Design and Testing of a Microprocessor-Based Distance Relay

This paper describes the design and testing of a digital distance relay for high voltage systems. It shows how a prototype has been built using two single board computers in a multiprocessor configuration. This design allows simultaneous real-time filtering of the voltage and current signals and computation of the apparent impedances "in parallel". The paper presents the results of the tests carried out on a prototype of the relay using a transient signal generator test circuit. A trip signal is produced by the relay in less than one 60 Hz cycle after fault occurrence for all faults.