Abstract
Alternating Current (AC) interference affects pipelines collocated near high voltage transmission lines. While overhead high voltage transmission line collocations are common, underground high voltage transmission line collocations, while less common, can cause similar interference effects on pipelines. This paper describes the feasibility evaluation of a proposed 35 km underground transmission line route in the United Kingdom affecting a nearby pipeline. The proposed transmission line was to consist of either three 220 kV circuits or six 132 kV circuits; both cases were evaluated. The proposed transmission line phase cables were to be installed with concentric sheath conductors, direct buried in a close trefoil configuration, and bonded to underground splice boxes at various locations. In addition to the proposed transmission line route, the project evaluated a set of base cases: a typical pipeline paralleling at varying offsets for various lengths under a variety of operating conditions and a typical pipeline crossing scenario. The effect of soil resistivity on the interference levels experienced by the pipeline was considered. The feasibility study assessed the expected steady state, fault state, and AC corrosion effects that the proposed transmission line could have on any nearby pipelines. Results for all cases and scenarios will be discussed.
