Design Cathodic Protection Ground-Bed Arrangement with Finite Element Analysis Method

A more flexible grounding resistance calculation method, based on finite element analysis (FEA) method, is suggested, which is especially suitable for optimization cathodic protection (CP) ground-bed arrangement. As compared with traditional grounding resistance evaluation method, which is only suitable for the case of each anode rod in a straight line, the FEA method can calculate grounding resistance of ground-bed at any arrangement. Moreover, a realistic soil resistance rate, usually varying with depth, can be included in calculation model. The detailed steps for this method can be summarized as follow: building a 3D geometric model according to general design, meshing the geometric model, setting reasonable boundary conditions, solving and post-solving the grounding resistance with ohmic law. To further explain this procedure, a realistic CP ground-bed displacing project is presented, which includes displacing the original CP ground-bed firstly and re-designing a new ground-bed within a limited area (5m×30m). A new CP ground-bed design, compared with traditional design, 2×7, 14 anode rods dispersed in two parallel groups, are calculated firstly. The results show that this design can not meet the grounding resistance requirement. Another 4 designs, with anode rods arranged as 2×6, 2×8, 2×9, 3×6 are calculated respectively. Finally, the design 2×8 is recommended from the view of economy and practicability.