CO2 as an Arc Interruption Medium in Gas Circuit Breakers

CO2 is a possible alternative to SF6-which has a high global warming potential-as the interruption medium in gas circuit breakers. The performance of CO2 is investigated in this paper by carrying out experiments in representative test devices and by performing computational fluid dynamic (CFD) simulations; some comparisons with SF6 and air are given. It is found that the thermal interruption performance of CO2 is lower than that of SF6, but higher than that of air. The measured dielectric recovery after arcing is compared for CO2 and SF6; a streamer model is used to calculate the breakdown voltage in CO2; good agreement with measurement is found. The speed of sound and the adiabatic coefficient, important parameters that influence pressure buildup and gas flow, are compared for SF6, CO2, and air. CFD simulations of the pressure buildup in CO2 and SF6 both illustrate the qualitative differences between the two and show good agreement with measurements.