Abstract: High voltage circuit breaker is the most important protection and control apparatus in power system. The hydraulic operating mechanism is the core part of circuit breaker. The characteristics of hydraulic operating mechanism in circuit breaker are high speed, short operating time and high pressure. The working principle of hydraulic operating mechanism of 550 kV high voltage circuit breaker is introduced. Simulation models of electromagnet, high-speed great flow control valve and hydraulic cylinder are built. The response time of control valve, opening and closing velocity and pressure loss in pipe are discussed. Experiments are carried out to test the pressure, displacement and velocity of hydraulic system. The simulation results prove the accuracy of the models, thus providing the basis for optimizing the performance of hydraulic operating mechanism.

Key words: Circuit breaker, Control valve, Hydraulic operating mechanism, Opening and closing motion, Response time