Protection of distribution systems with significant penetration of distributed generation

With increase of distributed generators (DG) in power system, there arise the potential for operation of power system during islanding mode as well. Along with its advantages, there come challenges with protection system due to change in short circuit current (which is the primary factor for overcurrent relay setting). In this paper, investigation of impact of Distributed Generators (DG) in protection system of the distribution network has been carried out. Simulation based study regarding protection issue during islanding condition has been carried out for distribution network in mid Himmerland (Denmark). Use of definite time overcurrent relay along with directional overcurrent relays has been proposed for the reliable protection scheme. Simulation in `DIgSILENT Power Factory´ shows the proper selectivity and coordination of overcurrent relays for 3 phase faults during various cases, such as islanding or shutdown of some DG.