Comparison of Transient and Power Frequency-Induced Voltages on a Pipeline Parallel to an Overhead Transmission Line

An analysis of the voltages induced on a 1-km pipeline by a parallel overhead transmission line has been carried out when the transmission line is carrying power frequency (50 Hz) current and when it is subject to the propagation of a lightning or switching transient. A frequency-based circuit modeling technique coupled with forward and inverse Fourier transforms is used to carry out this analysis. The relative severity of the induced voltages from power frequency current or transient (lightning/switching) overvoltages is illustrated using the simulation results. The results demonstrate the high relative magnitude of induced pipeline voltages that result from the propagation of lightning transients down overhead lines. The need to model the full overhead line for such an analysis is investigated as is the variation of the level of transmission line/pipeline coupling as a function of the local soil resistivity. Analysis of the level of induced voltage as a function of length of parallelism is also carried out.