Electromagnetic Transient Program Modeling for Switching Over-voltage Analysis in Shunt Reactor

Shunt reactor, a facility for reactive power compensation, is switched several times a day depending on the load pattern. When the circuit-breaker opens the shunt reactor, it interrupts the inductive current near the voltage peak because the current is about 90 degrees later than the voltage phase. At this time, over-voltage generated by several factors degrades the insulating performance of internal parts of the circuit-breaker and causes severe voltage stress on the equipment in the power system. In Korea, shunt reactors are installed and operated in 345 kV substations, and the frequency of failures tends to be very high compared to the operating ratios of the 362 kV circuit-breakers for transmission lines, transformers, etc. Transient phenomenon occurring during the switching of shunt reactor are available in laboratories that verify the performance of the breaker by simulating the power system. However, it is difficult to measure the transient behavior that occurs during actual operations in power system due to many limitations. Therefore, this paper deals with the modeling using EMTP to analyze the reignition and current chopping which causes more severe transient recovery voltage in the inductive small current opening process in actual power systems. In addition, this paper analyzes the main phenomenon that cause circuit-breaker failure in opening shunt reactor using EMTP model.