The critical parameters, while synchronizing a synchronous generator to an electrical system, are delta phase angle, delta frequency, and delta voltage magnitude. Severe system disturbances as well as damage to the generator, prime mover, and generator breaker may result if the generator is allowed to connect to the system outside established levels for these parameters. Therefore, protection is required to ensure that tolerable levels are not exceeded during the synchronizing operation. A manual/automatic synchronization circuit has been designed for a 37.5-MVA generator with protection for all three critical synchronizing parameters. To make sure that one protective device failing does not leave the generator without protection during synchronization, double redundant or triple redundant devices are often used. The manual/automatic synchronizing circuit detailed in this paper uses triple redundant protective levels for both the manual and automatic circuits. The first and second protective levels are shared by both circuits being a solid-state automatic synchronizing relay in tandem with a solid-state synch check relay. An operator/synchroscope provides the third protective level for the manual circuit, while a microprocessor-based governor provides the third protective level for the automatic circuit. The philosophy, design, and operation of this manual/automatic synchronization circuit is reviewed. © 1990 IEEE
