A Prototype of Multiprocessor Based Distance Relay

Abstract

This paper concerns the design and realization of a digital relay for EHV systems. It describes the algorithm which has been used and the main principles of operation. Then it shows how a prototype has been built with four 16-bit microprocessors, to allow the simultaneous real-time computation of three apparent impedances. The hardware and software architecture are described. The paper also presents the results of the tests carried out on the relay: a tripping signal is sent within one period of 50 Hz for all faults (half a period for near-by short-circuits). Furthermore, single-phase tripping, directional discrimination and power-swing detection are provided.