Partial discharge behavior of a newly developed enamel insulation at various voltage rise times

Investigations of partial discharge (PD) characteristics in twisted pairs are presented. The test objects were made of conventional and chromium oxide filled enameled wires and were exposed to pulse width modulated (PWM) voltages of different rise times. To compare the performance of each insulation system, measurements of both PD inception and extinction voltages were conducted. Additionally, the number of PDs per cycle and their amplitude at different voltage levels were determined. Experimental results showed that the total PD exposure was considerably reduced for the chromium oxide filled enamel insulation as compared to that of the conventional material at the shortest voltage rise time. However, for filtered PWM waveforms with relatively longer rise times this difference became less prominent. The analysis of the results indicated that the observed effects are determined by the presence of chromium oxide filler and its electrical properties.