Aging of impregnated PP films under high ac electric fields

Polypropylene films impregnated with benzyltoluene were aged at different electrical fields (100 V/sub rms///spl mu/m180 V//spl mu/m), bright points and intense discharges were observed, the film very quickly broke down. At about 130 V//spl mu/m, an epoxy additive was an effective stabilizer of the dielectric. At higher fields, bright discharges were observed and the life-time of the model capacitor decreased quickly with the applied voltage, reaching values shorter than those without epoxydes.