Negative corona discharge in air with small SF6 content

The influence of small amounts of SF₆ in air was examined over the corona pulse regime, using a plane point-plane geometry at a pressure of 800 Torr. With pure air, normal Trichel-type pulse behavior prevailed. Introduction of 1% by volume of SF₆ into the intervening air-gap space gave rise to drastic changes in the discharge-regime characteristics. Narrower and more intense pulses resulted, and the pulse amplitudes as well as the pulse intervals in the discharge were more broadly distributed: the corona pulse regime exhibited characteristics similar to those found in pure SF₆. Data were statistically treated, and analyzed in terms of the most recurrent values of the current pulse amplitude and associated pulse interval. The variation of these parameters, when taken one by one or in a combination, was found to be sufficient to detect and characterize the observed changes in comparison to the discharge regime in air