Comparison of partial discharges in pure SF/sub 6/ and 5% SF/sub 6/-N/sub 2/ gas mixture

The data on partial discharge performance of actual gas insulated systems filled with an SF/sub 6/-N/sub 2/ mixture in service is scanty, although considerable research has gone into the breakdown in gas mixtures. In this paper different aspects to understand the behaviour of a partial discharge have been studied such as the dielectric properties of insulating gases, its inception voltage, effect of gas pressure on PD magnitude and phase-resolved PD patterns, etc. For this study different types of PD sources have been used. Considerable differences have been observed between 4.5 bar SF/sub 6/ gas insulation and the equivalent 11.5 bar 5% SF/sub 6/-N/sub 2/ mixture gas insulation.