Comparison of partial discharge behavior of epoxy resin impregnated coils under high voltage and high current stress

This paper deals with a comparison of the partial discharge (PD) behavior of epoxy resin impregnated coils under high voltage and high current stress. Due to the availability of a new method, it is possible to conduct PD measurements in combination with a pulsewidth-modulation (PWM) amplifier. By this method, the PD behavior of coils under current stress can be determined. A comparison between the measurement results under voltage and current stress shows, that the PD inception voltages are higher under current stress than under voltage stress. These results suggest, that it is necessary to conduct PD measurements under current stress in order to make an accurate prediction on the PD behavior under normal operating conditions. Furthermore, a new method for locating PD sources is presented. Under special circumstances, it is possible to locate a PD source by a comparison of the PD inception voltages between voltage stress and current stress.