Modeling of a discharging cavity in a dielectric material exposed to high electric fields

Partial discharges are localized electric discharges that do not bridge the electrodes. For high voltage components measurements of partial discharges are commonly used to diagnose the condition of the insulation system. Traditionally partial discharges are measured at a single frequency of the applied voltage. However the rather newly developed technique of Variable Frequency Phase Resolved Partial Discharge Analysis (VF-PRPDA) makes it possible to measure partial discharges at variable frequency of the applied voltage. The benefit of varying the frequency is that more information about the state of the insulation system is obtained than from measurements at a single frequency. This paper presents a model of partial discharges in a cavity at variable applied frequency. The aim of the model is to increase the physical understanding of how the frequency of the applied voltage affects the partial discharges in the cavity. This paper studies the influence from the statistical time lag on the frequency dependent discharge sequence and results from simulations are compared with measurement data. The model is a 2D time dependent FEMLAB model in PDE mode which is handled from a MATLAB script.