Grounding resistance calculation using FEM and reduced scale model

The grounding grid of a substation is one of the most important parts in an electrical system from the point of view of the safety of the people and equipment. Depending on the nature of the phenomena involved in the system is fault or lightning current, the behavior of grounding system is considered under steady state or transient point of view. For safety purpose of grounding grid, the ground resistance is more likely calculated by analytical or numerical method by using potential distribution calculation along soil structure. In comparison with the analytical method, finite element method (FEM) method in calculation of grounding resistance is more flexible in analyzing asymmetrical geometry of the grid, as well as in case of anisotropy of soil resistivity. However, with the increase in size and complexity of substation grid, the FEM method could not be applied due to the increase of divided elements. This paper presents a reduced scale model for grounding resistance calculation using FEM method. The results giving the effect of electrode configuration on potential profile and grounding resistance are also presented.