Abstract
A square pulse voltage is useful for studying electrical discharge physics or very fast transient overvoltage issues. This paper describes sparkover voltages and time lag (V-t) characteristics of CF3I gas, which has very low environmental effects and high dielectric strength, and its mixtures with nitrogen gas or air in a very short time range below a microsecond. They are measured by using a steep-front square voltage with a rise time of 16 nanoseconds and a peak value of 200 kilovolts. Pure CF3I gas has 20 % higher dielectric strength than SF6 gas. V-t characteristics of CF3I-N2 or CF3I-air gas mixtures, which contain 60% CF3I gas, are equivalent to those of pure SF6 gas at the same total pressure. A quantitative evaluation of V-t characteristics by the equal area criterion is also performed. The equal area parameter which is obtained by applying a voltage enough high to make the formative time lag dominant should be chosen.
