Research on the Protection Scheme of DG Interconnection Transition Mode Based on Decoupling Zero Sequence

Abstract

More and more DG is connected with the grid through the low voltage distribution network, how to choose a protection scheme without depending on the nature of DG, and with reliable operation mode is a big issue encountered by the engineers. The rationally allocating the protection scheme of grid connection coupling point, which not only can judge the system fault in time, and judge it in DG island, and can still remain the protection features in the dynamic process of the island formation and in the operation mode of dividing island, can always have enough selectivity of the island fault is the problem to solve in this study. Through the selection of the grounding methods of DG grid connection transformer, the relationship between zero sequence current and zero sequence voltage is analyzed; the optimization of the protection scheme can inhibit DG interconnection and zero sequence over-voltage in network running-off, and quantity of zero sequence can be used as a stable criterion when the fault occurs, so as to work out a set of protection optimization schemes for DG interconnection transformer grounding system. Finally, through the COBASE system, a protection scheme of the wind power plant low-voltage grid is generated in this study, which verifies its excellent protection features in the DG connected to the grid system.