Soil Heating around the Ground Electrode of a HVDC System by Interaction of Electrical, Thermal, and Electro-Osmotic Phenomena

This article evaluates the influence of several parameters interacting in the electrical, thermal, and electro-osmotics phenomena that rule the transient/dynamic behavior of the soil temperature rising process. The aim is to provide a safe design of ground electrodes concerning the risk of soil collapse ("vitrification") as a consequence of thermal instability. An objective electro-osmosis modeling rather accurate, applicable to generic geometries of ground electrodes, not only for homogeneous but also for nonhomogeneous soils has been developed. Sensitivity analysis correlating design parameters and the grounding behavior for a basic geometry of a toroidal ground electrode is shown herein. The inadequacy of the simplified methodologies available in the technical literature leads to inconclusive results in terms of installation safety, taking into account the omissions of the electro-osmosis phenomenon.