The intent of the Arc Resistance test is to make a relative distinction between solid electrical insulating materials. The ability of the test specimens to resist an arc at a high voltage but with a weak current in the vicinity of the insulating surface is investigated. The test focuses on the time until tracking paths start to form.
Arc resistance, in accordance with ASTM-D495, is expressed as the number of seconds that a material resists the formation of a surface-conducting path when subjected to an intermittently occurring arc of high voltage, low current characteristics. The results of testing the nominal 3 mm thickness are considered representative of the material's performance in any thickness.
This test method covers, in a preliminary fashion, the differentiation among similar materials with respect to their resistance to the action of a high-voltage, low-current arc close to the surface of insulation, intending to form a conducting path therein or in causing the material to become conducting due to the localized thermal and chemical decomposition and erosion.
While this test method uses dry, uncontaminated specimen surfaces, Test Method ASTM D 2132, D 2303, and D 3638 employ wet, contaminated specimen surfaces. Their use is recommended for engineering purposes and to assist in establishing some degree of significance to this test method for quality control purposes.
This test method is not applicable to materials that do not produce conductive paths under the action of an electric arc, or that melt or form fluid residues that float conductive residues out of the active test area thereby preventing formation of a conductive path.