Coordination of phase and ground DOCR using non-conventional time curves

This paper presents the coordination of phase and ground directional overcurrent relays in meshed networks. The protection of lines is performed considering positive, negative and zero sequence relays, for phase and ground fault detection. In phase protection, the settings and coordination of positive and negative sequence relays are evaluated. For ground protection, the performance of zero sequence relays under unbalance conditions are analyzed. The comparison between conventional and non-conventional time curves for the protection of meshed networks is performed, as well as its impact on the coordination results. The results from test system show that the use of non-conventional curves results in better relay coordination, getting lower relay operation times and reducing the number of violations.