Abstract
Since 1956, Nickel-KOH polarization cells have been widely employed to safely isolate pipe-type and directly buried power cables. The steel pipes and metallic sheaths are metallically separated from contact to the electrical grounding network of interconnected foreign structures. Cathodic protection of these pipelines and sheaths is maintained at fully polarizing potentials. Full electrical continuity is provided through polarization cells, which are inserted in the neutrals between these safely isolated structures and the grounding grid.
Since 1971, many other types of structures have been similarly protected by inserting polarization cells in their neutrals, or between the structures and the grounding network. Uniform cathodic polarization results when all structures are electrically continuous with the grounding grid. In good designs, the vital electrical grounding grid and its interconnected foreign structures are safely preserved from interference, because they no longer carry stray currents, originating from cathodic protection systems. Protective d.c. is confined to only those selected structures which are safely isolated, and therefore remain immune to the adverse effects of both a.c. and d.c. Often, by enhancing cathodic protection effectiveness, the protective current requirements have been reduced by up to 75% or more.
