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

Abstract C4F7N/N2 and C4F7N/CO2 gas mixtures are considered potential alternative gases to SF6, 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(ne) in arc plasma within C4F7N/N2 and C4F7N/CO2 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 C4F7N, and electron density decay is further accelerated as the proportion of C4F7N increases. Moreover, it was observed that the electron density decay rate is higher in the C4F7N/N2 mixture compared to the C4F7N/CO2 mixture. Notably, the electron decay rate in a 50% C4F7N/N2 mixture closely resembles that observed in pure SF6.