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Abstract This paper aims to propose a method for the design of the substation grounding grid in China Fusion Engineering Test Reactor (CFETR). In order to evaluate the safety of the grounding grid, Electrical Transient Analysis Program (ETAP) was used to simulate the fault current, contact voltage, and step voltage, and the results are compared with theoretical calculations to verify the correctness of the design. This will help reduce faults caused by the defects of grounding grid This method is special in that the designed grounding grid not only meets the requirements of relevant standards, but also reduces the number of conductors. During the design process, factors such as voltage level, fault location, and soil resistivity were fully considered to adapt to different occasions. This method can also guide the design and renovation of grounding grids for other buildings in CFETR.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

One essential requirement for grounding grid state detection is quick and accurate localization of the topology. The combined source detection approach works well for increasing the signal amplitude and detection efficiency inside large grounding grids. However, the presence of bypass branch currents and grounding grid breakpoints causes variations in the location calculated by the peak approach during tiny grounding grid topology detection. The magnetic field superposition method under the excitation mode of multiple sources exacerbates this positioning error. This paper presents a topological feature accumulation imaging method designed for combined sources to address this problem. The proposed approach examines the effect of the bias in the surrounding branch current amplitudes on topological localization by utilizing the concepts of electromagnetic induction. The factors contributing to increased topological localization errors were examined by investigating the relationship between the superposition effect of the surface magnetic induction strength and localization error under different combined excitations, particularly in the context of breakpoints in the grounding grid topology. The proposed method uses the top-hat algorithm to extract top-hat features of the amplitude of the surface magnetic induction intensity under every type of excitation. Top-hat eigenvalue accumulation was used to reduce topological localization offsets by mitigating superfluous signals. The advantage of this method over conventional processing approaches is demonstrated by simulations and test field experiments, which show enhanced accuracy in combined source topological localization for small grounding grids.

The corrosion of grounding grid materials in soil is a prominent factor in power and electrical equipment failure. This paper aims to delve into the corrosion characteristics of grounding grid materials and the corresponding methods of safeguarding against this phenomenon. Firstly, the influencing factors of the soil environment on the corrosion of the grounding grid are introduced, including soil physicochemical properties, microorganisms, and stray currents. Then, the corrosion behavior and durability of common grounding grid materials such as copper, carbon steel, and galvanized steel are discussed in detail and compared comprehensively. In addition, commonly used protective measures in China and outside China, including anti-corrosion coatings, electrochemical protection, and other technologies are introduced. Finally, it summarizes the current research progress and potential future directions of this field of study. [ABSTRACT FROM AUTHOR]

Magnetically coupled resonant technology is a novel method for solving the breakpoint locating of power grounding grid. But the method can only detect breakpoints of a single mesh grounding grid at present. In this paper, a magnetically coupled resonant detection method for four-hole grounding grid breakpoint is proposed. Firstly, the equivalent circuit model of the four mesh grounding grid with two types of breakpoints, namely edge branch and intermediate branch, is established. The input impedance and phase angle of the system are obtained by analyzing the equivalent capacitance and equivalent resistance in the model. Secondly, the magnetically coupled resonant physical process of grounding grid faults is solved via HFSS software. The magnetic field intensity and phase frequency characteristic curves of four mesh holes with different branches and positions of breakpoints and different corrosion degrees are studied, and an experimental system is built to verify the feasibility. The results show that under the condition of grounding grid buried depth of 0.5 m and input frequency of 1∼15MHz, and there is an inverse relationship between equivalent capacitance and distortion frequency, the phase angle is positively correlated with the degree of corrosion of grounding grid, and the error of signal distortion frequency can be positioned at 5%. This paper provides some ideas for the application of magnetic coupling grounding grid detection technology.

When the substation grounding grid and part of the underground metal pipe grid are close to each other, the two produce resistive coupling, and the current of the transmission line will flow through the grounding body and through the soil to the buried pipe grid, which may break through the anti-corrosion layer of the pipe grid, and may burn the body of the pipe grid in serious cases; the underground metal pipe grid will also have an impact on the parameters of the grounding grid. To this end, this paper is based on the numerical calculation method of field-path coupling, combined with the actual situation of substation, using CDEGS and ETAP software to simulate and analyze the current dissipation process when a short-circuit fault occurs in the substation after the ground grid is put into operation under multi-layer soil environment, and to study the influence of resistive coupling between the grounding grid and the surrounding metal pipe grid during an industrial frequency grounding short circuit. Optimize the structure of the grounding system so that the contact voltage across and step voltage is lower than the safety limit to protect the personal safety in the station; at the same time, take certain protective measures to slow down the corrosion of the pipe grid. [ABSTRACT FROM AUTHOR]

