STREAMER AND LEADER FORMATION IN SF6 AND SF6 MIXTURES UNDER POSITIVE IMPULSE CONDITIONS .1. CORONA DEVELOPMENT

Streamer propagation and the streamer to leader transition have been thoroughly investigated for SF//6 and air/SF//6 mixtures under positive impulse conditions. This paper, being the first of two related papers on the matter, concentrates on the streamer corona. Streamer propagation in strongly electronegative gases is found to require the average applied field along the streamer path to be close to critical rather than being characterised by a lower 'guiding field'. A theoretical explanation for this behaviour is given. The improved understanding of streamer propagation allows the prediction of corona extensions and corona charges.