on Electrical and Electronic Tests.
4.2 These test methods quantitatively evaluate, in a relative
Current edition approved Sept. 10, 1997. Published November 1997. Originally
manner, the effects upon an insulating material resulting from
issued as D 2303 – 64 T. Last previous edition D 2303 – 96.
K. N. Mathes, Chapter 4, “Surface Failure Measurements,” Engineering
Dielectrics, Vol IIB, Electrical Properties of Solid Insulating Materials, Measure-
ment Techniques, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987.
3 4
Annual Book of ASTM Standards, Vol 10.01. Annual Book of ASTM Standards, Vol 10.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 2303
the action of electrical discharges upon a material surface. The 4.4 The initial tracking voltage has been found useful for
effects are similar to those that may occur in service under the evaluating insulating materials to be used at high voltages or
influence of dirt combined with moisture condensed from the outdoors and unprotected, as well as for establishing (see 10.1)
atmosphere. the test voltage for the time-to-track test.
4.2.1 In the field, the conditions resulting in electrical
4.5 In service many types of contamination may cause
discharges occur sporadically. Degradation, often in the form
tracking and erosion of different materials to different degrees.
of a conducting “track”, develops very slowly until it ulti-
This method recognizes the importance of such variability and
mately bridges the space between conductors thus causing
suggests the use of special test solutions to meet specific
complete electrical breakdown.
service needs. For example, an ionic contaminant containing,
4.2.2 In these test methods, the conducting liquid contami-
in addition, a carbonaceous component such as sugar may be
nant is continuously supplied at an optimum rate to the surface
used to cause tracking on very resistant materials like polym-
of a test specimen in such a fashion that essentially continuous
ethylmethacrylate. Such contamination may be representative
electrical discharge can be maintained.
of some severe industrial environments. In this case, the
4.2.3 By producing continuous surface discharge with con-
time-to-track technique is used, since time is required to
trolled energy it is possible, within a few hours, to cause
decompose the contaminant solution and build up conducting
specimen failure which is similar to failure occurring under
residues on the sample surface.
long-time exposure to the erratic conditions of service in the
4.6 Very track-resistant materials, such as polymethyl-
field.
methacrylate, may erode rather than track under more usual
4.2.4 The test conditions, which are standardized and accel-
contaminant conditions in service. The use of this method for
erated, do not reproduce all of the conditions encountered in
measuring erosion is consequently important. For erosion
service. Use caution when making either direct or comparative
studies, only tests as a function of time at constant voltage are
service behavior inferences derived from the results of tracking
useful.
tests.
4.3 The time-to-track a 1-in. (25-mm) distance at a specified
5. Apparatus
voltage between electrodes separated 2 in. (50 mm) has also
been found useful in categorizing insulating materials for 5.1 A simple schematic diagram of the apparatus is given in
indoor and protected outdoor applications, such as metal-clad Fig. 1 and consists of the following. Details are given in Annex
switchgear. A2.
FIG. 1 Schematic Diagram of Apparatus
D 2303
5.1.1 A 60-Hz power supply with an output voltage stabi- 5.1.6 A 330-V, ⁄2-W, carbon resistor mounted with a
lized to 61 % which can be varied from 1 to at least 7.5 kV simple tension spring and connected in series with the speci-
with a rated current of no less than 0.1 A for every test station men and ground to act as an overload, high-voltage fuse.
to be used (that is, 0.5 A for five stations). 5.1.7 Structural parts and a grounded safety enclosure.
5.1.2 A means for applying a specified contaminant solution
6. Sampling
at a controlled rate to the specimen surface. A pneumatically
actuated repeating pipet has been found useful for this purpose 6.1 Refer to applicable materials specifications for sampling
instructions.
and is described in Annex A2. Peristaltic pumps have also been
used (A2).
7. Test Specimens
5.1.3 Stainless steel top and bottom electrodes as shown in
7.1 Make insulation specimens with a flat surface approxi-
Fig. 2.
FIG. 2 Top and Bottom Electrodes
NOTE 1—Stainless-steel type 302 is recommended.
mately 2 by 5 in. (50 by 130 mm) as shown in Fig. 4. Measure
the thickness in accordance with Test Methods D 374 if there
5.1.4 A pad of filter paper cut as shown in Fig. 3 to fit under
is no standard for a particular material. Specimens must be
the top electrode and used to smooth out the flow of the
thick enough that tracking does not penetrate completely
contaminant solution.
through the specimen during the test. Secure thin specimens to
5.1.5 A set of ballast resistors (50, 10, and 1-kV rated at 200
prevent sagging. Specimens thicker than ⁄4 in. (2 cm) are
W each) to be connected as specified in series with each test
difficult to clamp in the apparatus.
specimen on the high-voltage side of the power supply.
