Get in step with synchronization

This paper presents a review of powersystem synchronization. When two sources are paralleled, it is crucial to close the interconnecting circuit breaker when both sources are in voltage, frequency, and phase coincidence. Operators can synchronize manually, or use the latest, state-of-the-art autosynchronizers (ANSI/IEEE device 25A) and sync-check relays (ANSI/IEEE device 25) to automate closing. Generator and bus synchronization share most principles, with some important differences for each type of synchronization. For generation plants, closing manually or applying an automatic synchronizer depends a lot on the plant configuration and operating mode. For bus-line applications, synchronizing depends on power-system stiffness, motor loads, and whether a wye-delta transformer is between the line and bus. Methods for attaining proper synch-check and fast synchronization are discussed.