Investigation of partial discharge life characteristics of twisted pair of enamelled wires

As for motor windings, the influence of deterioration due to partial discharges may have been studied as one of the life determination factors of motors. In this paper, we measured the maximum discharge charge magnitude, φ-n distribution patterns that corresponds to the partial discharge occurrence distribution at applied a.c. voltage phase angle, φ-q distribution that corresponds to the averaged partial discharge magnitude at each applied a.c. voltage phase angle. Those characteristics were measured up to dielectric breakdown by applying a sinusoidal voltage to a twisted pair of enameled wires. The change in the discharge characteristic with time and the applied voltage frequency have been investigated to analyze the life of the twisted pair of enameled wires based on the a.c. voltage frequencies.