Inrush current investigation of capacitor bank switching for 150kV electrical system in Indonesia

Abstract

Circuit breaker (CB) installed for capacitor bank is the CB which commonly experiences the switching process due to the capacitor bank function as a voltage regulator. In closing switching process, CB encounter transient condition due to inrush current. In this paper, the simulation for studying the inrush current characteristic of capacitor bank switching in Indonesia has been performed. Simulation results show that the inrush current for isolated switching complies with the IEC standard. However, for the back to back switching, the inrush current exceeds the standard's allowable limit. By the measurement data, the contact resistance value for the CB with the back to back switching condition has a highly different value for each phase, and it tend to broke the CB. To mitigate the inrush current, damping reactor utilization has been studied and the results showed that the damping reactor can minimize the inrush current value by tuning the right value of damping reactor inductance related to reactive power of capacitor bank.