Design and application of a stray current monitoring system

The reason and character of stray current from DC electric traction systems and its influence upon buried pipe were briefly introduced in the paper. The traditional measurements and monitoring methods in subway for stray current were discussed. A new system for monitoring the stray current, based upon virtual instrument, was put forward. The proposed system has some advantages such as automatic and continuous monitoring of stray current. The pipe-soil potentials of a gas pipeline, located in the neighboring area and parallel to the rail transit powered by a DC source in Shanghai, were tested by means of proposed system. The actual results prove the feasibility of the system.