7.2 Prepare separate specimens exposing each surface of
Somewhat lower resistances are being considered by the
sheet or other materials with two or more surfaces which may
International Electrotechnical Commission (IEC/TC15).
have different characteristics. Carefully identify the surface so
International Resistance Co. RC 20-mil type carbon-composition resistors,
available from the TRW Electronics Corp., Commerce Terminal Bldg., Philadelphia,
PA, have been found satisfactory.
D 2303
FIG. 3 Filter Paper, Showing Clip and Method of Fastening
7.3 Preparation of Specimens—Clean the specimen face
with a suitable solvent and rinse with distilled water. For
specimens to be used in the time-to-track method, do not
mechanically destroy, that is, sand, abrade, etc. the natural
surface finish of the specimen unless otherwise specified.
However, with the variable-voltage method, the surface of the
test specimens should be lightly but completely sanded under
flowing tap water with 400A-grit wet silicon carbide paper and
rinsed with distilled water. Such sanding removes gloss and
contaminants to provide a surface that is wet more easily and
rapidly by the contaminant. Loss of gloss and slight erosion of
FIG. 4 Test Specimen
the surface usually occurs in service, particularly outdoors.
Generously cover the specimen area under the bottom elec-
trode with conductive silver paint and add the 1-in. (25-mm)
far as possible, that is, mold face, press face, etc. Prepare two
tracking reference marks as shown in Fig. 5. For all tests, other
sets of specimens of materials with noticeable directional
than the time-to-track test, soak the test specimens prepared as
characteristics, with the predominant directional characteristic
above for 24 to 48 h in the specified contaminant solution
in line with the electrodes for one set and at right angles to the
before test.
other set. Identify the specimen direction as far as possible; that
7.4 Prepare five specimens for each determination.
is, machine direction, cross-machine direction, warp or fill
direction (for woven textile reinforced products).Fig. 5
8. Procedure
8.1 Lethal voltages are a potential hazard during the
performance of this test. It is essential that the test apparatus,
and all associated equipment electrically connected to it, be
properly designed and installed for safe operation. Solidly
ground all electrically conductive parts which it is possible for
a person to contact during the test. Provide means for use at
the completion of any test to ground any parts which were at
high voltage during the test or have the potential for acquiring
an induced charge during the test or retaining a charge even
after disconnection of the voltage source. Thoroughly instruct
FIG. 5 Test Specimen Showing Location of Conducting Silver The solvent should not soften or otherwise damage the test specimen. Isopropyl
Paint and Tracking Reference Marks alcohol has been found suitable for many materials.
DuPont silver paint No. 4817 has been found suitable for this purpose.
D 2303
all operators as to the correct procedures for performing tests must have a resistivity between 370 and 400 V-cm when
safely. When making high voltage tests, particularly in com- measured at 23 6 1°C.
pressed gas or in oil, it is possible for the energy released at
8.4 Adjust the contaminant flow and calibrate as described
breakdown to be suffıcient to result in fire, explosion, or rupture in Annex A1 to give the flow rate for the voltage to be specified
of the test chamber. Design test equipment, test chambers, and
in Table 1.
test specimens so as to minimize the possibility of such
8.5 After calibration, the start-up procedure differs, depend-
occurrences and to eliminate the possibility of personal injury.
ing on whether the test specimen is a carry-over from a
If the potential for fire exists, have fire suppression equipment previous test, or an entirely new specimen.
available.
8.5.1 For a specimen that has never been subjected to
8.1.1 Also see Fig. 1.
voltages and contaminant (that is, new specimen), start the
contaminant injection into the filter paper, allowing the fresh
contaminant to wet the filter paper thoroughly and replace the
TABLE 1 Rates of Contaminant Application
old liquid in the tubes and syringes and to flow as a steady
NOTE 1—The rates of contaminant application shown are suitable only
stream (Note 2) (not intermittent bursts) across the test
for contaminants with a resistivity of approximately 370 to 400 V·cm at
specimen face between electrodes. The contaminant must flow
23°C on nonporous samples. With porous samples it may be nesessary to
from the quill hole in the bottom of the top electrode and
increase the contaminant flow somewhat to maintain effective, continual
scintillation. Lower contaminant resistivities also will require a higher rate should not squirt out of the sides or top of the filter paper
and higher resistivities, a lower rate of contaminant application; this must
during the pressure stroke of the pipet. Adjust the specimens so
be determined experimentally. At too high a contaminant rate scintillation
that the contaminant runs down as nearly as possible the center
will be greatly reduced because the current will flow in the contaminant
line of the specimen. Avoid drafts on equipment that might
film without disrupting it. At too low
...