Research On The Impact Of Distributed Generation On The Protection Of Distribution Network

In recent years, the distributed generation has received widespread attention as a reliable, efficient and economic way to produce electricity. Combined with power grid, distributed generation is regarded as the main way to save energy and investment, reduce the loss, improve flexibility and reliability of power system by experts. Research and application of distributed generation has brought energy and challenge. Most of the traditional distribution network is single power supplied with the radial structure, the protection setting is based on this design. When distributed generation accesses to distribution network, the network structure, the power flow and short-circuit current changes, which will also affect the normal operation of the protection.Firstly, introducing the principle of three-section current protection of the distribution network, co-operation of automatic reclosing and protection. Research on definitions, classifications, characteristics and connection mode of the distributed generation is done, the simulation model of connection is established. Analyzing the affection on protection and reclosing by access points and capacity of distributed generation, distribution network changes from single power supply into multi-power system with the change of distribution and size of the short-circuit current, which leads to the rejection or misoperation of protection and reclosing. Power grid fails, there may be the formation of non-plan island.Secondly, analyzing the way to calculate short-circuit current with distributed generation, from the protection coordination point of view, taking series reactor and limiting capacity to eliminate the protection coordination with distributed generation. When short circuit happens, the reactance with high-impedance can limit the short circuit current supplied by distributed generation. Penetration level model distributed generation is builded with the constraints which does not affect the normal action of protection when there is line fault. The research on penetration level and its affection on protection by single and multiple distributed generation is done, and example proves the effectiveness of the above methods.Finally, the methods installing directional elements, setting value and taking the differential protection can improve existed distribution network protection.