Investigation of The DGs Effect on The Coordination Between Protective Elements in Distribution Network 120 57

Abstract

Addition of Distributed Generators (DGs) to the electric network have more advantages to the network. It improves the voltage profile and the power flow in the network. In the last decade, DGs is used in power system, especially the distribution system. Coordination study for protective devices must be performed on the distribution network with DGs to reach selectivity with minimum clearance time of fault. Due to DG insertion to the electric system, the short circuit level is changed and coordination between protective elements should be done. This paper presents a technique to avoid the miscoordination problem between protective devices due to the impact of DG units insertion without any additional costs. The proposed technique depend on activating and updating the setting of network relays to achieve correct coordination. Also, it doesn't need any additional costs or any additional equipement to be installed in the electric network. This paper make studies on a real radial system of power transformer with its feeders of a 66kV utility substation before and after adding DGs. ETAP software is used to simulate the network under study.