Abstract:

The rated short-circuit breaking current of 550 kV switches in China urgently needs to be increased from 63 kA to 80 kA. Moreover, the self-blast circuit breakers have great advantages in large-capacity breaking. By constructing a magnetohydrodynamics model considering the continuous motion of multiple valves, a simulation analysis of the arc breaking process for a 550 kV self-blast circuit breaker under short-circuit currents of 63 kA and 80 kA is carried out. The force and motion characteristics of the check valve, the gas return valve and the pressure relief valve are obtained. The study shows that the force characteristics of each valve are similar under different short-circuit currents. The larger the short-circuit current is, the earlier the closing time of the check valve is, the higher its motion speed is, with a peak value of 25.5 m/s, and the more sufficient the mixing of hot and cold gases in the expansion chamber is. The gas return valve remains stationary relative to the right side wall during the arcing stage. The pressure relief valve makes a reciprocating motion on the right side of the initial position after 3.90 ms of arcing, and the farthest distance can reach 339.54 mm.

Key words: large-capacity, self-blast circuit breaker, magnetohydrodynamics, arc breaking, valve