Performance Of Grounding System Research Articles

A Novel Method for Line Selection for Cross-Line Two-Point Successive Grounding Faults Utilizing Transient and Steady-State Information

In order to improve the performance of an arc suppression coil grounding system in handling cross-line two-point successive grounding faults (CTSGs), the applicability of the transient quantity method and the steady-state quantity method for assessing CTSGs is analyzed. Then, a novel method for line selection for CTSGs was proposed, which comprehensively utilizes transient and steady-state information. Specifically, this method adopts a continuous line selection process, with priority given to the transient quantity method, and a supplementary line selection process, with priority given to the steady-state quantity method. After accurately selecting some faulty lines, such lines are tripped, and then, the process proceeds with continuous line selection again. When the number of cycles exceeds the set value, and the fault line cannot be completely cut off, they are tripped one by one according to the degree to which they are approaching the steady-state method criterion, from large to small. Furthermore, in response to the dramatic increase in computing volume that is caused by the continuous application of the transient method in on-site applications and the impact of current transformer accuracy on the steady-state method, this paper proposes corresponding solutions. PSCAD simulation, full-scale tests, and field recording data tests verify that this paper’s method can accurately detect a CTSG.

Evaluation of the optimum safety performance of the nuclear reactor compact grounding system under lightning strikes and ground fault

Abstract The electrical system of a nuclear reactor facility (NRF) must incorporate a grounding grid in order to ensure it functions safely and reliably. Any disturbance in the electrical system affects the nuclear process, so it is, therefore, crucial to estimate the safety performance of the research nuclear reactor facility grounding system. The paper discusses CYMGrd 6.3, which is based on IEEE Standard 80-2013, and the optimization approaches for finding the best grounding grid design for a nuclear reactor facility connected substation of 500/11 kV in the case of a ground fault and lightning strikes. The result shows that the surface, step and touch potentials along the diagonal coordinates of the proposed grounding grid are below the safety limits in case of a ground fault but also results indicate that 100 kA lightning stroke poses a considerable threat to reactor equipment and personnel safety because the measured grid surface potential exceeds the safe ground potential rise of 3.2 kV standard at the striking point in conjunction with the proposed ground grid, so it must be modified. In this paper, three different optimization algorithms are investigated in order to determine the optimal design of the grounding grid with respect to mesh size: gradient method (GM), the genetic algorithm (GA), and simulated annealing (SA). These methods are used to achieve the purpose of obtaining an effective ground grid design. Comparing these techniques of GM and SA is good for quickly locating local minima, but they may fail to identify global solutions. In contrast, a genetic algorithm is often excellent at achieving a global minimum. Also, the utilization of GA, SA, and GM achieve the reduction of the surface potential of a proposed grounding grid by 16 %, 10 %, and 6 % respectively.

Analysis of grounding system transient with consideration of soil ionization and mutual coupling effect

The grounding system of an electrical substation provides safety to both operator and equipment. The lightning current waveform has a major influence on the dynamic performance of ground electrodes. If lightning current is large enough, soil will be ionized, which will have a great effect on the transient performance of the grounding system. Many numerical models have been developed to evaluate the transient performance of grounding system, still it is a challenging task to analyze the impulse behavior of grounding system efficiently. In this paper, the transient behavior of grounding systems with consideration of nonlinear and dynamic effects of soil ionization is presented. Grounding systems such as vertical rod, horizontal conductor and grounding grid buried in the homogeneous soil are considered as case study. Proposed model is the combination of circuit theory approach and method of moment with consideration of frequency-dependent impedance and mutual coupling effect between the conductor segments. Self and mutual component of inductance and resistance are considered in the analysis. Initially, transient performance of grounding system is analyzed for single vertical rod, horizontal and square grounding electrodes, further it is extended for vertical rod (more than one), horizontal conductor and grounding grids with different configurations. The analysis of grounding system with the consideration of mutual coupling effect is compared with devoid of mutual coupling, and differences between them are evaluated. For validating the developed method, simulated results are compared with the results reported in the literature, and good agreements are found. Analysis shows that the grounding impulse impedance decreased with increasing the magnitude of injected current. Developed method will help to improve the modeling of simple as well as complex grounding system buried in homogeneous soil.

