Pipelines subject to induced AC voltages in common corridors with electric power lines often require the installation of an AC voltage mitigation system to reduce voltages to an acceptable level. Mitigation schemes include a grounding system (or systems) and often use solid-state decoupling devices connected between the pipeline and the grounding system to provide AC continuity, while maintaining DC isolation, so as not to affect the integrity of the cathodic protection system. However, various misconceptions about the characteristics of the decouplers, and their relationship to the grounding 'systems and pipeline, have at times resulted in confusion over how to apply and rate the products and associated equipment. Additionally, codes relating to installations are often violated due to unfamiliarity with proper methods, products, and good engineering practice. Misconceptions often include: decoupler AC vs. DC characteristics, voltage threshold considerations, AC fault current vs. lightning current ratings, conductor sizing, system response to induced AC voltage, classification of equipment for hazardous locations, and electrical codes governing installations. Each of these topics is reviewed in detail, relative to the application of products and systems involved with AC mitigation.
Keywords: decoupler, mitigation, grounding, threshold, classified area, induction