A hybrid improved harmony search algorithm-nonlinear programming approach for optimal coordination of directional overcurrent relays including characteristic selection

Abstract

The objective of optimal coordination of directional overcurrent relays (DOCRs) is to search optimal relay settings. This leads to the minimum operating time of relays for faults in their primary protection zone under the coordination and boundary constraints. In this paper, relay settings are considered as pairs of - pickup current setting (Ip) and time multiplier setting (TMS), plug setting (PS) and TMS - for solving the coordination problem on 8-bus and 15-bus networks. Moreover, a new hybrid improved harmony search algorithm-nonlinear programming (IHSA-NLP) approach is proposed to solve the relay coordination problem. To demonstrate the superiority of IHSA-NLP method, obtained results are compared with the IHSA and existing methods presented in the literature. Also, the effectiveness of the proposed method is evaluated with the coordination problem considering multiple characteristics on IEEE 30-bus network.