Agrivoltaic approach in improving soil resistivity in large scale solar farms for energy sustainability

Recently, approaches have been established to improve the grounding system performance, especially with the increasing numbers of large-scale solar (LSS) PV farms. Soil resistivity is one of the contributing factors to the inefficiency of power generation as it induces high impedance on electricity flow from the source to highly sensitive PV equipment and devices such as inverters. Some critical issues on nutrient leaching derived from ammonium sulphate fertilizer direct to ground soil are the focal point of this work with the fact that soil resistivity value is inversely proportional to increasing soil salt content. Therefore, a low grounding system could be obtained with a high Electrical Conductivity (EC) and high soil moisture content. In this work, a conceptual setup for an agrivoltaic condition with 500 units of herbal crops has been cultivated directly underneath 1 PV string in Puchong Solar Farm, Selangor, Malaysia. The amount of salt or nutrient under this condition was measured leaching approximately 40 mL per polybag as means of ground treatment to improve soil resistivity value, thus indirectly reducing the risk of electrical damage. The agrivoltaic approach has shown that it can improve the performance of a grounding system in an LSS PV farm with a significant reduction of 4.45 Ω earth resistance on average.

Performance of Backfill Material for Grounding System under High Voltage Condition

Grounding (or earthing) play the main role to in order to protect electrical equipment, building and life from lightning, switching and earth fault occurrences. A good grounding system must be able to dissipated this unwanted charge in very fast time and this can be achieved by reducing the grounding resistance. Introduction to backfill material to be filled into grounding pit is widely implemented in order to lowering the resistance of grounding system. This paper investigates the performance of marconite, cement and sand as part of backfill materials for ufer type grounding system under alternating high voltage and impulse voltage condition. The purpose of high impulse voltage experiments is to determine the performance of above said materials under transient condition while the alternating high voltage experiment to observed the behaviour backfill material under leakage or fault current occurrence. The findings reveal that performance of grounding system may significantly change from the expected result at design stages.

A fast method to compute the grounding resistance of a coated electrode using the coated electrode equivalent radius

The effect of an oxide layer or any conductive material layer surrounding the electrode surface on the performance of grounding system is studied in this paper. The boundary elements method applied to the electrode surface together with the Equivalent Surface Charge Distribution model to assess the contribution of the material-soil interface are used to compute the grounding resistance of an electrode buried in a semi-infinite soil and energized by a low frequency current. Due to the high computation time required to apply the numerical method to find the solution of the problem, the Coated Electrode Equivalent Radius is introduced from the study of the grounding resistance as a tool to simulate the effect of the material layer on the electrode. This equivalent radius is a function of the thickness of the material layer and can be used in common methods for calculating parameters of a grounding system such as grounding resistance and step and touch potentials. The proposed expression for the equivalent radius is tested in several synthetic examples and also in a real case. Some of the tests carried out are also compared with the results of using commercial software.

Performance of different grounding systems of 500 kV XLPE long submarine cables based on improved multiconductor analysis method

The grounding system is a decisive factor in the safety and reliability of submarine cables used for marine transmission systems. In this paper, the accurate matrices of distributed impedance of the submarine cable system are established considering the effect of the multilayer soil laying condition. The improved multiconductor analysis method, which has good calculation efficiency and accuracy, is proposed to analyse the cable grounding system under the steady-state power-frequency operating conditions. The performance of different grounding methods of the Zhoushan 500 kV XLPE submarine cable project in Zhejiang Province of China is investigated. The results show that the grounding methods of solid-bonding with intermediate grounding points and solid-bonding with semiconducting sheath are more promising than the conventional solid-bonding grounding method for the long submarine cable system due to the reduction in the induced voltage of metallic sheath as well as lower power loss. A guideline for the grounding system design of the long submarine cable lines is proposed in this paper.

