Three‐phase resistive capacitor switching transient limiter for mitigating power capacitor switching transients

Abstract

This study presents a new resistive capacitor switching transient limiter (RCSTL) for mitigating power capacitor switching transients. The RCSTL is composed of three limiting resistors, a three-phase full bridge diode rectifier, a thyristor and a three-phase coupling transformer. The limiting resistors are connected in series with the capacitor bank and the thyristor is installed at the DC side of the diode rectifier. During the capacitor bank energising, the thyristor remains off and hence, the secondary side of the coupling transformer acts as open circuit. Consequently, high impedance including the transformer's magnetic reactance in parallel with the limiting resistors is inserted in series with the capacitor bank. Under such circumstance, the limiting resistors restrain the capacitor switching transients. In the steady-state, the control system triggers the thyristor and the coupling transformer acts as short circuit. As a result, the limiting resistors are bypassed by the coupling transformer and thus, the RCSTL has no significant effect on the circuit. Analytical analysis is performed to describe different operation modes of the proposed RCSTL. A single stage of a three-phase wye-connected capacitor bank with 25 kVAR is energised and the performance of the proposed limiter is investigated. Both the simulation and experimental results confirm the effectiveness of the RCSTL.