Development of Digital System Technology Applied to Advanced Digital Relay

Abstract

A digital relay is always required its complete operation when fault of electric power system occurs, and not to cause any maloperation when power system is normal. Considering the complex phenomena of power system and easy operation and maintenance, it is needed to improve the performance of digital process, friendliness of human interface, distinction of troubled hardware, and flexibility to constitute the digital relay system.
In this paper, authors propose to realize them with high reliability that, (1) Human interface using display connects to main and failsafe relay individually, (2) Data exchange between CPU's of multi-cpu system must be message type with check mechanism, (3) Software of each CPU must be based on multi-task system with protective mechanism, (4) Graphic language is very useful to the reliability of software, and (5) Self check can point out the troubled card or input channel.