Review of generation system overflux limiters and protection and consequences of incorrect settings

This paper presents a brief review of the coordination issues between the settings for generator automatic voltage regulator (AVR) overflux (V/Hz) limiters and monitors and the overflux protection relay settings. Recent blackouts have caused NERC (North American Electric Reliability Council) to develop standards for coordination of generator excitation control and protection with the aim of improving overall system reliability. The paper considers some practical issues encountered when coordinating protection to ensure generators remain on-line whenever possible to support the power system whilst remaining within recommended limits to ensure maximum equipment lifetime. Consequence of incorrect overflux setting is presented.