Characterization of point-plane corona pulses in SF6

Abstract

The properties of streamer or electron avalanche pulses have been investigated for point‐plane, and positive and negative dc corona discharges in gaseous SF₆ over the pressure range of 50–500 kPa. Measurements were made of the voltage and pressure dependence of electrically detected corona pulse‐height distributions, pulse shapes, and repetition rates. Positive corona pulses appear at onset as low‐level electron avalanches which, at higher voltages, develop into large streamers usually followed by a burst of many smaller pulses. The burst characteristics of positive corona show a definite dependence on pressure and voltage which is evident in the pulse‐height distribution data. Negative corona displays characteristics which are sensitive to cathode surface conditions. For a point electrode that is either exposed to UV radiation or has been conditioned by prior discharges, the negative corona appears predominantly in a quasiglow mode consisting of relatively low‐level pulses of high repetition rate.