New Approach to Breakdown Study by Measuring Pre-Breakdown Current in Insulating Materials

Abstract

A technique of measuring current prior to breakdown was introduced. The breakdown mechanism was discussed on the basis of results obtained for polythylene (PE) and polymide (PI) by applying dc ramp voltage. At 90°C the pre-breakdown current of PI sharply increased from about 1 msec before breakdown. For PE, the sharp current increase could not be detected till about 100 ns before breakdown, which is the resolution limit of the measuring system. If this sharp increase is due to the temperature rise of the sample, thermal breakdown may be dominant in the case of PI but not of PE.