A calculation model for cathodic protection of underground extensive structures using impressed current cable anodes

Proper design of cathodic protection by use of impressed current cable anodes requires the knowledge of current and potential distribution along the anode and the structure to be protected. The conductive coupling between these earth-return circuits results in different current and potential distributions along both structures when comparing with the case of separate anode. In the paper calculation models - accurate and simplified - are presented. In the accurate model an interchange of currents flowing along both structures is taken into account, whereas in the simplified method the structures are treated as separate earth return circuits. The formulas are derived for calculation of such parameters as longitudinal current, protective current density, potential to the remote earth and potential to the adjacent earth. Calculations have been carried out in which the influence of the distance between the two structures on the values and distribution of currents and potentials along the anode and the protected structure has been examined. The relations presented may be useful at design stage of impressed current cathodic protection systems containing cable anodes.