Modeling of Stray Currents From Metro Intruding Into Power System Considering the Complex Geological Conditions in Modern Megacities

The risks of power supply in power systems attributed to stray currents caused by denser metro lines are increasing in modern megacities. Factors such as multi-layered soil and multiple metro operating lines (MOLs) make it more difficult to analyze dc coupling between the metro and power system. This article proposes a model for dc coupling of the metro and power system considering the two systems' spatial information, the actual multi-layered soil, and the non-linear ionization of soil caused by stray currents. This article presents a dc coupling model suitable for studying multiple metro lines and large-scale power systems in modern megacities, which has an average relative error of 6.3% compared with experimental results. The neutral current of the transformer in a substation is up to 43 A (normal operation requires it to be less than 6 A in amplitude) under the influence of multiple MOL. The non-linear ionization of the soil near the power substations' grounding network will decrease the soil resistance, this also results in greater dc currents intruding into power substations.