Interference problems and solutions on the Tyneside DC Metro System

The author briefly discusses the electrical equipment of the Metro which is supplied by 1500 V DC overhead lines. The author discusses the problem of interference leading to corrosion of gas mains caused by leakage currents. The author discusses the earthing policy adopted and sources of interference. The tests to establish the effects of the leakage current are discussed and the solution to the problem described. This involved using remedial bonds to reduce potential swings at impedance bond points