Interactive power system simulation for the laboratory evaluation of power system protection relays

Attention has been focused on developing improved methods for evaluating the performance of modern protective relays, and in particular, relays used for EHV transmission line protection. The techniques described by the authors are based on digital power system simulation and extend the concepts of the programmable transmission line (PTL). In such a system, data generated by simulation programs is transformed into real-time current and voltage signals, which, after amplification provide the relay under test with input signals similar to those which it would encounter under fault conditions while in service. The authors describe the implementation of the PTL technique using a widely available desk-top microcomputer and the development of new features which enable the relay's response to both fault and post trip conditions to be examined. System operation is illustrated using tests which model the difficult operating conditions associated with a particularly onerous power system configuration.