LOSS OF FIELD SOLID STATE RELAY FOR PROTECTION OF SYNCHRONOUS MACHINES

ABSTRACT

In synchronous machines, extremely low excitation currents may result from a fault in the excitation circuit, malfunctioning of the excitation system, or an unduly low excitation setting. Regardless of cause, if abnormal low excitation continues, it may cause excessive heating in the end fingers of the stator and even thermal damage to the stator if it results in an excessive stator current. Low excitation can also cause instability between the machine and the remainder of the system. In this paper a Silicon Controlled Rectifier (SCR) based relay and breaker for the loss-of-field protection of small size synchronous generators is presented.