Calculation of Interference Voltage on the Nearby Underground Metal Pipeline due to the Grounding Fault on Overhead Transmission Lines

Electromagnetic interference on the underground metal pipelines in parallel with the faulted power transmission lines includes two parts: inductive and resistive coupling. Based on the multiconductor transmission line model consisting of overhead power lines and underground pipeline, the tower grounding resistance is, respectively, modeled by the lumped-parameter processing and distributed-parameter equivalent method. Then, the formulas of voltages and currents along the transmission lines are derived combined with the constraints of voltages and currents at the transmission line´s ends and the location of grounding fault. Regarding the earth-fault currents along the towers as the excitations, the method of moment is used to investigate the resistive coupling voltage on the nearby underground metal pipeline. Compared with the results of commercial software CDEGS employing the electromagnetic field analysis, the proposed method is proved to be correct and effective. The simulations also show that the results by the lumped-parameter processing method are more accurate than those by the distributed-parameter equivalent method during the tower grounding resistance modeling. Finally, the proposed method is applied to investigate the influence of parallelism length, separation distance, soil resistivity, tower grounding resistance, insulation coating resistivity, grounding fault location, and fault currents from the substations on the pipeline´s coating stress voltage.