No. 1127
	Failure Extension Prevention Technology by Frequency Relay System Investigating R�•D committee on Failure Extension
	Prevention Technology of Frequency Relay System
	Keyword : electric power system, failure extension prevention technology, frequency relay system, abnormal frequency, supply and demand imbalance
	A large-scale power sources have been developed in Japan corresponding to the increase of the electric power demand according to economic development. Reliability in the electric power system is improved by constructing bulk power systems suiting to the power sources' development, and the stabilized operation has been achieved despite those power supplies comparatively concentrate on the remote place. Under the situation, this committee has been investigating current state of failure extension prevention technology by frequency relay system and its trend in the future for two years from July, 2006 to August, 2008. The frequency relay system is one of the failure extension prevention systems and it is a system that prevents the spreading of adverse effect of abnormal frequency when supply and demand are seriously imbalanced by power supply dropout or load dropout caused by power system outage like power line route stop. This report describes the phenomena of abnormal frequency in the electric power system and the failure extension prevention technology by frequency relay system. This includes "domestic and foreign operation case" and "trend and problem in the future" in addition to "feature of the system composition" and "composition and application of frequency relay system" of each electric power company. This report aims to become a technological resource not only for engineer‚“ involved in the protection relay but also all the people engaging in the electric businesses and ,furthermore, the students who study electric power engineering.
	©2007. The Institute of Electrical Engineers of Japan