A research of feeder protection 10kV distribution neteorks including distributed generation

More and more distributed generation(DG)is being connected into distribution network with the development of power grid. The connection of DG will impact the feeder protection directly. It may lead to loss of protection´s selectivity or decrease of protection sensitiveness. More badly, the protection may refuse to act or act mistakenly. In this paper a practical distribution network with DG which exists in the power grid of SHINAN Power Supply Company is proposed. Based on this example grid, what impact the DG brings to the feeder protection and how it affects the feeder protection are studied deeply. An improved protection scheme is proposed considering the impact of DG. New protection scheme includes two major changes. Firstly directional unit is added to the feeder protection which may act mistakenly. Secondly, two sets of setting value are applied to some feeders´ protection and the protection can switch to one or the other setting value depending on whether DG is interconnected to the distributed network. An ATP model of the example distributed network is built and a large number of simulations are made which covers all fault situations which may occur in the network. The simulation result indicates the proposed protection scheme can meet all of the need in protection sensitiveness and selective ability. In summary, the new protection scheme can solve the problem that the connection of DG brought to distribution network´s feeder protection.