Effects of different earthing schemes on the stray current in rail transit systems

Running rails are used as return path for ^{DC electrified rail transit systems}. The resultant rail voltage causes stray current returning to the source via other paths such as metallic infrastructures. Stray current is the main reason of corrosion in the metallic parts which are located in the proximity of the railway. Many efforts have been made for controlling and reducing stray current. This paper discusses possible solutions for reducing stray current in Tehran Metro Line 3. Floating, diode earthed and solidly earthed schemes are various schemes for controlling stray current which are investigated here. Comparison of the rail voltage and stray current level for the mentioned schemes is presented. Also the stray charge and corrosive stray charge are investigated for Line 3. Finally multi train simulation study has been used to propose the best scheme for line 3.