Decay characteristic of gas arc in C₄F₇N/N₂ and C₄F₇N/CO₂ gas mixture by Thomson scattering

Abstract C 4 F 7 N/N 2 and C 4 F 7 N/CO 2 gas mixtures are considered potential alternative gases to SF 6 , and it is of particular significance to investigate the plasma decay process in these mixtures for evaluating their circuit breaker breaking performance. To comprehend the decay process of electron density( n e ) in arc plasma within C 4 F 7 N/N 2 and C 4 F 7 N/CO 2 gas mixtures, an arc-generating circuit and a Thomson scattering experiment platform were established. Through coherent Thomson scattering diagnosis of gas arc plasma under various gas mixture conditions, a series of electron density results over time and space were obtained. The findings suggest that the initial electron density of the arc plasma diminishes with an increase in the proportion of C 4 F 7 N, and electron density decay is further accelerated as the proportion of C 4 F 7 N increases. Moreover, it was observed that the electron density decay rate is higher in the C 4 F 7 N/N 2 mixture compared to the C 4 F 7 N/CO 2 mixture. Notably, the electron decay rate in a 50% C 4 F 7 N/N 2 mixture closely resembles that observed in pure SF 6 .