Surface flashover dynamics in metallized polymer film capacitors

Flashover discharges are one of main failure mechanisms in metallized polymer film capacitors. To study the basic characteristics of surface discharges and their dynamics, an equivalent electric circuit model is developed for metallized polymer film capacitors with the surface discharge modelled with a time-dependent resistor. The discharge resistance is related to the thermal dynamic equation, and as such the heat generated within the capacitor unit can be estimated and subsequently used to assess changes in material properties due to temperature rise. Also discussed are the conditions for propagation of surface discharges and its elongation. For different combination of key system parameters, surface discharges are simulated and this provides insights into factors that influence the growth of surface flashover in metallized polymer film capacitors.