Optimized neutral point connection mode configuration against DC Bias of 220 kV power transformation in Yichang power grid

The occurrence of DC Bias will affect the normal operation of power transformer, thus DC bias withstand capability of transformer is a prerequisite for stable operation of power system. In this paper, the DC current distribution model of transformer neutral point in Yichang area is established. Meanwhile, according to the transformer noise limit, the maximum current which is allowable to flow through transformer neutral point is determined. On this basis, an optimization of neutral point connection mode configuration is proposed to inhibit DC bias. Since the change of zero sequence impedance, at last we give sensitivity verification of zero sequence current protection base on the RelayCAC model of Yichang power grid. Simulation results show that the sensitivity meet the requirements and verify the effectiveness of the proposed method.