Reducing Pipeline AC Interference by Phase Permutation

High-voltage power lines can induce alternating current (AC) voltages on nearby gas pipelines, creating safety and corrosion risks. This article presents a French case study involving three gas pipelines exposed to severe interference from a 225 kV dual-circuit line over 17 km (10.6 mi).A Initial simulations predicted voltages approaching 200 V in the steady state; nine earthing systems were installed to reduce them, but these were not sufficient to meet design criteria. A further study examined conductor arrangement and led to phase permutation on the power line. Field measurements confirmed a major mitigation effect, with voltage levels reduced by about a factor of four and AC current densities significantly lowered.