THE STATE-OF-THE-ART OF NUMERICAL RELAYING

The present state of the art of numerical relaying (commonly known as computer relaying) and its expected advantages, is outlined. This paper commences with a brief overview of computer and microprocessor-based relaying developments. Computers have brought two developments to protective relaying: more sophisticated traditional relaying, and the ability to adapt the protective system to changing system conditions. Numerical relays have already been put into operation at several utilities and they have contributed greatly to the improvement of power supply reliability. Typical examples of the developed equipment are described. Owing to the introduction of numerical techniques, the coordination of protection and station control systems has been an important issue during the recent years. Finally, expected trends in the area of algorithm and communication development which permit the development of a concept of adaptive relaying and coordinated protection and control for power system network are briefly mentioned.