Comparative study of heuristic algorithms for coordination of industrial over current relays with nonstandard characteristics in microgrid protection

The traditional methods for over-current relay coordination (OCR) may not be adequate to ensure consistent and dependable operation of microgrid (MG), in its various operating modes. In this work, optimal TMS settings for OCRs in a microgrid model have been obtained using SCA & mod WOA. OCRs with non-standard characteristics have been used as it is less investigated in literature. The results obtained are compared with those in standard literature using GA. It is found that the total time of operation (t_op) of relays reduces to 5.1676 s for operating mode 1(OM1), for operating mode 2 (OM2) t_op value reduces to 14.8376 s and the t_op reduces to 13.9448 s for operating mode 3 (OM3) by using SCA as compared to the values in standard literature considered here. The top of all individual relays in all the OMs is reduced in case of SCA as compared to the standard literature. At the same time the CTI for all relay pairs is maintained greater than 0.3 s, which is essential for relay coordination. The results using mod WOA are not satisfactory as far as the reduction in t_op is concerned for various operating modes, though the OCR coordination is achieved. SCA & mod WOA coding in MATLAB is used to optimize time multiplying setting (TMS) for OCR coordination. The International Electrotechnical Commission (IEC) microgrid benchmark system is implemented in DIgSILENT Powerfactory 2018 software to investigate the various operating modes of microgrid.