Distribution System Protective Device Coordination in Presence of Distributed Generation

Protection schemes in distribution systems have traditionally been designed assuming the system to be radial, characterized by a single source feeding a network of downstream feeders. After connecting distributed generation (DG), part of the system may no longer be radial, which means the coordination might not hold. This paper explores the effect of DG on protective device coordination, such as fuse-fuse, relay-relay, and fuse-relay. In each case, potential problems in conventional device coordination are identified and a solution is suggested. An actual system is analyzed to illustrate these problems and solutions.