Breakdown of Solid Insulating Films by Partial Discharge Using Sinusoidal and Pulse Voltages

An experimental technique is described for measurement of the relative resistance of solid insulating films to breakdown by partial discharge using an IEC(b) electrode geometry together with sinusoidal voltages of frequencies from 1 to 60 kHz and pulse voltages at a repetition rate of 15.625 kHz. The technique is employed for determining the accelerated lifetime of polyimide and PVC films. The temperature rise under discharge condition was also measured. The results show that within the 100 minute time limit of these tests, lifetime is accelerated as the applied peak-to-peak voltage is increased, lifetime is accelerated linearly with frequency, and lifetime is independent of the voltage waveform. The results suggest that life with pulse voltage may be estimated from the results of an equivalent simple sinusoidal voltage test. Temperature measurements indicate that the specimen temperature increases with the applied voltage and frequency. The technique provides a rapid means of evaluating the performance of solid insulating films at a relatively low frequency.