On the basis of the method of moments, the resistive coupling effect between the newly built grounding network. When the horizontal distance between two grounding networks of a substation changes, this original grounding network of a certain substation is analyzed. And establish corresponding soil models based on actual engineering soil resistivity data. Use the grounding grid analysis function of CDEGS software and Powerstation software simulation software to simulate and calculate some parameters of the new and old grounding grids. The analysis parameters mainly include the grounding resistance, step voltage, and contact voltage of the grounding grid system. And the obtained parameter indicators are compared and analyzed with safety limits to determine the safety performance of the newly built grounding grid system in the substation. And the impact on the grounding performance of the original grounding network of the substation. Provide certain theoretical data support for the actual promotion of substation grounding network engineering. [ABSTRACT FROM AUTHOR]

Assessing the condition of a grounding grid is key to ensuring the safety of a substation and the personnel working in its vicinity. This paper analyzes the static fields of a grounding grid to evaluate its robustness. The proposed method calculates the resistance of a grounding grid by considering the magnetic field generated by the grounding conductor at the earth’s surface and the electric field inside the conductor. By comparing the calculated resistance values of the grid conductors with the designed values, the robustness of the grounding grid is evaluated. The error achieved by this method is 2.46%. Unlike existing methods, such as optimization and the gradient method, the proposed method does not require tedious calculations and is immune to noise induction. This is demonstrated through a comparison with one of the latest research studies. The feasibility and accuracy of the proposed approach in evaluating the robustness of a grounding grid are discussed. Furthermore, the results are supported by the mathematical reasoning and simulation results.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As one of the most widely used forms of energy, the safety and stability of power systems are crucial to modern society. Grounding grids dissipate current and reduce touch and pace voltage during lightning strikes or fault currents, ensuring the safety of personnel and equipment. However, prolonged submersion in soil causes inevitable corrosion, compromising grounding efficacy by increasing resistance and reducing current dissipation. This deterioration can result in unsafe local potential differences. This study uses Laser-Induced Breakdown Spectroscopy (LIBS) to measure corrosion degrees in grounding grids. Spectral data from samples with varying corrosion extent were collected, with outliers removed using the Local Outlier Factor (LOF) algorithm. Principal Component Analysis (PCA) reduced data dimensionality, revealing clustering in spectral data corresponding to corrosion extent. Three machine learning models were compared: Adaptive Boosting - Backpropagation Neural Network (Adaboost-BP), Support Vector Machine (SVM), and Random Forest (RF). The RF model showed the highest accuracy in predicting corrosion degree (R²=0.9845, MSE=0.0296), outperforming Adaboost-BP and SVM, especially for intermediate corrosion extent. These findings validate the effectiveness and reliability of combining LIBS with machine learning for predicting grounding grid corrosion, providing a theoretical foundation for the safe operation of power systems. [ABSTRACT FROM AUTHOR]

The grounding grid transient behavior is an important substation design criterion. This behavior is determined through interaction with impulsive currents typical of lightning. Based on the technical literature, the behavior in question is determined considering fixed current waves, with median parameters (peak values and front and tail times etc.). Therefore, important statistical–probabilistic characteristics of lightning currents, such as correlations and statistical regressions, are not included. From this perspective, this paper includes research into the sensitivity of impulsive impedance and effective area values of substation grounding grids in relation to the waveform of currents typical of the first return strokes. The results (original) illustrate significant sensitivity of the grids transient behavior in relation to those mentioned statistical–probabilistic characteristics, considering a wide range of resistivities in both current injection points considered in this study. • Novel study on lightning current waveforms' impact on grounding grid behavior. • Statistical–probabilistic characteristics influence impulsive impedance and effective area. • Use of Heidler functions to model first return stroke lightning currents. • Significant sensitivity of grounding grids to lightning current waveform parameters. • Implications for substation design and grounding grid performance optimization. [ABSTRACT FROM AUTHOR]

Grounding grid fault diagnosis is essential for the safe operation of a substation. However, the substation vicinity is highly electromagnetic. Therefore, the electromagnetic-based fault diagnosis is vulnerable to electromagnetic interference (EMI). This paper presents the gradient electromagnetic method for the grounding grid fault diagnosis but unlike the previous methods, fault diagnosis here includes the breakpoints and percentage corrosion simultaneously. The diagnosis is based on comparing the calculated resistivity with the designed resistivity of the grid. The resistivity is calculated from the grid’s surface electric and magnetic fields. Furthermore, the existing literature, emphasis on EMI is negligible with the main focus on fault diagnosis only. Therefore, to cope with the EMI, we utilized the Independent Vector Analysis (IVA) to isolate the grounding grid signal from the interfered signal. The validity of IVA is examined by comparing with different known isolation algorithms considering various evaluation criteria. The mathematical reasoning, simulation results and experimental output illustrate that the gradient electromagnetic method along the IVA is feasible for grounding grid fault diagnosis under substation electromagnetic environment (EME).