Effect of Non-Homogeneous Soil Characteristics on Substation Grounding-Grid Performances: A Review

Designing an effective grounding system for AC substations needs predetermination of ground resistance and ground potential distribution caused by fault current’s presence in the ground. Therefore, it is necessary to have a suitable grounding grid structure in the soil properties in which the grid is buried. Though the soil composition where the grounding grid is located is typically non-homogeneous, the soil is often presumed to be homogeneous due to the complexities of grounding system analysis in non-homogeneous soil. This assumption will lead to inaccuracies in the computation of ground resistance and ground potentials. Although extensive research has been done on non-homogeneous soil structure, comprehensive literature on grounding system performance in non-homogeneous soil is yet to be reviewed. Thus, this paper reviews the effect of non-homogeneous soil on the grounding system, with different soil characteristics in horizontal and vertical two-layer soil structure and the horizontal three-layer soil structure. In addition, the effect of design parameters on the grounding performance in non-homogeneous soil conditions for non-transient fault conditions is also studied. The significance of this study is that it provides a comprehensive review of grounding performance as grounding design changes and their effects as soil layers and their corresponding features change. This knowledge will be useful in developing safe grounding designs in non-homogeneous soil.

Effects of various relative humidity conditions on copper corrosion behavior in bentonite

Bentonite is low resistance water retaining conductive clayey material often used as grounding enhancement material, particularly in a troubled environment. Due to its unique property, bentonite retains water and dissipate unwanted electrical current to ground. However, bentonite's water retention capacity would inevitably induce corrosion to the grounding electrode and may jeopardize the grounding system's performance in the long run. This study presents bentonite properties on copper electrodes' corrosion behavior. In this study, copper corrosion behavior buried in Andrassy bentonite specimens was investigated under varying relative humidity conditions using the vapor equilibrium technique. The corrosion rate was calculated at equilibrium, and FESEM later characterized the corroded surfaces. The copper corrosion rate in Andrassy bentonite was found to be between 2.2 and 2.8 × 10-3 mm/year. Test results showed that more water might not necessarily induce and expedite copper corrosion. However, it was noted that copper corrosion was somewhat limited under extremely dry conditions and very wet conditions. On the other hand, RH = 75% was the optimum copper corrosion condition to occur. It is believed that the corrosion of copper specimen may be influenced by other complex mechanism presence of such as chemicals species and microbes contained within the bentonite and surrounding environment.

Effects of Soil Profile on the Transient Performance of Substation Grounding System

<table width="593" border="1" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top" width="387"><p>Lightning transient characteristic of the grounding grid is fundamental for optimum performance of lightning protection of a substation. In order to design an appropriate grounding system for such substation, it is important to study its transient characteristics because the high impulse current is significantly different compared to power frequency current. In this paper, substation grounding grid model was developed using CDEGS software to analyze the grid transient performance in terms of ground potential rise (GPR), touch voltage and step voltage when the grounding system is struck by a lightning impulse current. Several parameters, such as lightning current amplitude, feed point and the number of sub-grids, were altered to study their relationship with the transient performance. The maximum transient GPR, touch voltage, and step voltage increase as the lightning current amplitude increase. The maximum transient GPR and step voltage are the highest at the corner of the grounding grid while the maximum touch voltage is the highest at the centre of the grounding grid. In addition, the maximum transient GPR and step voltage decrease when the number of sub-grid increases. In contrast, the touch voltage slightly increases as the number of sub-grid increases. The maximum transient GPR, and step voltage are the highest at the 2-layer and the lowest at the uniform soil or single-layer soil.</p></td></tr></tbody></table>

Effects of lightning impulse front time on substation grounding system performance

<table width="593" border="1" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top" width="387"><p>The role of the grounding system in the safety of the power system and protection of personnel is obvious during an unexpected short circuit or lightning discharge at the substation. The aim of this work is to analyze the effects of several parameters: lightning impulse front time, soil resistivity and types of grid materials on the grounding system of the Substation. The ground potential rise (GPR), touch voltage and step voltage of a 50 m x 60 m grounding grid buried at a depth of 0.5 m were computed using CDEGS when injected by impulse with different front times. Results show that the shorter the front time of lightning impulse waveform, the higher the value of GPR, touch voltage and step voltage. Meanwhile, when the value of soil resistivity is increased, the value of GPR, touch voltage and step voltage is also increased. Lastly, different types of grid conductor materials give different values of GPR, touch voltage and step voltage. However, it can be said that the differences are too small to be of any significance.</p><p> </p></td></tr></tbody></table>

