CALCULATION OF OVER RECOVERY VOLTAGE WHEN SWITCHING CAPACITORS IN THE DISTRIBUTION GRID AND PROPOSED SOLUTIONS FOR MITIGATION

Abstract

Capacitors are installed to improve the power factor in the distribution grid. However, the disadvantage of shunt capacitors are that when the capacitor are
switching overvoltage will appear, affects power quality and affects switching equipment (breakers). Therefore, it is necessary to calculate overvoltage when
switching capacitor, in which Transient Recovery Voltage - TRV and Rate of Rise of Recovery Voltage - RRRV are decisive in choosing circuit breakers safely and
economically. This article presents the results of research on calculating overvoltage when switching a single capacitor bank and switching parallel capacitors
bank at a 110kV transformer station. The TRV and RRRV values of Breaker in single and parallel capacitors switching cases are determined and analyzed. In
addition, the overvoltage applied to the capacitor and the inrush current through the capacitor are also determined and evaluated. Research results show that
when the switching capacitor in parallel, the current on the capacitor has a very high value, causing danger to the capacitor. The solution of using surge arrester
combined with shunt reactor installed on the capacitor side is highly effective in reducing TRV and RRRV.