Influence of polarity and field non-uniformity on the breakdown voltage characteristics of SF/sub 6/ gas under impulse voltages

A comprehensive study of electrical breakdown in SF/sub 6/ gas has been carried out under both polarities of lightning impulse (1.2/50 /spl mu/s) (LI) and switching impulse (250/2500 /spl mu/s) (SI) voltages over a pressure range of 0.1 to 0.49 MPa, using a rod-plane electrode configuration with various rod diameters (D) of sharp needle, (D/spl sime/0 mm), 1.5, 2, 3, 6 and 12 mm and for different gap spacings varying from 10 to 100 mm. Experiments were also conducted using 50 Hz a.c. voltages under the same experimental conditions for different gap spacings of 10 and 20 mm. The influence of field nonuniformity, the polarity and the type of voltage on the breakdown voltage characteristics of SF/sub 6/ gas have been analyzed. The impulse ratios have been calculated and their variation have been explained in terms of fundamental physical processes.<
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