Breakdown studies of helium and nitrogen in partial vacuum subject to non-uniform, unipolar fields in the 20-220 kHz range

Abstract

Partial discharges and corona are considered as unwanted processes in electrical power systems since they are constant source of power loss and electrical noise (EMI). These effects can further develop into a major problem at the component level, causing solid insulation deterioration and component failure leading to possible bulk electrical breakdown. The problems are well documented for traditional ground-based (i.e. utility) electrical power systems, and there exists a considerable knowledge base on the subject. However, this knowledge base does not readily extend to on-board electrical power systems in aerospace vehicles because such systems are required to operate at very low atmospheric pressure (i.e. in partial vacuum) and frequencies in the tens of kHz range. Also, much of what is known for aerospace systems is limited to standard 28 V dc systems, whereas the next generation of aerospace systems is expected to operate at higher voltages. Thus, there is an incentive to conduct basic research into corona, partial discharge and gaseous breakdown in gases at partial vacuum conditions, voltages, and frequencies, and for geometries corresponding to the environment encountered in current and future aerospace power systems. This work presents studies on the breakdown characteristics of helium, nitrogen and zero air under unipolar sinusoidal and pulsed voltages at frequencies varying from 20 kHz to 220 kHz in partial vacuum, for a point-to-point and point-to-plane electrode configurations. These voltages are compared to the dc data obtained under similar conditions. Also, breakdown voltage versus pressure curves similar to Pashcen plots are presented. Breakdown voltages of these gases as a function of signal frequency are also presented.