Interruption characteristic of 3%CFO/97%CO gas mixture in a 40.5 kV circuit breaker

The CFO/CO gas mixture is one of the most promising SF alternative gases at the present stage, which was initially applied in high-voltage electrical equipment. This paper mainly studies the interruption performance of 3%CFO/97%CO gas mixture (k = 3%) with a charging pressure of 0.6 MPa in high-voltage circuit breakers. First, the thermodynamic parameters, transport coefficient, and net radiation coefficient were calculated for k = 3%. On this basis, a 40.5 kV circuit breaker was used as a prototype to establish the magnetohydrody-namic model for breaking 20 kA short-circuit current, and the arc temperature and pressure distribution in the arc extinguishing chamber of the circuit breaker were calculated. The LC oscillation circuit was used to build an arc-extinguishing characteristic test platform to verify the accuracy of the numerical calculation. Finally, based on the Mayr arc model and the critical electric field strength, the post-arc thermal breakdown and electrical breakdown characteristics of SF, CO, and k = 3% were quantitatively analyzed. The results show that under 0.6 MPa, the thermal breakdown performance of k = 3% is about 89.7% of SF, which is nearly twice higher than that of CO and has better thermal breaking ability. The electrical breakdown performance of k = 3% is about 20.4% of SF, and the probability of electrical breakdown in the front end of the fixed contact is high. This problem should be paid attention to in the design of high-voltage circuit breakers. This study can provide a reference for the development and optimization of environmentally friendly high-voltage circuit breakers.