Analysis Of The Influence Of DC Bias On Transformer In Zhejiang

At present,the "west to East,North South mutual supply,national network",the development of large capacity long-distance transmission is the general trend of the development of power grid in china.Power grid interconnection,the use of direct current transmission,it is conducive to improve the stability of the power grid.DC power transmission project China yijianhuzaijian reached ten,is expected in the future,long-distance large-scale hydropower project will send most of the DC transmission.HVDC system monopole operation in the earth as the circuit of main transformer neutral point around the substation grounding system is direct current DC bias caused by.Transformer DC bias will reduce the efficiency of the transformer,shorten the life of the transformer.This paper introduces the definition and characteristics of the DC bias,and discusses the method to suppress the DC bias.In this paper,the main variants of Zhejiang province are analyzed,and the tolerance of different types of transformers to DC bias is briefly analyzed.Through numerical calculation method in this paper,Zhejiang HVDC grounding near 500 k V substation modeling,changes in the surrounding potential distribution of grounding current caused by Zhejiang converter was calculated,analyzed the different soil resistivity model on the potential distribution of the HVDC system monopole operation calculation,main transformer neutral DC current through the substation,and the neutral system blocking schemes are analyzed.In the end,the paper discusses the feasibility and the implementation method of the DC bias suppression device.