Comparative assessment of the effect of earthing grid configurations on the earthing system using IEEE and Finite Element Methods

Abstract

In this paper, comparative assessments of four earthing grid system configurations (the triangular shape, the rectangular shape, the T-shape and the L-shape) are performed with the aim of determining the best earthing grid configuration in terms of earthing grid resistance, Ground Potential Rise (GPR), touch voltage and step voltage for a typical food and beverages industry in Nigeria. The IEEE earthing technique and the Finite Element Method (FEM) are employed to simulate the earthing grid system configurations using commercially available software (Electrical Transient Analyser Program, ETAP 12.0). The results revealed that L-shape is the most preferred earthing configuration in terms of grid resistance, GPR and step voltage with the IEEE values of 0.292Ω, 1610.9 V and 436.5 V, respectively and FEM values of 0.195Ω, 1077.1 V and 186.6 V, respectively. Meanwhile, the rectangular shape gives the best result for designed touch voltage with the value of 284.5 V for the IEEE method and 286 V for the FEM method followed by the L-shape with the values of 340.8 V for the IEEE technique and 294.8 V for the FEM. Both the IEEE method and the FEM return the same trend of result for all grids. However, IEEE method is much better in terms of computational speed. Keywords: Earthing grid system, Earthing Configurations Electrical Transient Analyser Program (ETAP), Finite Element Method (FEM), IEEE earthing technique