Method—Electrical insulation in service can fail as a result of tracking, erosion, or a combination of both, if exposed to high relative humidity and contamination environments. This is particularly true of organic insulations in outdoor applications where the surface of the insulation becomes contaminated by deposits of moisture and dirt, for example, coal dust or salt spray. This test method is an accelerated test that simulates extremely severe outdoor contamination. It is believed that the most severe conditions likely to be encountered in outdoor service in the United States will be relatively mild compared to the conditions specified in this test method.

Test Results—Materials can be classified by this test method as tracking-resistant, tracking-affected, or tracking-susceptible. The exact test values for these categories as they apply to specific uses will be specified in the appropriate material specifications, but guideline figures are suggested in Note 3. Tracking-resistant materials, unless erosion failure occurs first, can last many hundreds of hours (Note 4). Erosion, though it can progress laterally, generally results in a failure perpendicular to the specimen surface. Therefore, only specimens of the same nominal thickness can be compared for resistance to tracking-induced erosion. The extent of erosion can be estimated from measurements of the depth of penetration of the erosion. Materials that are not tracking-susceptible can be placed in three broad categorieserosion-resistant, erosion-affected, and erosion-susceptible. When the standard thickness specimen is tested, the following times to failure typify the categories (Note 5):

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1.1 This test method is intended to differentiate solid electrical insulating materials with respect to their resistance to the action of electric arcs produced by conduction through surface films of a specified contaminant containing moisture. Test Methods and D2303 may also be used to evaluate materials.

1.2 The values stated in inch-pound units are the standard, except in cases where SI units are more appropriate. The values in parentheses are for information only.

1.3 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 and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in 12.4.

Note 1—There is no equivalent ISO standard.