城市轨道交通对电力变压器的磁耦合机理研究OA

Existing research on the impact of metro systems on surrounding power transformers mainly focuses on DC bias in transformers caused by stray currents invading the transformer grounding grid,known as ground coupling.However,field measurements show that after installing protective devices on transformers,DC bias occurs in more distant substations,indicating that the mechanism of metro impact on surrounding power transformers is not the only mechanism.In this study,the proportion of transformer neutral point current components was analyzed.A CDEGS simulation model was established to investigate the potential distribution of the substation grounding grid under multi-train operation,and the line-induced voltage components were calculated using theoretical formulas.The results showed that the DC component in the substation grounding grid potential accounted for 64.25%,while the DC component of the induced voltage accounted for only 0.81%.Frequency-domain analysis of the measured transformer neutral point current revealed that the DC component accounted for 40.51%,whereas the DC component in the induced voltage was 9.13%.Based on these findings,a new source of bias current in transformers surrounding metro systems—magnetic coupling—was proposed.A method to analyze the components of transformer neutral point current was proposed.Using this method,it was calculated that in the measured transformer neutral point current,78.24%of the current was due to ground coupling,and 21.76%was due to magnetic coupling.This demonstrated the roles of both ground coupling and magnetic coupling mechanisms in transformer DC bias.The transformer neutral point current is mainly influenced by DC stray currents,with electromagnetically induced currents also contributing to a certain extent.This study provides a theoretical basis and methodological reference for the mitigation of DC bias in transformers.