Research on Stray Current Suppression Method for Establishing Separate Grounding Grid of Cables

The invasion of stray current from DC metro systems into the power grid substation through cable armoring will cause transformer DC bias magnetism and affect the normal operation of power grid. Therefore, in order to suppress the value of DC metro systems stray current invading the power grid through cable armor, this paper proposes the suppression method of establishment of a separate grounding grid of cable armor. Firstly, this paper establishes the coupling model of DC metro systems and the nearby power grid considering the metal and soil structure by using the CDEGS software. Secondly, this paper researches the influence of separate grounding grid and soil parameters on the stray current. Finally, the results show that the establishment of a cable armored separate grounding grid will reduce the neutral current of the line armored and the transformer at both ends, and will have almost no effect on the stray currents in the rest of the transmission lines and transformers in the power grid. The distance of the separate grounding grid from the substation has a small influence on the stray current suppression effect. The greater the resistance of the separate grounding grid, the more obvious the effect of suppressing stray currents. The soil resistivity has an obvious effect on the suppression of stray currents. Therefore, the use of separate cable grounding grids can be adopted in the future to reduce the impact of stray currents on the power grid.