Optical Emission Characteristics of Helium Breakdown at Partial Vacuum for Point to Plane Geometry

In general, power devices and systems operating in vacuum or space environment are more susceptible to partial discharges, corona, or volume discharge due to the partial vacuum conditions. Partial discharge and breakdown measurements have been performed on electrical equipment operating in such environments for over decades. In spite of all the studies, fundamental understanding of partial discharge or corona initiation has not been understood completely. Various means of detection have been used over the years, including the detection of electromagnetic emissions using antennas or by observing the current through the ground cables to obtain a better understanding. The measurements are usually analyzed together with other techniques like visual inspection, transient voltage/current measurements and acoustic/optical characteristics. In this paper we present our work on optical emission characteristics of breakdown events at partial vacuum for point-to-plane electrode configuration, operating at DC and 20 kHz frequency in helium. A DC-offset-AC voltage source for the high frequency experiments and a pure DC power supply for DC breakdown experiments were used. Preliminary data of voltage and current waveforms along with the light emission data are presented. The optical signal detection of this set-up includes a photomultiplier tube (PMT) and a digital pico-ammeter. Optical data collected by a PMT as a function of time is presented. Presence of optical emission was also recorded by a video camera and frame-by-frame images were used for data analysis.