Numerical analysis and safety design of grounding systems in underground compact substations

Abstract

This paper presents a mathematical and numerical formulation to design and analyze grounding systems in underground electrical substations. The developed approach is based on the well known Maxwell’s Equations. The proposed problem is solved by means of the Boundary Element Method (BEM). The utilization of BEM allows to introduce the geometry and electrical characteristics of the enclosure in a uniform soil. Therefore, a more realistic approximation of the soil structure is achieved. This formulation allows to obtain the main parameters of these protection systems (the grid resistance, the Ground Potential Rise, and the step and mesh voltage). It also allows to compute the surface and step voltage distributions. In addition, as a secondary result, the voltage and current density distributions over the enclosure are obtained. Finally, two grounding system analyses of real underground electrical substations are presented to demonstrate the industrial application and the modelization capabilities of the proposed formulation.