Determination of Allowable Capacity of Distributed Generation Units for the Prevention of Protection Mis-Coordination in Distribution Networks

In recent years, the advantages of applying Distributed Generation (DG) units have been analyzed in most of scientific discussions. Distributed generation rapidly alters the structure of the electric industry from monopoly to competitiveness and can completely change the structure of power networks in the 21st century. One of the main challenges that can be a demerit of the presence of distributed generation is altering the radial structure of distribution networks. Injection of DGs current to a distribution network results in losing radial configuration and consequently losing the existing coordination among protection devices as well as decreasing reliability of the network. This paper aims to propose a new method based on determination of allowable capacity of DGs at each node for the prevention of protection mis-coordination in distribution networks. This methodology is explained in two cases. In the first case, just one DG at each node is regarded, and in the second case, presence of two or more DGs in separate nodes is considered. Finally, the methodology is tested on a typical distribution feeder and the simulation results are presented and discussed.