A theory and design of an insulating insert in a cathodically protected underground water pipeline. I. Currents and potentials at the inner pipe-face and the insert's total resistance

Equations of the potential and current distribution over the inner face of a pipe near an insulated insert, as well as the insert's total resistance, are derived. It is shown that the contribution of the anodic and cathodic zones adjacent to the insert to its total resistance is noticeable and can be higher than that of the water column in the insert itself.