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The calculation formula for divergence of DC grounding current was put forward. The divergence of DC grounding current at different directions in the earth was studied. The main factors include the pattern of electrode, distance between sending end area and receiving end area, earth structure, etc. Some important conclusions were discovered. When observation point is close to DC grounding electrode, the pattern electrode has a big effect on the divergence of DC grounding current. When observation point is far from DC grounding electrode, soil structure has an effect on the divergence of DC grounding current. When the distance between DC grounding electrodes in the sending end area and receiving end area is short, the interaction of two electrodes should be considered.

DC magnetic biasing problem,caused by the DC grounding electrode, threatened the safe operation of AC power grid. In this paper, the characteristics of the soil stratification near DC grounding electrode was researched. The AC-DC interconnected large-scale system model under the monopole operation mode was established. The earth surface potential and DC current distribution in various stations under the different surface thickness was calculated. Some useful conclusions are drawn from the analyzed results.