Field verification of controlled switching GCB

Abstract

A controlled switching system (CSS) with an independent-pole-operated gas circuit breaker (GCB) was applied to a 121 kV-capacitor bank and tested in the field. Complete system performance checks have been conducted according to the CIGRE recommendations for evaluation tests. The compensation algorithm of minimizing the scatter of the switching instant as well as the practical approach of determining the optimum switching targets are proposed based on the GCB characteristics identified in the type tests. Any drifts in operating times that associated with the past operations and the idle time of the drives should be included in the compensation algorithm along with the variations of the operating times caused by the operating conditions. The drifts of the operating times caused by a number of consecutive operations can be compensated using an adaptive control, which can predict the operating time for the next operation based on several previous operations. Innovative operating mechanisms such as stable high-pressure hydraulic drives and low-friction spring drives have been developed and demonstrated to minimize the delay of the operating time after a long idle time. The proposed method of determining the optimum switching targets can be applied for the CSS and its effectiveness was demonstrated by the controlled switching tests. The paper also describes the design requirements and the results of the field performance tests in detail.