Electrical aging and electroluminescence in epoxy under repetitive voltage surges

Abstract

An extensive statistical accelerated aging experiment, involving a total of 180 unfilled type epoxy specimens, has been conducted to determine the number of voltage surges required to initiate electrical trees under various magnitudes, surge repetition rates, and polarity conditions. The specimens were tested one at a time according to a full factorial experimental design. During many of the aging tests, the electroluminescence (EL) from the epoxy specimens was monitored. Conventional Weibull analysis techniques were used to investigate the experimental results. The analysis showed that life decreased with increasing applied voltage and was longer for negative polarity surges. As the surge repetition rate increased, the number of surges to initiate a tree increased. A modified inverse power model, with a voltage power law constant similar to that found in AC aging was determined to be appropriate. No correlation was observed between either the trend in EL over time or the total amount of EL and the number of surges required to initiate a tree.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>