COMMON MISCONCEPTIONS REGARDING DECOUPLED GROUNDING SYSTEMS WHENMITIGATING INDUCED AC VOLTAGES ON PIPELINES

摘要

Pipelines subject to induced AC voltages in common corridors with electric power lines oftenrequire 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 decouplingdevices connected between the pipeline and the grounding system to provide AC continuity, whilemaintaining 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 thegrounding 'systems and pipeline, have at times resulted in confusion over how to apply and rate theproducts and associated equipment. Additionally, codes relating to installations are often violated due tounfamiliarity with proper methods, products, and good engineering practice. Misconceptions ofteninclude: decoupler AC vs. DC characteristics, voltage threshold considerations, AC fault current vs.Lightning current ratings, conductor sizing, system response to induced AC voltage, classification ofequipment for hazardous locations, and electrical codes governing installations. Each of these topics isreviewed in detail, relative to the application of products and systems involved with AC mitigation.