High Voltage Direct Current Interference With Underground/Underwater Pipelines

Underground/underwater pipelines are susceptible corrosion from DC stray current originating from the operation of HVDC transmission systems.  With increasing population growth and the demand for electrical power, HVDC transmission is an economical method of transporting electrical energy over long distances.  There are two distinct types of HVDC transmission, mono-polar and bipolar.  Mono polar systems use the earth or preferably sea water as the return circuit, whereas bipolar systems only use the earth or sea water during electrical upsets or faults.

This paper will outline the effect of stray current that originates from a HVDC transmission system that crosses a crude oil pipeline system.  Ground fault currents as high as 2300 amps have been recorded flowing through the ground when the bipolar HVDC system utilizes the earth return circuit during system upsets.