Mitigation of Interference in Impressed Current Cathodic Protection

Abstract

This paper considers the strategies for the mitigation of the interference of Stray Current (SC) on Impressed Current Cathodic Protection of the American Petroleum Institute specification API 5L grade B pipeline carrying liquefied gas. SC shifts cathodic protection from its designated negative value, and hence expose the pipeline to corrosion. A model for SC was developed and then applied in MATLAB. From the given conditions of operation, an SC of 0.74 mA was obtained, with parametric simulation indicating a rise in SC as anode current output rises. On the other hand, the consequence of the distance of different pipeline from the ground level shows an inverse relationship, which is attributed to the resistance offered by the ground. In order to mitigate the influence of SC interference, two methods have been proposed in this study, the first being anode current reduction or source removal and the second option is increasing distance from the ground bed. To effectively mitigate against the stray current, the pipeline should be sufficiently buried over a distance of 5 m away from the ground bed, while the anode current should be operated as low as 3.5 mA, or better still the interfering source should be removed on the ground that the interfering source was installed after the installation of the protected pipeline.