An adaptive over-current protection scheme for MV distribution networks including DG

Conventional 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 in a network, leads to losing coordination of protection devices. Therefore, it is required to have an algorithm in hand which is capable of protecting distribution systems that include DG, through diagnosis and isolation of occurred faults. In this paper, a new approach for protecting of distribution networks in presence of DGs will be presented. The algorithm is based on dividing an existing distribution network into several zones; each of them is capable of operating in island operation. The proposed scheme has been implemented on some part of a real distribution network and performance of the proposed scheme is tested on it. For simulating the sample network and for implementing the relay algorithm, DIgSILENT Power Factory and MATLAB are used respectively.