Protection of distribution networks in presence of DG using Distribution Automation System capabilities

Using distributed generation (DG) is an interesting topic that has drawn attention of electrical engineers to itself in recent years. Presence of these generation units in distribution systems, although has many advantages and benefits, has to be applied after performing detailed studies and investigations due to their complexities in operation, control and protection of network. One of the most considerable problems that arises, when DGs are used, is destructing efficiency and qualification of the existing protection system. The injected currents of DGs to a distribution network lead to not having a radial network any more, and consequently cause the network faces an inefficient protection system that was formerly designed according to the existing philosophy behind the distribution network. In this paper, a new protection scheme has been presented to provide the distribution networks including DGs. The new approach, designed based on capabilities of distribution automation system (DAS), has been implemented using a computer-based relay which is installed in the sub-transmission substation. As case study, the proposed scheme has been assessed using a MATLAB based developed software on a real distribution network.