Evaluation of ground resistance of a grounding grid of any shape

This paper presents the safety assessment of a grounding system at an indoor-type 161/23.9-kV substation based on voltage dependent body resistance. For a grounding system to be safe, the maximum actual touch and step voltages should not exceed postulated safety criteria. Thus, safety assessment of a grounding system is referred to a procedure by which the actual maximum touch and step voltages are computed and compared to the maximum allowable (safe) touch and step voltages. The safety criteria in terms of allowable body current have been defined by two widely accepted standards, i.e., the IEEE Std. 80 and the IEC 60479-1. Then, the allowable body current is translated into the allowable touch and step voltages. However, the two standards differ in their definitions of body resistance. The IEC 6047-1 provides data for the body resistance as a function of body voltage and data for the body resistance as a function of path; while the IEEE Std. 80 uses a constant value of 1000 ohms for the body resistance. Thus, a comparison of allowable touch and step voltages computed by these two standards is included in this study. 7Kung University in Taiwan. His research interests are power system grounding analysis, power system transient modeling, and applications of wavelet theory in power systems. received the M.E. and E.E. A. P. S. Meliopoulos

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“…This resistance is to be computed with the equation of Table I or with computer based methods, for example references [8][9].…”

Section: The Proposed Approachmentioning

confidence: 99%

Safety Assessment of AC Grounding Systems Based on Voltage-Dependent Body Resistance

Lee

Meliopoulos

2015

IEEE Trans. on Ind. Applicat.

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“…For example, the basic steel mesh frame can be fully utilized as a natural grounding electrode in wet areas with soil resistivity 100 ρ ≤ and areas with operational experience; the grounding device should surround the tower foundation laid as a closed loop in residential areas, paddy fields and other horizontal grounding electrode where restrictions are imposed; the grounding device uses a radial grounding electrode or a continuously elongated grounding electrode in a wider area; Several copper rods, steel rods and angle steel are penetrate into the ground vertically as the grounding electrode in the steeper western China. The above conventional installation methods have disadvantages [2][3]. For example, the natural grounding electrode has the problem that the current discharge is difficult to meet the expected requirements; the closed loop grounding device has a deep buried depth and the applicable range is limited; the long length of horizontal grounding electrode increases the construction difficulty and cost.…”

Section: Introductionmentioning

confidence: 99%

A new grounding model for complex soil environments

et al. 2019

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The purpose of arranging the grounding electrode is to discharge large currents, such as fault current and ensure the transmission line operate safely. In the grounding system of Chinese transmission network, the common grounding electrodes are horizontal installation and vertical installation. But two installation methods usually have the disadvantages, which are long distance installation and large depth burying, and they are restricted susceptible to uncertain factors such as pipelines, roads and geology, which leads the grounding resistance increasing and affect the normal operation of transmission lines. In order to solve the problem, this paper presents a new grounding model for complex soil environments and analysis from grounding resistance, surface potential and current distribution. The results show that the helix grounding electrode has good resistance reduction performance in complex soil environment, which effectively improves the surface potential distribution and the distribution of the spill current.

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“…Ref. [3] presented an analysis on evaluating grounding grids of different shapes in substations. Different shapes of grounding grids have also been considered in [4] in calculating ground resistance using the finite-element method (FEM).…”

Section: Introductionmentioning

confidence: 99%

“…A scheme was proposed in [8] for calculating the ground resistance using FEM to the resolution of solid models in 3D view. As discussed in many literatures including [3,4,7], although FEMs are the most accurate methods for computing grounding grid resistance, these methods are quiet complicated and time consuming for grounding system design purpose. In [9], it is shown that the low or high resistivity soil layer formed in raining or freezing season affects the safety of grounding system, and leads to the changes of grounding resistance of the grounding system, step and touch voltages on the ground surface.…”

Section: Introductionmentioning

confidence: 99%

Soil resistivity and ground resistance for dry and wet soil

Salam

Rahman

Ang

et al. 2015

J. Mod. Power Syst. Clean Energy

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In this paper, soil resistivity and ground resistance at two different sites near an electrical substation are measured using a grounding system grid with and without rods. With the Wenner four-pole equal-method, the soil resistivity is measured at both selected sites, one of which contains wet soil while the other contains dry soil. Cymgrd simulation software is then used to determine the acceptability of these measured resistivity values by finding out the root mean square error between the measured and calculated values for both wet and dry soil sites. These values for wet and dry soil sties were found to be only 0 % and 4.92 %, respectively, and deemed acceptable. The measured soil resistivity values were then used to evaluate the ground resistance values of a grounding grid 'with rod' for the wet soil site and 'without rods' for the dry soil site, and then compared with the simulated ground resistance values. These comparisons were also found to be in good agreement. In addition, ground potential rise, maximum permissible step and touch potentials have also been estimated using the simulation software.

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Evaluation of ground resistance of a grounding grid of any shape

Cited by 37 publications

References 9 publications

Safety Assessment of AC Grounding Systems Based on Voltage-Dependent Body Resistance

Safety Assessment of AC Grounding Systems Based on Voltage-Dependent Body Resistance

A new grounding model for complex soil environments

Soil resistivity and ground resistance for dry and wet soil

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