Harmonic resonance and over-voltage assessment during switching of high voltage shunt capacitors in E.R.E.C. network

Shunt capacitors are extensively used in power system for reactive power compensation. Due to the existence of harmonic sources such as arc furnaces, harmonic-producing loads the possibility of harmonic resonance significantly increases. Switching shunt high voltage capacitors may cause over- voltages and this may damage the equipment considerably. In this paper the voltage profile and power losses in the sub-transmission network under study before and after installation of two high voltage shunt capacitors are compared. The harmonic analysis is employed to determine harmonic indexes such as HD in the network buses and to compare the capacitor loading limits with IEEE standard. The effect of the capacitor size on the resonance frequency is determined by using scan frequency analysis. Results show that the resonance frequency may occur in the lower frequency range with respect to the size of shunt capacitors. By considering the exact electromagnetic transient modeling of the network equipment, over-voltages during back to back switching of capacitor banks are also compared with the equipment characteristic.