Calculation Method and Influencing Factors of the Maximum Breaking Current of SF₆ Circuit Breaker

At present, there is a lack of research on the evaluation of the maximum breaking current of circuit breakers in arc simulation of SF6 circuit breakers. Therefore, a coupling simulation model of electromagnetic, thermal, fluid and radiation physical fields is established for the breaking process of circuit breakers, and a breaking criterion based on temperature distribution is proposed to study the changing law of the maximum breaking current of circuit breakers. It is found that the ablation angle of the contact decreases the maximum breaking current ability of the circuit breaker rapidly. For the 126 kV circuit breaker, the maximum contact ablation angle to achieve the rated breaking condition is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12\sim 13^{\circ }$ </tex-math></inline-formula> of ablation from the intact contact angle. When the opening speed decreases, the maximum breaking current decreases as a whole, and the breaking capacity decreases the most when the contact is intact, but there is still a large margin from the rated current value. The maximum breaking current decreases with the increase of the breaking phase angle. When the breaking phase angle is [<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.8\pi $ </tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.9\pi $ </tex-math></inline-formula>], the circuit breaker cannot be broken in rated working condition. The research results will provide a theoretical basis for SF6 circuit breaker engineering to break short circuit current.