Proposed theory for critical avalanche and corona threshold in nonuniform air-gaps subjected to positive impulse voltage

The present paper deals with a theoretical analysis of the inception mechanism of the “positive streamer-discharge” in air, at atmospheric pressure, in nonuniform fields under impulse applied voltages. The author discusses the two steps involved in the analysis of streamer threshold. The first is to show under what conditions a seed electron generated near the highly-stressed electrode will produce an electron avalanche of the critical size; and hence a streamer discharge. A criterion is proposed which would comprise a correct definition of the critical avalanche and allows a calculation of the threshold field. The second step is to establish an easy yet accurate model to predict the field at which the first corona (streamer) can be initiated