A New Adaptive Method for Protection of Distribution System with High Penetration of Distributed Generations

The rapid growth of distributed generations (DG) in distribution grids brings new challenges in the protection coordination of overcurrent relays. So far, various adaptive techniques have been addressed to solve DG units’ mis-coordination problem, however, the un-predictable penetration of installed DG units highlights the importance of a penetration-free methodology. This study presents a novel offline, quick, applicable and cheap solution which guarantees protection coordination for any penetration and location of DG units. To do so, first, under different DG penetration levels and locations, the conventional protection performance is studied to discover the worst mis-coordination cases. Next, according to relays standards, the characteristic curve of the back-up relay is modified such that it can maintain coordination in all worst cases. The proposed methodology is applied to a power distribution network equipped with numerous DG units. The results successfully prove the effectiveness of the proposed method. This fact makes this method an attractive option for distribution systems with DG units.