Optimal coordination of overcurrent relays in radial system with distributed generation using modified firefly algorithm

Overcurrent relays (OCRs) play a vital role in operating the protection of power distribution system. In the presence of distributed generation (DG), OCR coordination is used to ensure reliability and speed of relay operation to avoid unintentional DG disconnection during fault conditions. Therefore, this paper presents an optimal OCR coordination in radial system under the presence of DG. An optimal OCR coordination can be obtained by selecting time dial setting (TDS) and plug setting (PS). A modified firefly algorithm (MFA) is proposed to finds the optimal OCR coordination. The proposed method is applied to four different case studies with DG. The proposed method is compared to both the firefly algorithm (FA) and conventional method. The results show that the proposed method can significantly improve the result of the FA and reduce all cases operating time of the OCR coordination, which reaches 38.38 %.