Temporal evolution of electric field distribution and energy dissipation in a metallized polymer film capacitor under DC, AC or nonsinusoidal voltage stresses

Abstract

Temporal evolution of electric field distribution and its resulting energy dissipation in a metallized polymer film capacitor is an important indicator of the scale of breakdown discharges within the capacitor unit when it is subjected to an external voltage stress. To gain an understanding of the dependence of breakdown discharges on the characteristics of the external voltage, an equivalent circuit model is developed to simulate the dynamics of the field distribution under three different types of voltage stresses, namely DC, AC, and non-sinusoidal. Pattern of the electrode segmentation is taken into account by means of an effective surface resistance. Also included are the effects of the number of electrode segments cross a given length. Electric field distribution and its temporal evolution are computed and the peak electric field is calculated to provide an indication of the likelihood of surface flashover between two adjacent current gates. In addition, electric energy dissipation is calculated to assess potential temperature rise within the capacitor and so its implication on uncoupling of distant current gates. These calculations are repeated for different values of surface resistance and segmentation number such that certain guidelines for capacitor design can be drawn.