Modelling Grounding Systems Using the Finite Element Method: The Influence of the Computational Domain Size on the Accuracy of the Numerical Calculation

Simulating the static and dynamic behaviour of grounding systems using numerical methods is a well-established procedure. In order to achieve greater model accuracy, a special attention is usually paid to the construction of more complex models. However, in the modelling process, there are certain factors that have a great influence on the model accuracy regardless of its complexity. They can drastically reduce the accuracy of high-quality complex models. The article elaborates on the ratio influence of the soil dimensions and the dimensions of the buried part of the grounding system, i.e. the influence of the edge distance of the hemispherical soil model from the centre of the grounding system (i.e. computational domain size) on the accuracy of the numerical calculation using the finite element method. In this paper, the physical cause of the influence of the computational domain size on the accuracy of the calculation is explained in detail. The paper gives a mathematical model that accurately describes the influence of the edge distance of the hemispherical soil model from the grounding conductors on the accuracy of the numerical calculation. Based on the presented theory, derived expressions and simulation results, guidelines in the implementation of numerical methods in modelling grounding systems are given. Also, the applicability of these guidelines in other applications such as modelling, analysis and interpretation of resistance data using FEM was considered.