MODELING OF UNDERGROUND CATHODIC PROTECTION STRAY CURRENTS

OKAPPI, a numerical model for calculating cathodic protection (CP) pro blems involving underground pipelines, was extended to situations invo lving stray currents.(1) Aboveground structures such as rail bars, pow er stations, electric train or tram vehicles, and overhead lifelines w ere integrated in the existing model in a straightforward and transpar ent way. As a result, it was shown that the model can be used to deal with most of the CP problems encountered with underground pipes. Situa tions where the sources of stray current, such as other CP installatio ns or earthing systems located in the soil, were modeled and compared with theory. Cases involving the four standard kinds of CP interferenc e (anodic, cathodic, combined, and induced) were calculated and discus sed. A few complex situations involving overhead systems such as trams or railways were investigated. The theoretically expected phenomena w ere confirmed by the calculations.