Study on line protection of distribution network with DFIG based on current decay factor

Because of the high permeability integration of the dispersed wind power to the distribution network, the fault current direction, amplitude and phase angle have significant changes, and it is difficult for the traditional three-current protection to adapt these changes. The transient characteristics of the wind turbine are not the same as the system power, leading to the protection scheme can't adapt to such characteristics. By theoretical derivation the transient characteristics of the doubly-fed induction wind generator (DFIG), the decay characteristics of DFIG is got in this paper. According to the analysis, a line protection scheme based on the current decay factor difference is proposed. The fault region is identified by the difference of the current decay factor between the two ends of the fault line. Referring to the parameters of the first exemplary project in which the dispersed wind power is integrated into the 10kV local power grid. The active distribution network simulation model is built in PSCAD/EMTDC, the simulation results show that the proposed scheme can operate correctly with different fault type, fault position and wind field output, and it can adapt to various operating conditions sensitively and effectively.