Abstract :
THE RAPID GROWTH in the utilization of electric energy and the importance of continuity of service has increased the application of protective relays. This magnifies the problems of space, which is already at a premium in many existing stations and an increasingly costly item in new stations. A critical examination indicated that considerable savings in space could be effected in many of the relay designs and still improve accessibility to the relay operating units. Consequently, a major redesign program was undertaken to provide these advantages and also to incorporate many other technical improvements. Along with the concept of reduced size, other important concepts were given renewed emphasis in this redesign program. These were (1) designs built around a minimum number of standard basic units, (2) self-containing each relay type within the relay housing, (3) unit designs of self-aligning parts, (4) minimum adjustments, and (5) designs for universal application to reduce varieties. These concepts form the basic design philosophies underlying the new lines of relay cases: the induction-time overcurrent, directional-time overcurrent, and induction-time voltage relays described in this article. The results are compact modern protective relays of reliable performance and minimum maintenance.
