Propagation characteristics of impulse creepage discharge in N2/SF6 gas mixture

From the viewpoints of mitigation of global warming, technological strategies for the recycling and minimum consumption of SF₆ gas are under development. Alternative insulation gases and gas mixtures for SF₆ gas are promising in order to meet this problem. This paper describes the creepage discharge propagation characteristics and their mechanisms in N₂/SF₆ gas mixtures for different mixture rate of SF₆ gas under positive lightning impulse voltage application. The authors simultaneously measured current and light intensity pulses and propagation speed of the creepage discharge. Experimental results revealed that the creepage discharge in gas mixtures propagated stepwise by the repetitive process of streamer propagation and streamer-leader transition. The streamer-leader transition time as well as the step length in gas mixtures approached to that in pure SF₆ gas by only 5% mixture of SF₆ gas