Research On Generator Circuit Breaker Based On Phase Controlled Switching Technology

Phase-Controlled switching, also named synchronous switching or phasing controlled switch, is applied to the principle of coordinating the instant of opening or closing of a circuit with specific target point on a favorable voltage or current waveform. Controlled switching is an economical solution to reduce switching surges or to increase its breaking capacity. It is one of the advanced subjects of intelligent apparatus. To increase the breaking capability and the reliability of generator vacuum circuit breaker, the theory of generator vacuum circuit breaker has been analyzed in this paper. Based on the developed reliability model of generator circuit breaker, the synchronous control system is designed. The obtained results in this paper supply references to the further research of the synchronous generator vacuum circuit breaker.To increase the break capability of generator vacuum circuit breaker, a parallel switching method has been introduced. The related mathematic model of parallel switching is established. The transfer time of the branch current and the asynchrony are analyzed. The concrete method is presented to solve the parallel switching.The basis of Phase-controlled switching is to judge the short circuit fault exactly. Generator circuit breaker is located on the exit of the generator. The switching of the equipment and the circuit can cause the transient phenomenon. It is necessary to distinguish between the normal state and the fault state of the system. A distinguishing system applying the wavelet principle is designed in this paper. The switching strategy based on the Poltl algorithm is applied to control switching of the generator fault current.Due to the perfectly match characteristics, permanent magnetic actuator (PMA) has been widely used by vacuum circuit breaker. Based on the mathematical model of PMA, the dynamic characteristic is analyzed. The fault tree of the generator circuit breaker is constructed to increase the reliability of generator vacuum circuit breaker.The controlled switching system applied the combination of the MC68332 and FPGA. The design of software and hardware for the control system is presented. In this system, MC68332 is used as the kernel. The FPGA realize the real-time sampling and the wavelet Transform. Thus the control precision and the arithmetic speed of the system are improved.Based on the above theoretical analysis, a prototype device of generator circuit breaker using PMA has been built based on controlled switching. Experiment results show that the operation of prototype device is stable and reliable. The deviations of actual switching instants are less than 1ms. The inrush current and restrike are effectively eliminated.