Calculation of positive static breakdown voltage in rod gaps in SF 6

The peculiar variation of breakdown voltage V_b with pressure p in compressed SF₆ due to corona stabilization of the applied field is well pronounced in rod to plane gaps. In this paper, the space-charge modified field has been calculated and a simple criterion based on the gap minimum field is proposed for breakdown in the rising straight part of the V_b-p characteristic. This calls at first for assessment of the corona onset voltage. For pressures greater than the critical pressure breakdown occurs without any preceding corona discharges and the breakdown voltage is theoretically predicted. The calculated corona-onset V_o and breakdown voltages agreed with those measured experimentally within ±10%