 Protection coordination in DOCR  Application of FCL mechanism in power systems  Adaptive protection in power systems In this paper, the Directional Over Current Relay (DOCR) coordination with high constraints, which is an important problem in power systems engineering, is discussed. The classical object function reported in the literature has been modified to ensure optimum coordination of DOCRs. For the optimum coordination of the DOCR problem, Evaporation Rate Controlled Water Cycle Algorithm (ER-WCA) and Harris Hawk Optimization (HHO) algorithm are applied to modified object function. The proposed method is applied to the 9-bus test system. The results are compared with the literature. Results:The relay operation time is computed by HHO, and ER-WCA using proposed object function. Optimum values obtained by HHO was better than most of the algorithms presented in the literature. Then, successful application of FCL was presented. Conclusion:One can conclude from results of the paper that the HHO algorithm and proposed object function produces satisfactory results in DOCRs coordination problem. On the other hand, FCL mechanism may yield successful result in adaptive protection of power systems.