Controlled Switching

Abstract

Controlled switching systems (CSSs) have become an economical solution and are commonly used to reduce switching surges for various switching applications (CIGRE TF 13.01 1995, 1996). Recent developments of transformer switching taking account of the residual flux can effectively mitigate severe inrush currents and temporary overvoltages that may lead to false operation of protective relays and degradation in power quality. CSS combined with metal oxide surge arresters can reduce undesirable overvoltages caused by energization of a long transmission line and contributes to the optimization of insulation coordination. The limited number of applications for line switching in service up to 2005 may arise from initial difficulties due to insufficient technical considerations; however, the applications recently increase with a controller with highly processing capability. IEC62271–302 Technical Report titled “High voltage alternating current circuit breakers with intentionally non-simultaneous pole operation” was published to standardize the testing procedures required for CSS based on the recommended evaluation tests by CIGRE WG A3.07 (CIGRE WG13.07 1999, 2001). The CIGRE guide emphasizes the importance of compensation for the variations of the operating time because a CSS requires accurate operation consistency during the lifetime of circuit breaker. Variations of the operating times due to external variables such as ambient temperature, control voltage, and mechanical energy of the drives can be compensated by the controller using dependencies evaluated according to the testing requirements.