New investigations of the 'early streamer emission' principle

An 'early streamer emission' (ESE) terminal, for lightning protection? stim ulates a burst of streamers from its tip before producing streamers induced by the field of a downward leader, approaching from a thundercloud. It has been claimed to enhance the probability of attachment of a lightning chann el to a protection system. Experiments are described in which the performan ce of a simulated 'early streamer emission; terminal has been characterised . A negative slow-front impulse voltage has been applied to a plane suspend ed over a vertical rod to simulate the rise of electric field at the tip of the rod, which would be caused by an approaching leader discharge from a c loud. A positive auxiliary voltage impulse, of profile 1/30 mu s, of suffic ient amplitude to produce corona, has been applied independently at the rod at controlled, variable times during the rise of the slow-front field. The effects of this pulse on the corona produced at the rod by the negative im pulse at the plane, on the breakdown voltage of the gap, and on the times t o breakdown have been recorded. The general conclusions drawn are that the auxiliary corona has insignificant effects on breakdown when it is applied during the streamer phase of the slow-front corona, but that it influences growth when applied after the leader has been initiated by the ambient fiel d.