Protection of Distributed Generation (DG) interconnection

Selection of the DG interconnection protective relay is based on several criteria such as power system characteristics, the dynamic response of the generator, the system grounding, the DG transformer connection, etc., as well as the protection policy of the utility and coordination requirements. The interconnection protection IED design can be summarized as follows: Disconnection of DG plants when no longer operating in parallel with the utility grid; Protection of the utility grid from damage caused by connection of the DG plants (voltage transients, fault current supplied by DG, reclosing without check sync, etc.); Protection of the DG plant from damage caused by the utility grid; Coordination with other protective relays should be made to prevent unnecessary trips; Possible implications on utility protections must be analysed when a DG is connected, depending on the characteristics of the network, such as the loss of coordination or sensitivity, reclosing co-ordination, etc.