A statistical approach to the streamer breakdown criterion in SF6

The electrical breakdown field strength in SF6calculated from measurements has been found to deviate considerably from the values predicted by the theoretical models used up to now. The simplest form of the streamer criterion predicts breakdown to take place at field strength - to - pressure ratios close to 8.9 kV/mm atm. The streamer model can be enhanced by introducing surface roughness and electrode curvature factors, thus explaining some of the experimental results obtained. The model is, however, unable to explain the general dependence of the breakdown field strength on parameters as pressure, electrode area and voltage waveform. This paper gives a new theoretical model for impulse breakdown in SF6, using a statistical approach to the streamer breakdown criterion. Field emission is assumed to be the source of primary electrons. This model gives correspondence with the experimental results for different electrode configurations covering a wide range of pressure and electrode area.