Effect of surface roughness and curvature on streamer inception and breakdown of N2/SF6 mixtures

N₂/SF₆ mixtures are in use for Gas Insulated Lines (GIL). They consist mainly of nitrogen like natural air since they acquire already at low SF₆ contents high dielectric strength. The general basic properties of N₂/SF₆ mixtures have been investigated over decades. But for the design of insulated systems such mixtures and pure SF₆ of equal dielectric strength have to be considered for the choice of the mixture ratio, the pressure and permitted field stress. The essential properties of such mixtures and the influence of electrode curvature and roughness are regarded. The applicability of the findings is confirmed by experiments.