SIMULATION OF CORONA DISCHARGE - POSITIVE CORONA IN SF6

Positive coronas in SF6 under three voltage levels, 3.0, 3.5 and 4.0 k V, are studied for a 0.5 cm gap between a hyperboloid needle and a pla ne electrode at a gas number density N = 2.12 x 10(18) cm3. The curren t in the form of a burst of pulses is found to increase with increasin g voltage. The initiation and development of successive avalanches are traced as function of time after voltage increases. The development o f electron avalanches and streamers are due to ionization and photoion ization and quenching of avalanches is due to space charge. The simula tion provides a detailed structure of avalanches from which essential differences between positive and negative corona with regard to total field distribution, propagation of successive avalanches and ion distr ibution can be discerned.