Coordination of digital excitation system settings for reliable operation

Today´s digital excitation systems play a significant role in providing fast and accurate voltage control to the power system. Yet, as noted in the past, undesirable consequences can occur if coordination of limiters and protection, internal and external to the excitation system, is not properly addressed. During extreme operation of the generator and excitation system, the reliability of the system can be jeopardized, resulting in an unscheduled machine trip. The importance of the coordination between the excitation limiters and unit protection becomes obvious; but also important are the proper settings needed to ensure reliable transfer to the redundant excitation controller. This paper will address the importance of coordinating the various settings of the excitation system as well as performance checking the voltage regulator and limiter to ensure reliable operation during disturbance events.