Inductive interference calculation on imperfect coated pipelines due to nearby faulted parallel transmission lines

The interference of power transmission lines to nearby pipelines and other metallic structures has been a research subject over the past 20 years. Especially during fault conditions, large currents and voltages are induced on the pipelines. Several methods have been proposed over the years and more recently one utilizing finite element calculations. The last method has the disadvantage that if it considers the pipeline to have a perfect coating, which is rarely the case as defects appear on the coating soon after the pipeline is buried in the ground. In this work a hybrid method employing finite element calculations along with Faraday's law and standard circuit analysis is discussed. The method is used in order to calculate the induced voltages and currents on a pipeline with defects, running in parallel to a faulted line and remote earth. Non-parallel exposures are converted to parallel ones and dealt with similarly. The defects are modeled as resistances, called leakage resistances. The fault is assumed to be a single earth-ground one and outside the exposure so that conductive interference is negligible. A sample case is analyzed and discussed. The results show that although the pipeline defects act in a way as to reduce the levels of induced voltages and currents, large currents can flow to earth through the defects that may damage the pipeline. (C) 2003 Elsevier Science B.V. All rights reserved.