Mitigation of DOCR miscoordination through distance relays and non-standard overcurrent curves

This article presents the application of non-standardized inverse-time curves and distance relays to solve the lack of sensitivity of relays during overcurrent relay coordination. The inclusion of distance relays to replace the insensitive overcurrent is proposed, the effect of underreaching by infeed is considered. Directional overcurrent relays very frequently act as backup protection in sub-transmition networks when line differential relays or pilot protection are used as primary protection. Thus, the directional overcurrent relays (DOCR) coordination application should be evaluated not only in small electrical systems but also in large and meshed networks. The model used of overcurrent relay considers five adjustable settings to enhance the coordination when distance relays are considered. The proposed method reduces the number of relays that do not coordinate, this allows to obtain results with better implementation. The results show a performance improvement in overcurrent relay coordination in several highly interconnected IEEE systems.