New trends in protection relays & substation automation systems in Japan

This paper describes the status and trends of the technical activities ongoing, as well as background circumstances, in protection and control systems in Japan to achieve ensuring stable power supply, improving efficiency, reducing cost, and protecting the natural environment at the same time. Several remarkable measures and systems accomplished to establish a reliable power supplying network system are reported. Current status on applying IT technologies to wide area communication and substation facilities are explained with several examples. Approaches to improve the reliability in the distribution substation are presented, followed by the anticipated effects by introducing of distributed generation systems into the distribution networks.