Optimal Design of the Vertical Earthing with Electrodes Arranged in Line

Abstract

The design methods of earthing from standards recommend the choice of electrode lengths and propose that the distances between electrodes to be 1-3 times larger than their length. The number of electrodes is determined from the condition of achieving the design earth resistance, while the design ends with the choice of one of the variants. This paper presents the methodology for calculating the earthing system with cylindrical, vertical electrodes arranged in a line. The main variables are the length and the number of earth electrodes, as well as the distance between adjacent ones. Firstly, a set of technologically advantageous values for the earth electrode length is established (e.g., 10 values). For each value of the electrode length and different numbers of electrodes (e.g., 11 values), the distance between adjacent electrodes is determined (e.g., for 110 cases), which leads to the design value resistance. Finally, optimal solutions are identified based on the five optimal applied criteria. The proposed optimal criteria for earthing design are the footprint area, the total earthing volume, the total dispersion surface, the total metal mass, and the investment costs. Comparing the optimal solutions with other technically possible solutions clearly highlights substantial savings concerning space, material, and cost.

Influence of Lightning Current Parameters and Earthing System Designs on Tower Footing Impedance of 500 kV Lines

“…For an SR exceeding 100 Ωm, an additional earth electrode should be added i.e., a rectangular or square horizontal electrode. However, if the soil resistivity is over 4000 Ωm, the use of a horizontal electrode along the tower and connecting an earth electrode to each tower was found to be more effective and was recommended [11,[20][21][22].…”

“…Due to that, the resistivity of the ionized soil drops to a low value and the TFR would be reduced automatically [29]. A review of prior studies shows that the focus has been on earthing behaviour in uniform soil, the soil top layer depth, algorithms and the reflection factors [22,[30][31][32][33]. Several studies have been based on various assumptions and physical techniques, resulting in the development of numerous equations over the last few years.…”

“…Therefore, this paper aims to evaluate the tower footing resistance before and after improving the earthing arrangement. An investigation into the effect of low and high frequency behaviour, based on the specification of the tower footing resistance (TFR) and measurements of soil resistivity (SR) carried out at selected 500 kV TL towers in Peninsular A review of prior studies shows that the focus has been on earthing behaviour in uniform soil, the soil top layer depth, algorithms and the reflection factors [22,[30][31][32][33]. Several studies have been based on various assumptions and physical techniques, resulting in the development of numerous equations over the last few years.…”

The Impact of Substation Grounding Grid Design Parameters in Non-Homogenous Soil to the Grid Safety Threshold Parameters

“…A detailed review of the grounding system behaviors in homogeneous soil conditions has been published in [24]. Although there is extensive research on grounding behavior in uniform [4], [5], [25] and two-layer soil; top layer depth of two-layer soil [14]; the number of grounding meshes [26]; length of ground rods in two-layer soil [27]; algorithms [3], [6], [28] and reflection factors [29], [30] there is still no complete analysis currently available which comprises the impact of grounding grid dimensions, the number of ground rods and the impact of grid depth as the grid design varies in twolayer soil on grounding grid behaviors and safety. Most of the investigations were based on many assumptions and different physical approaches, which resulted in many equations developed over the last few decades.…”

“…P.Navinesshani: The Impact of Substation Grounding Grid Design Parameters in Non-Homogenous Soil to the Grid Safety Threshold Parameters (February 2021)4 VOLUME XX, 2021…”