In this paper on partial discharges due both to applied Laplacian field and to charged surface of a plate-covering dielectric sheet, separate positive and negative precharging polarities were used in selective point-plane corona experiments in atmospheric air. At a finite point potential, three distinct regimes were encountered: (1) Trichel-like pulsing; (2) discharge quenching; and (3) inverse pulsing. A quenching-potential threshold separating regimes 1 and 2 and an inverse-pulsing triggering potential threshold separating regimes 2 and 3 were determined as functions of the precharging voltage for the physical parameters of the system used. In regime 3, inverse-pulsing current signatures indicate some features shared in common with the more familiar Trichel pulsing. Also noted is the phenomenon of pulse bunching, observed when conditions lie close to those of the threshold of inverse-corona pulsing, whereby groups of such pulses, typically a few in each, would recur in quick, but irregular succession.
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