A new grounding cake to improve the safety performance of grounding systems

The safety of a grounding system plays a vital role in the transmission and distribution network for operational safety in the majorıty of electrical installations. The application of residual current and overcurrent protection relays is among the most preferred methods in grounding systems. A novel grounding cake is proposed in this study to investigate safety performance of grounding system. The methodology is meticulously demonstrated through extensive field experiments on natural and chemical grounding enhancement materials. A performance comparison was carried out between natural and chemical enhancement materials under different humidity levels and voltage stresses. Various adjustable voltages in the range between 0.85 and 3.76 kV were applied to three copper rods vertically planted into different grounding materials. The results from the field experiments were analysed using Discrete Wavelet Transform. The experiments demonstrate that natural grounding enhancement materials give low ground resistivity around the electrodes, serve as a cost-effective solution for high resistive soil, and are in conformity with the IEEE 80 safety standards.

Performance of Galvanized – Steel and Copper Grounding Electrodes Using Bentonite and Coconut Husk Ashes as an Additives Material to Grounding System

Natural enhancement material often uses to improve performance of the soil resistivity in grounding system. Due to the different soil condition, focus for effective grounding go to the soil itself. Soil resistivity, moisture content and surrounding environment contribute to the impedance of the grounding. The usage of material to enhance the grounding can be considering important to maintain the grounding system performance. There are several techniques used to treat the soil using chemical substance known as grounding enhancement material. This technique produces low resistivity to the grounding electrode however the soil become contaminated. This paper will discuss about the performance of coconut husk ashes and bentonite as natural enhancement material and method being used to evaluate the results.

Analysis of Lightning-Related Stress in Transmission Lines Considering Ionization and Frequency-Dependent Properties of the Soil in Grounding Systems

This article analyzes the performance of grounding systems buried in the ionized soil during the lightning discharge. To this aim, at first, a method to simultaneously analyze the transient response of grounding system considering the time-dependent nonlinear behavior arising from soil ionization and frequency dependence of soil electrical parameters related to the frequency content of the lightning surge is presented. The proposed method is performed by a combination of the harmonic balance method and the method of moment, which is aimed at representing an equivalent circuit to model the grounding system during the lightning discharge. The proposed model is validated by comparing the associated results with the published measurement and the numerical data for different grounding systems. Finally, an application of the proposed method is presented and the generated overvoltages across the insulator string caused by lightning strokes, the outage rates of transmission lines, and the lifetime of surge arresters are discussed.

Parametric dependence of lightning impulse behavior of grounding electrodes buried in a dispersive and ionized lossy soil under first- and subsequent-stroke currents

Purpose The purpose of this paper is to investigate the simultaneous effects of ionization and dispersion of soil on the impulse behavior of grounding electrodes under first and subsequent stroke currents. Design/methodology/approach A recently introduced technique called improved multi-conductor transmission line (MTL) is simplified for grounding electrodes buried in both-affected soils. Findings The simulation results show that including the two effects simultaneously in highly resistive soils under high-valued subsequent stroke current is recommended. Otherwise, simultaneous effects can be disregard. Originality/value To the best of the authors’ knowledge, there is no research on sensitivity analyses for the simultaneous inclusion of the two effects on the effective length and the induced voltage on the soil surface. To this end, the simplified MTL is applied to the grounding electrodes. The simulation results show that the computational efficiency in comparison with previous methods is, first, considerably increased. Second, the simultaneous effects result in decreasing the soil surface voltage with respect to situations where either ionization or dispersion is taken into account (single-affected soils). In other words, the performance of grounding systems is improved. Third, the effective length in both-affected soil is has a middle value with respect to the single-affected soil. Such findings practically and financially are of importance.

Analysis of the Behaviour and Effect of Grounding Filler Materials on Grounding System

The grounding system plays an important role in the electrical system part as it gives protection during fault or lightning occur. The main purpose of the grounding system is to protect humans, electrical appliances and buildings from electrical shock due to lightning or another form of electricity that hazardous. Thus, to install an excellent electrical system and complete its circuit, a grounding system performance must be taken into account. But, in certain cases, due to the geological condition, the soil resistivity is not good enough. Therefore, enhancement filler material has been used to reduce grounding resistance. In this project, it is aimed to elaborate on the usage of Coconut Husk, Paddy Husk, and Bentonite as grounding filler materials to reduce the soil resistivity and improves the grounding system. The result showed that Bentonite showed better performance compared to Coconut Husk and Paddy Husk.

