Designing a new protection system for distribution networks including DG

Traditional electric distribution systems are radial in nature, and are supplied through a main source. These networks have a very simple protection system which is usually implemented using fuses, reclosers, and over-current relays. Recently, great attention has been paid to applying Distributed Generation (DG) throughout electric distribution systems. Presence of such generation units leads to losing coordination of protection devices. Therefore, it is required to have an algorithm in hand which is capable of protecting distribution systems including DG, through diagnosis and isolation of occurred faults. In this paper, a novel approach to protect distribution networks in presence of DG will be presented. The algorithm is based on dividing an existing distribution network into several zones which each of them is capable of operating in islanding mode. Also the proposed scheme has been implemented on a sample distribution network using DIgSILENT and MATLAB and its performance has been tested.