Effect of the Arc Extinguishing and Insulation Properties of C 4 F 7 N/CO 2 Mixtures with Oxygen Addition: Experimental Investigations and Comparative Analysis

The C 4 F 7 N/CO 2 mixture is considered one of the most promising alternatives to sulfur SF 6 . Recent studies have shown that the addition of O 2 to the C 4 F 7 N/CO 2 mixture can suppress carbon precipitation following electric arc discharges. This paper conducts arc-burning experimental research on SF 6 , 10%C 4 F 7 N/90%CO 2 , and 10%C 4 F 7 N/85%CO 2 /5%O 2 mixtures. Measurements were taken of the arc voltage and arc current under a 10 kA breaking current for these three gases. Additionally, the pressure at the nozzle throat during arc and cold flow conditions, as well as the pressure in the storage chamber, were measured. The post-arc current and Rate of Rise of Recovery Voltage (RRRV) for the three gases were calculated. The study also compared the solid precipitates in the gas medium after multiple arc-burning experiments. The results indicate that adding O 2 to the C 4 F 7 N/CO 2 mixture can increase the pressure at the nozzle throat during the arc phase, and the inclusion of O 2 has minimal impact on the peak arc-extinguishing voltage and critical RRRV. It is hypothesized that a small amount of oxygen has a negligible effect on the thermal recovery properties of the C 4 F 7 N/CO 2 mixture, while also inhibiting the precipitation of carbon following electric arc discharges. This research could provide a reference for developing and optimizing eco-friendly high-voltage circuit breakers.