Simulation of Void Discharges and Time Domain Examination of Their Emitted Electromagnetic Signals

The goal of this paper is to present the time domain behavior of the emitted electromagnetic signals of void discharges and to show the design process of the measured partial discharge (PD) sources. After the introduction of the used physical models and equations, the finite element calculations used to create a modified empirical ignition criterion for the discharge and to determine the optimal dimensions of the samples are presented. Using these sizes, two void discharge sources were created by including different diameter air bubbles in a thin layer of epoxy resin between two electrodes. After this, the emitted electromagnetic signals of the sources were measured using a noise-free GTEM cell and a digital sampling oscilloscope. From the measured signals, PRPD patterns have been created to examine the activity of the emitted void discharge signals as the function of the phase angle of the AC testing voltage. This was followed by the examination of the effect of bubble size on the PRPD characteristics. The results of the emitted measurements were consistent with the conducted measurement results of the literature and the partial discharge physics based model of the air-filled cavity.