Assessment model for monitoring AC induced interference corrosion of buried pipelines from HVTLs

Alternating current (AC) induced interference corrosion has been a major threat to pipeline sharing right of ways with AC high voltage transmission lines (HVTL). Defects occur on these pipelines due to the dielectric breakdown of the pipe coating as a result of appreciable voltage being induced on the pipe from the nearby transmission lines. These defects cannot be easily assessed by inspection of the pipe´s surface as the pipeline of interest is buried below the soil surface. The value of AC current density through these coating defects has to be monitored not to exceed the threshold value that can cause corrosion damage to the pipe. In view of this, we present an assessment model given input data from field measurement, for monitoring of AC induced corrosion of an underground pipeline co-located with four single circuits HVTL of horizontal geometry. The results obtained showed that the pipeline is exposed to corrosion damage for soil with low electrical resistivity. AC current densities increase as the magnitude of the induced voltage on the pipe increases. The results also showed that the relative risk of corrosion damage also high at that area. We also provide a user friendly MATLAB-based graphical user interface to facilitate easy usage of the developed assessment model.