Abstract
Distributed-source transmission line theory is used to model the electrical response of a pipeline to telluric currents. This modelling shows that the effect of telluric currents depends on whether the pipeline is long or short in relation to a telluric current adjustment distance determined from the resistance along the pipeline and through the coating to ground. Observations from an “electrically long” and an “electrically short” pipeline are presented and demonstrate the validity of the model calculations. On the “electrically long” pipeline the maximum voltage is independent of pipeline length and inserting an insulating flange just creates an additional site where large potential variations are produced. In contrast, the maximum voltages produced on an “electrically short” pipeline are proportional to pipeline length so splitting the pipeline in half with an insulating flange reduces the maximum potentials by half.
