Reducing over-current relays operating times in adaptive protection of distribution networks considering dg penetration

The interest on distributed generations in smart distribution systems changed them to the integral part of the distribution networks. However, hosting of the distributed generation cause some problems for the distribution network protection system including performance delaying of traditional protection systems in case of islanding conditions which is because of the decreasing the sensed currents by the relays and false trip of the relays because of missing distributed generations. In this paper, due to overcome on these problems by using of adaptive relays, a protection scheme based on local data and offline calculation will be proposed which will help relays to adapt themselves with new situations and change their settings automatically and cause better performance in fault situations. In addition, these relays have the ability of fault detection and subsequently update their settings in both retrieval-islanded part by the distributed generations and the part, which are connected to the network. This protection scheme added to a test system and then the results comprised with the traditional scheme.