Grounding Impedance Characteristics for Two-Layer Soil of Vertical Rod Configuration with Variation of Length and Diameter

Abstract

Abstracts: Grounding impedance is an important component of electrical power systems especially for protection for human safety and the continuity of the operation of power systems. At low frequency current injection the characteristics of grounding impedance is very resistive, however at high frequency it may be capacitive or inductive depending on the frequency. In order to build a grounding system used for lightning protection, it needs a careful and accurate design. It will receive high current and high frequency around hundred kilos up to mega hertz, otherwise it is simple grounding for low frequency. This paper reports the modification of a grounding system with vertical layers configuration. This is the novel issue because the other researchers use horizontal layers configuration. In this experiment, the grounding rod is injected by using low to high frequency AC source The modification is made by filling the soil into a grounding rod (cylinder rod) and therefore it created two soil layers of grounding system, and by using three size variations of cylindrical layers of length (L) of 40, 60, and 100 cm; and three size variations of diameter (D) of 20, 30, and 40 cm. These variations will allow us to understand the characteristic of the grounding impedance at low and high frequency, where usually the composition of inner layer soil have lower resistance than the outer soil. The composition of the outer soil consist of 16.85 % clay, 66.18 % silt, 15.48 % sand, and 1.49 % gravel whereas the composition for the inner/filling soil consist of 34.98% clay, 49.55% silt, 15.35% sand, and 0.16% gravel. The value of soil permittivity and resistivity affect the value of grounding impedance at low and high frequency. In general, the results indicated that the grounding impedance at high frequency was higher than at low frequency, but the fluctuation of grounding impedance depended on the condition of inner soil, length and diameter of cylindrical rod. In this research, the grounding impedance was plotted as the function of the frequency and until now the value of this fluctuation cannot be determined accurately.

Perancangan Sistem Pentanahan Pada Laboratorium Terpadu Fakultas Teknik Universitas Bengkulu Dengan Metode Two-Layer Soil Vertical Rod Configuration

“…Penentuan konfigurasi pentanahan berdasarkan kebutuhan proteksi dan wilayah pada sistem pentanahan, pada wilayah yang luas dapat dilakukan sistem pentanahan horizontal (grid/mesh) dan untuk wilayah proteksi yang relatif sempit sistem pentanahan dirancang secara vertikal (rod) [7]. Perancangan sistem pentanahan dalam instalasi listrik dilakukan dengan pengujian tanah untuk mengetahui kondisi tanah, pengujian dilakukan harus disesuaikan dengan standart yang berlaku.…”

Assessment of the Grid Safety Values for Substation Grounding Grid Design Parameters in Vertical Two-Layer Soil Structure

“…Most substation grounding system safety evaluations and design procedures employ a homogenous soil environment as an input to calculate safety values (grid impedance, step, and touch voltages). However, despite significant studies into grounding behavior in homogenous soil environments (Mokhtari et al, 2016a;Nikolovski et al, 2016;Pavel et al, 2020) and horizontal two-layer soil with varying soil properties such as the upper layer height (Zaini & Ghoneim, 2012) and the soil reflection factors (K) (Gouda et al, 2019;Tong et al, 2019) and varying grid design parameters such as the analysis of single horizontal grounding conductor (de Araujo et al, 2019;Arnautovski-Toseva et al, 2007), the mesh count of a grounding system (Unde & Kushare, 2012), vertical rod length (Anggoro et al, 2018), there is presently no comprehensive study available that assess the grounding behavior in vertical two-layer soil under the impact of design parameters. Furthermore, no simultaneous comparisons or discussions between horizontal and vertical two-layer soil structures are available.…”

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.…”