Controlled Switching of HVAC Circuit Breakers: Application Examples and Benefits

Controlled switching technology, that is, predefined controlled strategies for closing and/or opening each independent circuit breaker pole, is an effective way to reduce switching transients, prevent equipment failures, and improve power quality. The paper presents a tutorial on controlled switching of high-voltage ac (HVAC) circuit breakers and describes the controlled switching theory and technology that is in use today. The paper discusses the benefits of controlled switching and shares one utility's applications and experiences with the controlled switching of shunt capacitors, shunt reactors, transformers, and lines, using modern protective relays and control devices. The paper also discusses how to select the optimum controlled switching times to reduce switching transients.