Impact of Time Multiplier Setting Range on Optimum Coordination of Directional Overcurrent Relays

Abstract

Over-current relays especially Inverse Definite Minimum Time (IDMT) relays are most commonly used protective device in the distribution system. It is vital that during abnormalities or faults, the IDMT relays must be capable to isolate only the faulty part of power system from the healthy system. The operating time of IDMT relays can be reduced with proper coordination between primary and backup relays by selecting optimum settings. Heuristic-based optimization techniques are used to find the optimum solution for time multiplier setting (TMS) and plug setting (PS) of IDMT relays. In this paper, investigations are carried out to explore the impact of TMS range selected in the optimization problem on optimum settings of IDMT relays. The results of these investigations have shown that better results can be obtained with a minimum range of TMS. Three case studies are presented to show the impact of TMS range on optimum relay settings.

Keywords: Relay coordination, IDMT relay, TLBO, MATLAB