Sequential phase energisation technique for capacitor switching transient reduction

The application of a sequential switching scheme for the mitigation of capacitor switching transients is presented. The method utilises neutral grounding impedance connected at the neutral point of the switched capacitor bank together with sequential pole switching. The neutral impedance is sized to minimise the open-circuit contact voltage of the capacitor breaker phases. Theoretical analysis of the proposed scheme has been carried out together with computer simulation. In addition, neutral impedance sizing criteria are presented in order to achieve minimal transient over-voltage caused by capacitor switching. The proposed method was found capable of reducing the transient over-voltage at the utility switched capacitor location to 1.07 and 1.12 p.u. at the customer load bus.