Evaluation of the voltage distribution around toroidal HVDC ground electrodes in n-layer soils

A method for evaluating the electrical voltage and the current density in the immediate vicinity of a toroidal grounding installation of DC substations is presented. In order to guarantee that voltage rises generated during operation are within safe limits and considering the need to reduce the dimensions and costs of grounding installations, it is necessary in certain cases to improve the soil model in the area affected by the electrode. Electrostatic theory is used to generate a voltage solution for the Laplacian equation for n-layer soil models, and computed voltage profiles are shown in the vicinity of an actual electrode. Theoretical results for a two-layer soil model are also presented, along with measurements carried out on a reduced-scale electrode