Geomagnetic effects on the pipe-to-soil potentials of a continental pipeline Original Research Article

Geomagnetic variations produce electric fields that drive currents in the earth and in man-made networks of conductors. These induced currents create differences in potential between pipelines and the surrounding soil which interfere with electrical surveys of the pipe and produce conditions where corrosion may occur. Distributed-source transmission line (DSTL) theory has been used to model the electrical reponse of a continental pipeline and expressions are derived for the pipe-to-soil potentials as a function of the electric field and the pipeline characteristics. The largest pipe-to-soil potentials are shown to occur at the ends of a pipeline, at pipeline bends, and at pipeline discontinuities such as junctions between pipes. Combining this information with statistics on geomagnetic activity provides a way to determine how often the pipe-to-soil potentials at these locations depart from the −850 to −1150 mV range for optimum cathodic protection.