AC Mitigation and Cathodic Protection for a Long Regulated Pipeline

This paper highlights the coordinated AC mitigation and cathodic protection strategy for a 167-mile long high-pressure interstate natural gas pipeline.  Ninety-five percent of the pipeline is located adjacent and parallel to high voltage AC power transmission lines ranging to 500 kilovolts.  Analyses and computer simulations during the front-end engineering design predicted that, without suitable mitigation, steady-state AC potentials on the pipeline would easily exceed 100 volts; AC potentials approaching 12,000 volts were predicted during a power line to ground fault.  The AC mitigation and cathodic protection designs were closely coordinated with operations personnel to assure systems that were maintenance-friendly.  Corrosion control commissioning included a multi-channel AC and DC close interval potential survey protocol.  The baseline data document the success of the AC mitigation and cathodic protection in safely and cost effectively controlling soil corrosion and AC interference.   Long-term surveillance includes state-of-the-art remote monitoring and the use of coupon technology.