Self-healing of capacitors with metallized film technology:: experimental observations and theoretical model

Capacitors made of metallized polypropylene films suffer partial discharges, called self-healing, due to weak electrical defects. Those defects are destroyed by an electrical arc that extinguishes when enough metal of the electrodes is vapourized around this point. From experimental results, we have elaborated a model of the self-healing phenomenon. The present work shows that the volatilized area of self-healing is mainly due to the Joule heating of the metal by the current pulse induced by the local breakdown, and the local discharge stops (=arc extinction), although the voltage applied to the film remains constant, when the power density becomes lower than some critical power density.