Measurement of sparkover voltage and time lag characteristics in CF 3 I–N 2 and CF 3 I– air gas mixtures by using steep‐front square voltage

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 CF 3 I 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 ns and a peak value of 200 kV. Pure CF 3 I gas has 20% higher dielectric strength than SF 6 gas. The V – t characteristics of CF 3 I–N 2 or CF 3 I– air gas mixtures, which contain 60% CF 3 I gas, are equivalent to those of pure SF 6 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 high enough to make the formative time lag dominant should be chosen. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 1–7, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20325