Surface field dynamics in dc film capacitors under an impulse voltage perturbation

For metalized polymer film capacitors, the dynamics of electric field on the electrode surface and its resulting energy dissipation influence the onset and scale of breakdown discharges within the capacitor unit, which in turn is indicative of the reliability and lifetime. To gain an understanding of the dependence of surface electric field on key system parameters, an equivalent circuit model is developed to simulate the temporal evolution of the electric field distribution within a dc film capacitor subjected to an external impulse electric stress. A mosaic pattern of electrode segmentation is taken into account by means of an effective surface resistance and its effects on surface electric field and energy dissipation are computed numerically. Also considered are the effects of the number of electrode segments across a given length. In addition, electric energy dissipation is calculated to assess the level of possible temperature rise within the capacitor. By addressing these two issues, it is shown that the numerical code developed and its underlying methodology can serve as a complimentary tool to the present practice of capacitor designs and performance assessment.