Lightning impulse study of SF6/N2 mixtures with 0.1% to 20% SF6 content for rod-plane G\PS with both positive and negative voltages

Abstract

Lightning impulse (1.2/50μs) study of both positive and negative breakdown voltage characteristics of SF6/N2 mixtures with 0.1% to 20% SF6 content for rod-plane gaps over a large range of gap spacings are presented. The range of parameters investigated vary from 5 mm to 100 mm in gap spacings, from 1 to 5 bar (0.1 to 0.3 MPa) in gas pressure. Increase in the 30% breakdown voltage (V50) has been observed to be uniform over the pressure range 1 to 4 bar for both polarity voltages, and under negative voltages, the change is significant only at pressures greater than 4 bar. It has been also observed, that the characteristic ‘pressure-effect’ is not well defined in these gas mixtures and can be seen only over a limited range of experimental conditions (e.g. at 40 mm and 80 mm negative rod-plane gaps).