Application of Surge Arrester on Vacuum Circuit Breaker

A vacuum circuit breaker switching in installations supplying shunt reactor can cause overvoltage transients. These phenomena has been occurred in some distribution network especially in the network which require the application of shunt reactor to compensate voltage amplification due to very low current flow through the transmission lines. This transient problem is generally associated to the high-frequency overvoltage produced by the re-strikes and pre-strikes during the opening or closing of a switching device. The problem is occurred in all circuit breakers type, especially in vacuum circuit breaker (VCB). This paper intends to present a study case of this phenomenon. In this case, failures of a vacuum circuit breaker during shunt reactor bank switching in distribution network have been observed. There has been some evidence that the failures of vacuum circuit breaker have been occurred due to re-striking during reactor switching. Therefore the simulation and experimental investigation were conducted and the results were presented. The simulation was conducted to simulate the transient overvoltage when the switching occurred. Then the results of simulation were compared with experimental investigation in laboratory. The experimental set-up was made to reproduce similar switching re-strikes and fast transients overvoltage as it could be experienced when disconnecting a shunt reactor from the distribution network. Later the simulation was repeated using surge arrester to suppress the transient overvoltage. The surge arrester was also implemented in the experimental set-up. The result from simulation and experimental investigation were compared. Finally the surge arrester was implemented in the distribution network where the vacuum circuit breaker failure had occurred.