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TitleAssessing pipeline vulnerability to telluric currents
AuthorBoteler, D H
SourceProceedings of CORROSION 2007; 2007 p. 1-16; 1 CD-ROM
Alt SeriesEarth Sciences Sector, Contribution Series 20100350
MeetingCORROSION 2007; Nashville; US; March 11-15, 2007
MediaCD-ROM; digital
Subjectsgeophysics; engineering geology; telluric interpretations; telluric surveys; telluric field; pipelines; modelling
ProgramTargeted Hazard Assessments in Northern Canada, Public Safety Geoscience
AbstractTelluric currents produce variations in pipe-to-soil potential (PSP) that take the pipeline outside the voltage range for cathodic protection and interfere with potential surveys. The size of the PSP variation depends on a variety of factors related both to the natural environment and the characteristics of the pipeline itself. This paper presents a methodology for assessing how different pipeline features influence the vulnerability of the pipeline to telluric effects. Derivation of the distributed-source transmission line (DSTL) equations for induction in a pipeline show that the critical parameters are the series impedance of the pipeline steel and the parallel conductance to ground through the pipeline coating. Large PSP variations occur where there is a disruption in the flow of telluric currents along the pipeline, such as happens at the end of the pipeline, at flanges, at bends, and changes in pipeline characteristics. A series of plots are presented showing the dependence of PSP variations on coating conductance, changes in series impedance and bends in the pipeline. Also examined are how the PSP variations are modified when overlapping effects occur. Finally, the paper considers the effect of various mitigation strategies and presents model results of the reduction in PSP variations that can be achieved.