A general formulation based on the boundary element method for the analysis of grounded installations in layered soils

The design of safe grounding systems requires computing the potential level. distribution on the earth surface for reasons of human security, as well as the equivalent resistance of the earthing installation for reasons of equipment protection (Sverak et al.[1], ANSI/IEEE[2]). In the last three decades several methods for grounding analysis have been proposed, most of them based on practice and intuitive ideas. Although these techniques represented an important improvement in this area, some problems such as large computational requirements, unrealistic results when segmentation of conductors is increased, and uncertainty in the margin of error, were reported (Sverak et al.[1], ANSI/IEEE[2], Garret & Pruitt[3]). Navarrina et al.[4] and Colominas et al.[5] have developed in the last years a general boundary element formulation for grounding analysis in uniform soils, in which these intuitive methods can be indentified as particular cases. Furthermore, starting from this BE numerical approach, more efficient and accurate formulations have been developed and succesfully applied (with a very reasonable computational cost) to the analysis of large grounding systems in electrical substations. In this paper we present a new Boundary Element formulation for substation grounding systems embedded in layered soils. The feasibility of this BEM approach for two-layer soil models is demonstrated by solving a real application problem.