Self-healing Properties of Metalized Polypropylene Film with Elevated Sheet Resistance

Metalized polypropylene films are widely used as dielectric materials in self-healing (SH) power capacitors due to its higher operation electric field, and the SH properties of metalized film directly decided the performance of capacitors. Among all the film parameters, the effects of sheet resistance (R_{\mathrm{s}}, the ratio of metal resistivity \rho to metal thickness d, R_{\mathrm{s}}=\rho/d) played the dominant role, that the higher R_{\mathrm{s}} usually resulted in the better SH performance. As a result, in the present study the SH properties of metalized polypropylene film with elevated R_{\mathrm{s}} were investigated. The morphology of evaporated area of sample films were observed, and four parameters, the dissipated energy (W_{\{sh}}), the evaporation area (S_{\mathrm{v}}), the peak value of short circuit current (I_{\mathrm{m}}) and the duration time (\tau) were selected to characterize the SH performance. Results showed that electric explosion was more likely to happen during SH process when R_{\mathrm{s}} was higher than 35\ \mathrm{\Omega}, which might threaten the stable operation of capacitors. Besides, W_{\{sh}},\ S_{\mathrm{v}},\ I_{\mathrm{m}} and \tau all decreased with the increase of R_{\mathrm{s}}, benefiting the SH process, but the benefits reduced at high R_{\mathrm{s}} level. Considering the higher dielectric losses and financial costs brought by the elevated R_{\mathrm{s}}, an appropriate R_{\mathrm{s}} of 35\ \mathrm{\Omega} was recommended.