Active stray current protection systems in DC railways

Electrified transport systems generally use running rails as a neutral conductor. Due to the fact that perfect electrical insulation in the rails does not exist, traction current flows out of the electrical circuit into the soil, finds the path of least resistance and returns back to the substation.The path of the stray current can pass through the soil itself, the pipes and cables of the utility sector laid in the ground, or other metal structures such as bridges. If an alternative path with less resistance appears, a proportionally larger part of the stray current will pass through it.Stray currents cause corrosion on the surface of the conductor, the rail where it flows. Buildings along the section, steel bridges and reinforced steel driven into the ground, are also in danger. It follows that many companies have an interest in controlling and eliminating traction current leakage and reducing the damage it causes.This report discusses types and efficiency of active stray current protection in DC railway systems.