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This paper presents the analysis of grounding systems including freely oriented conductors and metallic plates of arbitrary shapes in horizontal multilayer soils. The analysis method yields not only the scalar potential but also the electric field and current density in the soil in the low frequency limit. Numerical results are provided for various configurations such as a single plate, a plate with rods, parallel plates, a box, or cylinders formed by multiple plates and are verified against available analytical methods. [ABSTRACT FROM AUTHOR]

Service lifetime estimation for earth grounding grids as a problem or a task faced by the industry is presented. A mathematical model based on Freschi's semianalytical model to determine the performance of the earth grounding grid at a certain year after being buried is proposed. The mathematical model can also explain the performance degradation of the earth grounding grid in principle and mathematically. According to the model, a scheme to estimate the service life of the earth grounding grid is proposed. A case study is given to illustrate how the scheme works. If the estimated service life of an earth grounding grid is not satisfactory, some measures, such as cathodic protection, should be considered to extend the service lifetime of the earth grounding grid. [ABSTRACT FROM AUTHOR]

One of the main purposes of grounding systems is to safely inject fault currents into the soil; such currents flow through any buried conductive objects (e.g., other earth electrodes) eventually present along their path to the source. As a result, even though grounding systems may be metallically isolated, they become coupled due to the flow of the earth-current and interferences occur. Due to this unwanted coupling, dangerous potentials may arise over the “passive” electrode, which may expose persons to the risk of electric shocks. This paper proposes a semianalytical approach to evaluate mutual interactions among grounding systems at low frequency, and establishes criteria to evaluate their actual independence. A significant case study of interactions between the substation grid and the safety ground bed in a mining installation is quantitatively discussed. [ABSTRACT FROM AUTHOR]

The analytical study of grounding systems is only possible for basic electrodes, i.e., hemispherical and spherical electrodes, rods, and horizontal wires. However, it is normal practice to employ more complex earthing systems, such as grounding grids integrated with rods, in order to obtain lower resistances to ground and improve the electrical safety of substations. This paper introduces a semianalytical (or seminumerical) method, consisting of an analytical approach integrated with a numerical solution, to study grounding grids of complex geometry and their effects on non stratified soils. The algorithm that was created and realized with MATLAB allows the determination of all the quantities of interest for the design and the analysis of such grounding systems, i.e., ground resistance, ground potentials, and distribution of the ground-fault current along the grid's components (i.e., horizontal wires and rods). The model is based on the assumption that conductors forming grids have very small radii if compared with their lengths and that the wires can be considered equipotential cylindrical elements. A verification of the proposed algorithm through a finite-element method has been also carried out to confirm the validity of the results. Exemplary calculations of the ground resistance of grids are included in this paper. [ABSTRACT FROM AUTHOR]