The calculation of DC distribution in Hami AC power grid

The DC magnetic bias is caused by the grounding current of HVDC transmission project. In order to analyze the influence that the grounding current of Tian-Zhong HVDC transmission project brings to the present Hami AC power grid, this paper is based on the coupled field-circuit method and the power grid topology structure of Hami area, the DC current distribution model in the Hami area is built. The model is proved to be correct after proceeding simulations and experiments. According to affordable DC current of some typical transformers, the conclusion is that some transformers in Hami area have serious DC magnetic bias risk under the present operation condition. Based on the present operation condition some reasonable control methods are proposed.