Sparkover Characteristics in CF₃I Gas and CF₃I/N₂ Gas Mixture under Non-uniform Field Gaps

Abstract

A steep-front square pulse voltage generator, which has a rise time of 16ns, a dumping factor less than 2.5% after 10μs duration and a peak value of 200kV, is successfully used to survey the V-t characteristics in nanosecond range. The V-t characteristics of CF₃I, SF₆, CF₃I/N₂ and SF₆/N₂ gas mixtures under non-uniform field gaps by using the steep-front square pulse voltage. When the field utilization factor are measured less than 0.38, the sparkover voltage of CF₃I is lower than that of SF₆. On the contrary, when the field utilization factor is more than 0.38, the sparkover voltage of CF₃I is higher than that of SF₆. The corona inception voltage calculated by using Schumann's criteria and compared with measured one. The V-t characteristics for a uniform field gap in CF₃I/N₂ gas mixture containing N₂ gas of 40% are equivalent to those in pure SF₆ gas. The synergism for appears when CF₃I gas is mixed with N₂ gas.