Minimum Separation Distance Between Transmission Lines and Underground Pipelines for Inductive Interference Mitigation

A method to determine the minimum horizontal separation distance between transmission lines and underground pipelines for inductive electromagnetic interference mitigation under normal operation of transmission lines is proposed in this paper. The proposed method takes both AC corrosion of pipelines and a 15 V touch voltage safety limit into account. For a pipeline facility of Manitoba Hydro, soil resistivity is firstly measured at 20 locations near the pipeline; a soil model is then created for each location using the RESAP module in CDEGS software package. Two critical soil resistivity values for AC corrosion limit and 15 V voltage limit are selected for this pipeline facility. After the soil model is determined, the HIFREQ module in CDEGS is used to simulate the induced AC voltage, and a minimum separation distance can be recommended. Four voltage classes of transmission lines, 115 kV, 138 kV, 230 kV, and 500 kV, are considered. Two curves and their empirical models are created for each voltage class to determine the minimum separation distance. The modeling method is validated using two case studies with field measurements. The proposed method and guidelines can significantly improve the future line route selection process for new transmission lines.