Impact of Frequency-Dependent Soil Models on Grounding System Performance for Direct and Indirect Lightning Strikes

The goal of this article is to investigate the effect of frequency-dependent soil models on the performance of grounding electrodes subjected to lightning strikes. Several soil models are examined while accounting for the variation of soil resistivity and permittivity as a function of the lightning current frequency spectrum. The analysis is performed for a homogeneous soil and a two-layer horizontally stratified soil. The impact of the frequency-dependent soil parameters on the ground potential rise (GPR) of simple grounding electrodes subjected to lightning is analyzed and discussed. The analysis is performed in the frequency domain and in the time domain. A wind turbine and its grounding system are also considered in this article. Special attention is given to the case of indirect lightning, rarely mentioned in the literature. The GPR of the grounding electrodes is examined when the frequency dependence of the soil is taken into account and the lightning channel is located at close distances to the electrodes. Indeed, the level of induced electromagnetic fields caused by a nearby lightning channel can still be too high and potentially dangerous. The computations are performed using an efficient Method of Moments (MoM) numerical tool based on surface-wire integral equations for a stratified medium in the frequency range from dc to several MHz. Numerical results demonstrate that the frequency dependency of the soil parameters results in a decrease of the potential rise of the grounding electrodes, with respect to the case where the parameters are assumed constant.

Time domain solution of electromagnetic radiation model of the grounding system excited by pulse current

This paper deals with an advanced electromagnetic radiation approach for analyzing the time-domain performance of grounding systems under pulse excitation currents. The model of the grounding systems presented within this paper is based on the homogeneous Pocklington integro-differential equation for the calculation of the current distribution on the grounding system and Lorentz gauge condition which is used for the grounding system transient voltage calculation. For the solution of the Pocklington integro-differential equation, the indirect boundary element method and marching on-in time method are used. Fur- thermore, the solution technique for the calculation of the grounding system transient voltage is presented. The numerical model for the calculation of the grounding system transients was verified by comparing it with onsite measurement results.

Analysis of the lightning impulse and low-frequency performance of wind farm grounding systems

Previous analysis of the lightning response of wind turbine grounding systems has often considered only one unit. This paper investigates the impulse and low-frequency performance of isolated and interconnected grounding systems of wind turbines, subjected to lightning currents representative of first and subsequent negative downward strokes and return strokes associated with upward negative flashes. The system behavior is studied for different lengths of interconnecting conductor between adjacent grounding systems and for distinct values of soil resistivity considering frequency-dependent soil parameters. It is shown that in the case of lightning currents with shorter front-times, the interconnection improves the impulse response of grounding, reducing the GPR peak, only for soils of higher resistivity, whereas in the case of currents with longer front-times, the interconnecting improves the impulse response in all cases. The relative improvement of the impulse response when the adjacent grounding systems are interconnected becomes more significant with the increase of the soil resistivity. In all cases, interconnecting the grounding systems strongly reduces the low-frequency grounding resistance seen by each individual wind turbine earth termination.

Comprehensive Modeling of Grounding Electrodes Buried in Ionized Soil Based on MoM-HBM Approach

This paper presents a new approach for modelling grounding electrodes buried in two layers soils considering frequency-dependent modeling of soil parameters together with the time-dependent nonlinear behavior arising from soil ionization caused by a lightning current discharge through the grounding system. To this aim, in the absence of soil ionization, a Norton's equivalent circuit is extracted in the frequency domain by means of the method of moment. Then, by adding the nonlinear load representing soil ionization to the Norton's equivalent circuit, the grounding system is changed into a nonlinear Norton's equivalent circuit and treated by using the harmonic balance method. The proposed model is validated by comparing the associated results with published measurement and the numerical data obtained with low- and high-magnitude impulse currents. The results prove that the proposed method is reliable and effective. Finally, an application of the proposed method in predicting the lightning overvoltages across the insulator string is presented and the performance of grounding system for different parameters is discussed.