AC interference on pipelines in the nearby vicinity of HVAC transmission lines has become increasingly prevalent in industry as shared utility corridors have become more widespread. These AC interference levels, if severe enough, can present a shock hazard to anyone who may come into contact with exposed portions of the pipeline. Additionally, the integrity of the pipeline can be compromised as a result of accelerated AC corrosion and/or damage from a fault incident from nearby transmission line structures.
AC interference levels can be predicted using a number of different methods including various field measurements as well as detailed computer models. The accuracy of these computer models however, is highly dependent upon the reliability of the model input data, specifically the operating characteristics of the transmission line(s). Historically there has been limited cooperation between pipeline and power utilities with respect to AC interference studies, requiring many design assumptions which can lead to under protected systems, or overly conservative and inefficient mitigation designs.
This paper details an AC interference study initiated by a power operator, upgrading an existing transmission line from 115 kV to 230 kV. Field measurements were collected on the pipelines and compared to computer modeling results and known operating loads to validate a baseline model. Multiple tower configurations, operating loads, and transmission line routes were assessed in order to minimize the AC interference effects on the pipelines located in the shared utility corridor. The end results illustrate the benefits of not only assessing AC interference levels during the transmission line design and planning phase but also the importance of cooperation between utilities to enable the most efficient means of AC interference mitigation.
Key words: AC Interference, HVAC Transmission Lines, Electromagnetic Induction, AC Corrosion