The third type of ECP is an electric drainage protection that utilizes circulating current of railway electric transport as cathode current. Circulating current is a part of traction current of tramway or electric train.
The simplest electro drainage unit is a cable crosspiece between pipeline and rail track. Current value at the crosspiece should be defined by difference of pipe-rail track potentials at the point of contact. Circulating current shall perform its protective functions if the rail track potential is less than the pipeline potential. In this case the current will be directed from pipeline to the rail track by the crosspiece.
The third type of ECP is an electric drainage protection that utilizes circulating current of railway electric transport as cathode current. Circulating current is a part of traction current of tramway or electric train. 