Study On Overvoltage Protective Measures Of Vacuum Circuit Breaker Used To Switch 20k V Shunt Reactor

The strong arc extinguishing ability of the vacuum breaker easily lead to overvoltage when switch shunt reactor, and that threat the transformer substation's safe and stable running of power system. Therefore, researching the protect measures of the overvoltage is of great significance.This paper analyzes the mechanism and protective technology of vacuum break switching overvoltage. Field test have been finished to research overvoltage when switching shunt reactor, and according to the test results, the simulation calculation, which use of PSCAD/EMTDC simulation software, focus on phase-ground overvoltage and inter phase overvoltage of system. This paper also simulates three kinds of protection measures to research their protection effect: reactor and bus line equipped with inter-phase arrester, reactor equipped with shunt capacitor and reactor equipped with resistance capacitance device.The simulation results show that inter-phase arrester can restrain inter phase overvoltage; shunt capacitor can reduce overvoltage due to current chopping, and the overvoltage amplitude reduces along with the capacitance value growth, but this overvoltage do not change any more when the capacitance over 0.2?F in the 20 kV system, however, reignition overvoltage become stronger as the capacitance value is higher, and it basically do not change any more when the capacitance over 0.3?F. Resistance-capacitance device can also reduce system's overvoltage, however, the protective effect of different resistance is related with reignition: when there is not reignition, only reactor overvoltage reduces along with the resistance growth, but this change is going in the opposite direction while the resistance exceeds a certain value. When reignition occurs, overvoltage of reactor and bus reduces along with the resistance growth, but the bus overvoltage do not change any more when the resistance over 400?.Finally, the paper proposes that reactor should be equipped with shunt capacitor and inter phase arrester, and bus line should be equipped with inter phase arrester to prevent overvoltage. This protection measure is proved to be an effective method through practical operation.