Phasing Optimization as a Mitigation Strategy for AC Interference on Collocated Pipelines

Abstract High-voltage transmission lines constructed near buried pipelines can induce alternating current (AC) interference, posing safety and integrity risks under both steady-state and fault conditions. This paper highlights the application of transmission line phasing optimization as a practical strategy to mitigate AC interference and minimize the need for additional physical mitigation measures. A proposed 230 kV dual-circuit transmission line collocated with multiple natural gas pipelines was assessed using detailed modeling. Field data, including soil resistivity and pipeline facility surveys, were incorporated to evaluate induced voltages, and AC current densities. Various phasing configurations were analyzed to determine the arrangement that minimized inductive coupling between the transmission line and pipelines. Results demonstrated that optimal phasing was an effective method for lowering induced voltages and AC corrosion risks under steady-state conditions, substantially reducing the scope of AC mitigation required. This approach offers a practical and cost-efficient strategy for managing AC interference in pipeline corridors during the construction of new powerlines.