New trends in protection relays and 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 measures and systems accomplished to establish a reliable power supply network system are reported. 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 of introducing distributed generation into the distribution networks.