Stray current control by a new approach based on current monitoring on a potential probe

To control stray current interference due to DC transit systems, cathodic protection at the so-called constant potential condition is used. Pipeline potential is continuously measured by means of a fixed reference electrode, and the measured value is used to control dynamically the feeder in order to match the protection condition. An accurate analysis of this technique reveals that during interference what is maintained constant is the IR drop in soil rather than the true potential of the structure. A new approach was investigated: the innovation consists of the use of the current, rather than the potential, to control the feeder on the basis of an effective range of the current the probe should receive. Laboratory tests confirmed the feasibility of such an approach. Modelling and test results are presented and discussed.