Comparison of partial discharges in pure SF6 and 5% SF 6-N2 gas mixture

The data on partial discharge performance of actual gas insulated systems filled with an SF₆-N₂ 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 SF₆ gas insulation and the equivalent 11.5 bar 5% SF₆-N₂ mixture gas insulation