Induced voltages and currents on gas pipelines with imperfect coatings due to faults in a nearby transmission line

An improved hybrid method is discussed, employing a finite-element method along with Faraday's law and standard circuit analysis, in order to predict the induced voltages and currents on a pipeline with defects on its coating, running parallel to a faulted line and remote earth. Such defects are a frequent situation especially when old pipelines are considered and are modeled as resistances, called leakage resistances. The fault is assumed to be outside the parallel exposure so that conductive interference is negligible and therefore the problem is a two-dimensional one. Input data are power line and pipeline configuration, physical characteristics of conductors and pipeline, fault and power system terminal parameters and location and value of leakage resistances. Simulation results show that for small values of leakage resistances, defects act as a mitigation method for the induced voltages on the pipeline. However, in that case large currents that flow to earth through the defects can damage the pipeline.