Multi-Physical Coupling Collaborative Control Mechanism for 550 kV High-Speed Circuit Breaker

This investigation examines the decline in breaking performance observed in 550 kV high-speed circuit breakers, tracing the cause to insufficient coordination between the operating mechanism and the arc-extinguishing chamber. It proposes a coordinated adjustment of the buffer strategy mechanism and the structural parameters of the arc-extinguishing chamber, revealing their interaction under high-speed opening conditions. To address the impact loads and unstable airflow field during the mechanism’s high-speed opening, the buffer strategy was revised by increasing the gaps in the first four steps by 0.3 mm and 0.5 mm in two respective optimization schemes. Set the step size to 3 mm, and assign a decrease of zero for each of the final three steps. A 1 mm gap reduces the pressure drop near the end of the opening phase. The axial airflow velocity and the breaking performance were compared at the moment of 1 ms before current zero for three nozzle throat lengths (L_u): 22 mm, 27 mm, and 32 mm. Nozzle throat length has a clear effect on the main parameters of short-arc quenching. With a 27 mm throat length, the measured values remain relatively high. The proposed length scheme achieves a balanced trade-off between the airflow velocity distribution and the efficiency of arc cooling. Downstream of the nozzle, the axial airflow velocity is 18% higher than in the 32 mm scheme, and the pressure decays 22% more slowly than in the 22 mm scheme. This improves heat removal from the arc and shortens the short-arc phase to under 6 ms. Prototype tests provided by the manufacturer indicate that the circuit breaker with a 27 mm nozzle throat can achieve a minimum arcing time of approximately 6 ms, which is consistent with the simulation prediction.