Experiment on breakdown characteristics of SF 6 /CF 4 gas mixtures in short gap

In this paper, researches were carried on the breakdown characteristics of short gap SF 6 / CF 4 , under the flat plate and needle board electrodes, the breakdown voltage of SF 6 /CF 4 gas mixetures was measured when partial pressure ratio of SF6 is from 0% to 100% and the pressure is from 0.1MPa to 0.4MPa, the effects of the gas pressure and other factors on insulation performance of SF6 and its mixed gas were studied. The electron temperature, electron density and other parameters were measured by spectrometer when mixed gas was completely brokenkdown, the correspondence between the micro parameters of gas and macroscopic parameters such as pressure, temperature was established, and the breakdown characteristics of gas were analyzed. The study shows that when ρ SF6 is 20%, the breakdown voltage of gas can reach to 82.26kV under 0.35MPa which equals to pure SF 6 gas under 0.25MPa. When ρ SF6 is 40%, the breakdown voltage of the gas in 0.4MPa can reach 106.8kV, which equals to the pure SF 6 gas under 0.3MPa. Under 0.1MPa-0.4MPa, the electron temperature gradually decreases with the increase of the gas pressure, and gradually increases with the increase of SF 6 partial pressure ratio in the mixed gas. In 0.1MPa, when ρ SF6 is 20%, the electron temperature is 20280K, when ρ SF6 is 80%, the electron temperature reach to 50120K. The electron number density increases with the increase of the gas pressure, and gradually decreases with the increase of SF 6 partial pressure ratio in the mixed gas. In 0.1MPa, when ρ SF6 is 20%, the electron number density is 3.54∗10 17 m −3 , when ρ SF6 is 80%, the electron number density is 3.1×10 17 m −3 . The experimental results can provide a basis for the study of the variation of the conductivity and other physical parameters of the mixed gas plasma.