High frequency microdischarge detection technique for electrical insulation and capacitors

Today's modern electrical devices are increasingly subject to, and must withstand, high frequency stressing. Such stressing contributes to accelerated aging of electrical insulation and has resulted in premature failure of components. In order to understand the aging mechanisms (i.e., microdischarge induced erosion, thermal runaway, etc.) and make valid conclusions regarding the service lifetime of components used under high frequency conditions, the electrical insulation must be examined under those same high frequency conditions as those in which it will be used. Conventional electrical techniques used to detect partial discharges are limited to below 2 kHz applied ac test voltages. A new technique was developed, in order to stress electrical insulation and examine the microdischarge activity for frequencies up to 100 kHz. This technique uses series resonance to achieve a high frequency sinusoidal steady state ac test voltage and a bridge type test cell to detect the resulting microdischarge activity. Experimental discharge traces are consistent with simulations, showing improved source voltage attenuation compared to conventional techniques. In addition, the calibration technique shows a critically damped single pulse per discharge event with a temporal resolution of <0.5 μsec. Experimental results are presented.