A Half Cycle Bus Differential Relay and its Application

The principles of a new high speed bus differential relay which operates for an internal fault condition within 1 to 2 ms and initiates tripping of circuit breakers in about 7 ms is described. The relay is self-powered and requires no auxiliary voltage other than that needed for the output tripping and alarm functions. It is shown to be insensitive to remanence and saturation of current transformers and to systems fault levels and X/R ratios.