Dry, Solid Insulating Materials - Resistance Test to High-Voltage, Low-Current Arc Discharges
|Publication Date:||1 September 1997|
|ICS Code (Insulating materials in general):||29.035.01|
|ICS Code (Other standards related to electricity and magnetism):||17.220.99|
This International Standard describes a test method which can provide preliminary differentiation between similar insulating materials, with respect to their resistance to damage when exposed to high-voltage, low-current arc discharges, occurring close to their surfaces.
The discharges cause localized thermal and chemical decomposition and erosion and eventually a conductive path forms across the insulating material. The severity of the test conditions is gradually increased: in the early stages a low-current arc discharge is repeatedly interrupted, whereas in the later stages, the arc current is raised in successive steps.
Because of its convenience and because of the short time required for testing, the test method is applicable for preliminary screening of materials, for detecting the effects of changes in formulation and for quality control testing.
Previous experience with this test, showed acceptable reproducibility with thermoset materials. Using thermoplastics, some testing laboratories report unacceptably large variation in test results which lead to the recommendation not to use the test for thermoplastics.
NOTE - Attempts are being made to reduce the variability of the results of tests on thermoplastics by controlling the electrode pressure and depth of penetration into the material during the test. Without such electrode control, tests on many thermoplastics may not be sufficiently meaningful to be performed.
This test method will not, in general, permit conclusions to be drawn concerning the relative arc resistance rankings of materials which may be subjected to other types of arcs.
The ranking of materials may differ from that found in wet tracking tests (e.g. IEC 60112, IEC 60587 and IEC 61302) and from their performance in service, where the intensity, recurrence frequency and time of exposure to arc discharges are very different.