QUANTITATIVE EVALUATION OF BACK-TO-BACK CAPACITOR SWITCHING TRANSIENT CONTROLS AT POWER SUBSTATION

Abstract

Shunt capacitors have been widely used for regulating the voltage module at various voltage
levels in power systems. The daily variation of loads requires capacitor switching in order to
appropriately adjust the amount of compensating reactive power injected into the power system.
Apart from the technical effect that the utilization of shunt capacitors can offer, it leads to several
unexpected consequences. Hence, a shunt capacitor system is commonly either equipped with
some elements to mitigate the negative impact due to capacitor switching transient or combined
with the appropriate selection of switching time points. This article presents the spectral analysisbased technique to evaluate the back-to-back capacitor switching transient controls. The
mitigating methods that are investigated include the use of a series inductor to the capacitor,
capacitor switching via an additional resistor, and the installation of an inductor between two
capacitor banks. Each method applied to 110kV capacitor banks of 220kV Mai Dong substation is
simulated. The capacitor voltages and currents are recorded and analyzed by using the algorithms
of STFT (Short-Time Fourier Transform). Simulation results show that the magnitude of high
frequency can be used to indicate the effectiveness of each method.