Optimisation of Earthing System Design through Touch Voltage Minimisation Using Ansys Maxwell

Earthing system design is usually assessed based on the permissible touch voltage curve of EN 50522. The touch voltage is driven by the spatial placement of the earthing system electrodes, i.e. rods, strips, rings etc. Basically, if one wants to optimize the design, appropriate spatial placement of these electrodes has to be found. As this optimization could be quite challenging, it is usually based on the designing engineer experience and the final solution might not always be the optimal one. Thus, in this paper a software based (Sequential Non-Linear Programming) optimization technique is used to search for the 'optimum' solution of earthing system design by Ansys Maxwell. A simple double ring earthing system model was placed in horizontally stratified soil model with two layers and through the optimisation the burial depths of both rings were found. As the optimisation objective function the actual touch voltage was used. It was found that in most cases the Ansys Maxwell optimiser found the optimal design, however in a few cases more variations of earthing system were found with equal value of objective function meaning that possible local and global minimums can be expected.