Protection Coordination of Distribution Systems Equipped with Distributed Generations

Coordination among protective devices in distribution systems will be affected by adding distributed generators (DGs) to the existing network. That is attributed to the changes in power flow directions and fault currents magnitudes and directions due to the insertion of DG units in the distribution system, which may cause mis-coordination between protection devices. This paper presents an approach to overcome the impacts of DG units insertion on the protection system and to avoid the mis-coordination problem. The proposed approach depends on activating the directional protection feature which is available in most types of modern microprocessor-based reclosers. This will be accompanied by an updating of relays and reclosers settings to achieve the correct coordination. It's clear that this approach do not need any extra costs or any extra equipment to be installed in the distribution system. An existing 11 kV feeder, simulated on ETAP package, is used to prove the suitability and effectiveness of the proposed approach. The results ensure the possibility of achieving the proper coordination between protective devices after inserting DG units if the proper and suitable settings of these devices are realized.