Generators are removed from service and reconnected to the power system for various reasons: variations in load, maintenance and emergency outages, to name a few. Each time that a generator is returned to service it must be synchronized with the power system before the interconnecting breaker can be closed. Synchronizing is the act of matching the magnitude and frequency of the generator and system voltage and bringing the two voltages into phase alignment. A failure to properly synchronize can result in electrical and mechanical transients that can damage the generator, prime mover, GSU transformer, and severely perturbate the power system.