Study on the optimization of arc extinguishing chamber structure of C4F7N mixed gas circuit breaker

As power-grid voltage levels continue to increase, the structural design and interruption performance of arc-extinguishing chambers in high-capacity C4F7N gas circuit breakers require further optimization. This study used a 252 kV/50 kA self-blast circuit breaker prototype to build a two-dimensional magnetohydrodynamic simulation of the arc-interruption process. Using the Taguchi method, we systematically varied three geometric parameters across multiple simulation schemes: throat length, throat and contact diameters, and height of the expansion chamber. The internal thermo-fluid field evolution and its effect on interruption performance were analyzed. The results show that the throat and contact diameters dominate the thermal dissipation at zero current; both undersized and oversized values suppress arc cooling near zero current, underscoring the need for balanced parameter matching. Moreover, increasing the throat length and height of the expansion chamber accelerates pressure build-up, elevates the peak chamber pressure, and thereby strengthens the gas blast and thermal-interruption capability. These findings provide targeted parameter-tuning strategies and theoretical guidance for the structural optimization of arc extinguishing chambers in high-capacity circuit breakers.