Research On Overvoltage Of Using Vacuum Circuit Breaker To Switch35kV Shunt Reactors

Vacuum interrupter breakers with high reliability, long lifetime, merit no fire hazards and ideal frequently operating performance has been widely used in10kV and lower voltage level power systems. In recent years, cases of35kV vacuum circuit breakers being used for switching shunt reactors gradually have increased. However, practical operation experience has shown that overvoltage accidents like phase to phase insulation breakdown and fuse on the high voltage side of bus PT blowing happens frequently, endangering the safe operation of electrical equipment and the whole power system. This has proved that the current normal overvoltage equipment couldn’t protect the equipment properly. The overvoltage protection of using vacuum circuit breakers to switch35kV shunt reactors is still worthy of further research.Based on EMTP software and some220kV substation in Zhejiang Province of China, this paper has simulated the real overvoltage accidents that happened during the operation process of using vacuum circuit breakers to switch35kV shunt reactors. Accoring to fault recording figures, the author has analyzed the mechanism and conditions and realized reappearance of overvoltage accidents. The research has shown that the current closure effect is unavoidable during the switching process. However, the magnitude of current could be under control. The reignition effect is concerned with the materials and mechanical operating system and thus of great randomness. The overvoltage of three-phase opening at the same time is the main reason of high amplitude of overvoltage, which causes continuous current closure and reignition. Instead of the phase that opens firstly, the other two phases are more likely to suffer from higher overvoltage.Using the former model, this paper also studied the overvoltage protection effects of three important overvoltage protection devices. The results have indicated that the regular three star MOA has the similar phase to ground overvoltage protection effect with four star MOA. As for the phase to phase overvoltage protection, the four star MOA would be much better than three star MOA. Another overvoltage protection device called RC absorber is specifically aimed at protecting the overvoltage caused by using vacuum circuit breakers to switch35kV shunt reactors. For the cases studied in this paper, RC absorber has the best overvoltage protection performance. Then this paper compared different installation schemes and concluded that both the bus side and the circuit breaker side should be equipped with overvoltage protection devices. In chapter five another protecting method of adding another circuit breaker right beside the shunt reactor is proposed. It costs much but needs not to concern about the performance or safety of the overvoltage protection device itself. At last, this paper briefly introduced possible lightning invasion and ferromagnetic resonance considering the construction plan of the distribution network in the future.