Measurements of Pressure Wave at Electrical Breakdown in PP Film

Abstract

Electrical breakdown of a polymer film generates the pressure wave, which is considered to include information about the breakdown initiation point. In this paper, we measured the breakdown pressure wave and the space charge distribution up to electrical breakdown field by using pulse electro-acoustic method in a 30μm thick polypropylene film. We discussed electrical breakdown phenomena based on the breakdown pressure wave and the dependence of space charge distribution on applied field and temperature. At room temperature, the observed breakdown pressure wave shapes were pulse-like and the width depended on the polarity of applied field. The positive space charge accumulation was observed near the cathode as a hereto space charge near the electrical breakdown field. At 60°C, the width of breakdown pressure wave showed no dependence of applied field polarity and the positive space charge accumulation was observed inside the film near the electrical breakdown field. These experimental results suggested the electrical breakdown phenomena were affected by the hetero space charge accumulation and the initiation point of electrical breakdown was correspond to the position of hetero space charge accumulation in 30μm thick polypropylene film.