Coordination of the Synchronous Generator Protection with Generator Capability Charts

Abstract

The large generating units are one of the important components in producing electric power to the power system. Therefore, it requires highly reliable protection relays to minimize the possibility of damage occurring under fault conditions. There are varieties of protective relays to provide secure and reliable protection for Synchronous Generators (SG) and Generator Step-Up Transformer (GSUT). The differential protection is a reliable method of protecting generators, transformers, large motors, buses, cables and transmission lines from the effects of internal faults. The main benefits of this protection type are isolating the faulty unit accurately and fast. The generator-transformer unit overall differential protection relay (87O) is designed to be a backup protection for SG, GSUT, and Unit Auxiliary Transformer (UAT) differential protection systems. The setting of the relay (87O) usually coordinated with differential protection for SG, GSUT, and UAT by a time delay, Pickup current, and/or slope of restrained curve to avoid mal-operation during normal operating conditions