The Co-Ordination and Testing of Protective Relays in Industrial Plants

This paper is concerned with the co-ordination and the maintenance of protective relays, as found in the widely dispersed industrial plants of one large chemical corporation. Co-ordination and relay maintenance conducted by engineers from a single central agency has proved technically and economically justified. While problems involving co-ordination and shortcircuit studies are discussed in this paper, they serve only to illustrate the effectiveness of a centralized operation. (Treatises on these subjects, which have proved to be useful, are listed as references 1-11.) The related problems of voltage dips during faults, short-circuit current-carrying capacity of conductors, momentary duty of devices, and interrupting capacity of fuses and breakers are considered as a part of the co-ordination problem. This paper further discusses the differences in emphasis placed on some problems by the utility and the industrial plant.