Soil heating around the ground electrode of an HVDC system by interaction of electrical, thermal, and electroosmotic phenomena

The present article evaluates the influence of several parameters interacting in the electrical, thermal, and electroosmotics 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 electroosmosis 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 unconclusive results, in terms of installation safety, taking into account the omissions of the electroosmosis phenomenon.