Accelerated degradation of capacitor PP films under voltage distortion

The effect of voltage distortion, that is, of nonsinusoidal supply voltage, on aging acceleration of PP films for ac capacitors is here investigated. The voltage endurance of PP films subjected to life tests under various combinations of sinusoidal and distorted voltage is derived as function of characteristic parameters of the supply-voltage waveform, i.e. peak and rms voltage, as well as waveshape slope. Life tests are performed in oil, in the absence of significant partial discharges, in order to focus the investigation on intrinsic aging. Comparisons are made with the results obtained for low-voltage capacitors. It is shown that for both capacitors and PP films, the prevailing degradation accelerating factor is voltage-peak amplification.