800 kV Fast Circuit Breaker: Mechanical Coupling Modelling, Buffer Design and Development

The 800 kV fast circuit breaker (CB) used in ultra‐high voltage (UHV) converter transformer can reduce the total breaking time to 25 ms. It significantly improves the action speed and breaking capacity of the CB, with promising broad application prospects. However, fast CBs can generate significant impact and vibration during fast operation. It may threaten the mechanical life and reliability of the CB. This article proposes a modelling method for the fast CB, which couples the multi‐physical fields of the Thomson coil release system (TCRS) and the hydraulic system. It can describe the entire process of the opening action. Based on the simulation model, the buffering processes of the TCRS and the hydraulic system are calculated and designed, respectively. A throttle valve provides hydraulic buffering force within the TCRS oil circuit. The stepped buffer column, combining cylindrical and conical buffer structures, balances the buffer force and achieves steady deceleration. Based on these design parameters, an 800 kV fast CB is successfully developed, validating the accuracy of the simulation calculations. Results indicate that the TCRS tripping time is 2.62 ms, the CB breaking time is 7.92 ms, and the mechanical life of the CB is 10,000 times.