Adaptive modified firefly algorithm for optimal coordination of overcurrent relays

One major concern in using over current relays (OCRs) is their coordination in power system protection to decrease the pressure of electrical equipment and avoid mal-trip in the primary and backup relays. The issue has recently become more challenging with the increasing use of distributed generation (DG). This study proposes the use of firefly algorithm (FA) to achieve an optimised coordination of OCRs in power system protection when DG is present in the system. Typically, the FA is done by selecting plug setting and time setting multiplier parameters. However, the algorithm associated with such method requires a long convergence time and has the risk of getting trapped in local optima. Therefore, an adaptive modified FA (AMFA) has been developed to overcome these issues and obtain the optimised coordination of OCRs. The AMFA is tested in five case studies of a power system with DG whose results are then compared with those obtained from the conventional and FA methods. The results demonstrate that the proposed AMFA is able to achieve the optimised coordination of OCRs in all test cases with significant improvement in time reduction reaching 40.446%.