AC degradation of impregnated polypropylene films

The aging of impregnated polypropylene (PP) film has been carried out on capacitor models at 80 degrees C under 50 Hz AC electrical stress (137 V/sub rms// mu m). The damage was estimated from the local measurement of the breakdown voltage of the PP film. The effects of impurities (electrolyte, water, oxygen) added to the impregnating liquid were observed. The relatively low breakdown voltages of the aged film measured in the electrically stressed region were no longer found when the liquid contained epoxides. A chemical degradation analyzed by FT-IR microspectroscopy and gel permeation chromatography was observed and found only in the region of lower dielectric strength.<
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