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Research and protection of stray current in grounding system of HV XLPE cable along subway

In the DC traction power supply system, because the running rail is used as a return path, it cannot be completely insulated from the ground, causing part of the current to leak and form a stray current. Affected by stray currents, stray currents also appear in the metal sheaths of high-voltage cables laid along the subway, which cause corrosion to the metal sheaths, resulting in an increase in the contact resistance between the insulating shielding layer and the metal sheaths. When there is an air gap between the metal protective layer and the insulating shielding layer, the internal field strength of the air gap exceeds the breakdown field strength under the impact of over voltage, resulting in discharge ablation, and even in severe cases, insulation breakdown and power failure accident. By modeling the composition and operation mode of the DC traction power supply system, simulating the distribution of stray currents, analyzing the causes of insulation breakdown, and on this basis, proposes a stray current protection plan for high-voltage cables near the subway.