Lightning strikes in substations may result in extremely uneven ground potential distribution, which will threaten the safety and stability of equipment in substation. However, the main parameters for evaluating the performance of grounding grids are grounding resistance and impulse impedance, and little attention is paid to the distribution of the transient ground potential differences. In addition, when measuring the impulse impedance of a grounding grid, the length of the current leads should be very large, which requires a high-capacity impulse generator to suppress the influence of lead inductance on current waveform. In this paper, a test method is proposed for the transient characteristics of grounding grid with the current-return point located in the same grid. The feasibility of the method is illustrated by analyzing the ground impedance between the current injection point and the return point, longitudinal current of the grounding conductor, transient ground potential rise and transient ground potential difference. The effects of parameters such as soil resistivity, lightning waveform, size of the grounding grid, spacing and materials of the grid conductor are discussed to demonstrate that the method can be applied to most substations. Finally, the practicality of the method is verified by experiments in a 220 kVsubstation. [ABSTRACT FROM AUTHOR]

In this paper, a wind turbine service sustainability is achieved by assessing grounding grids under steady-state and lightning-based transient conditions. An effective grounding grid is designed concerning IEC61400-24 standard, where Taif city, Saudi Arabia is considered a farming place. However, high soil resistivity is a challenge during the design. To accomplish the study, apparent resistivities are measured using Wenner method, in the field. A framework of multi-layer soil modeling is performed using the Sunde model, and it is optimally solved using the genetic algorithm. Using the optimal stratified soil, the wind turbine grounding system is assessed considering grounding resistances, electric potentials, and step voltages. The break-point effect is evaluated considering the designed grounding system. Then, the lightning-based transient study is investigated for both the healthy grid and break-point considerations. COMSOL Multiphysics and ATP/EMTP were used to accomplish simulations and modeling. The results ensure the effectiveness design of the assessed grounding system.

Grounding grid configuration which, is key to its fault diagnosis, changes continuously with the extension in a substation. Furthermore, older substations grounding grid configurations are unknown. Existing literature regarding configuration detection mainly accounts for the magnetic field that required a gradient to locate the grounding conductor. The gradient of raw measurement in the substation vicinity enhances electromagnetic noise and distorts the results. Therefore, in this paper, we have developed a new algorithm, Configuration Detection of Grounding Grid (CDGG) based on the static electric field and the concept of ordered pairs to draw the configuration of the unknown grounding grid. Unlike, the practiced magnetic field, the electric field does not require a gradient. The maximum electric field value indicates the location of a grounding conductor. The connection between nodes is verified by measuring the electric field on the circle. Furthermore, the proposed algorithm also locates any diagonal conductor in the configuration. Mathematical reasoning and simulation results illustrate that our proposed algorithm is feasible to draw the configuration of the unknown grounding grid.

As an important part of substation, grounding grid is the main approach to release short-circuit current. Grounding grid is in the complex electromagnetic compund,and with increasely being operated, it is easily corroded for various reasons, resulting in short-circuit current not being discharged normally. It is difficult to detect the grounding grid without excavation, because it is generally buried underground. Therefore, it is very important to accurately detect the grounding grid without excavation. In this paper, a grounding grid detection method based on artificial intelligence hybrid algorithm is proposed. In order to verify the accuracy of the detection method, the grounding grid model is established by using electromagnetic transient simulation software ATP-EMTP. According to the ATP-EMTP simulation model, the node potential of each point of the grounding grid is detected as the reference object for verification. In order to remove the randomness of the simulation results, the average value of 20 tests was used as the corrosion diagnosis result. The results show that the missed diagnosis rate of the proposed in paper was 2.1%, which was reduced by 12.1%, 7.1% and 7.5% respectively compared with the other three algorithms. At the same time, the misdiagnosis is 2.1%, which is reduced by 10%, 6.2% and 12.9% respectively for the other three algorithms. In sum, the corrosion leakage diagnosis rate and misdiagnosis rate of the proposed artificial intelligence algorithm are lower than those of the other three optimization algorithms, and have higher accuracy and stability in corrosion diagnosis. [ABSTRACT FROM AUTHOR]

The grounding grid is the cornerstone for maintaining the safe operation of the power system. The grounding network acts as a concealed project, and its invisible characteristics make the defects difficult to be detected, which causes major safety hazards in the system. Thus accurate diagnosis of grounding grid corrosion is vital in electrical engineering. A diagnosis method for grounding grid corrosion based on branch voltage disturbance is proposed in this paper, which can judge the location and degree of corrosion through branch voltage disturbance before and after corrosion. Firstly, the sensitivity of branch voltage to branch resistance of the grounding grid is analyzed. Secondly, a diagnostic model based on branch voltage disturbance is established, and the corresponding regularity between peak voltage disturbance and the corrosion state of the grounding grid branch is developed. Finally, it is verified by experiments that this method can effectively diagnose the corrosion of the grounding grid.

It has been determined that the discharge of lightning current to ground through grounding grid results in high potential at the grounding grid and other nearby grounding grids, which is very destructive. In the present paper, based on artificially triggered lightning technology, the characteristics of the ground potential rise (GPR), the transient effect at the active grid under the transient impulse of lightning current was analyzed. The impulse grounding resistance is found to decrease for large input currents. On the other hand, for small input currents, it usually increases. In addition, the characteristics of the transfer potential of the passive grid which is located 40 m from the active grid were analyzed. It was shown that the peak value of the transfer potential at the passive grid was approximately 5.1% of the peak value of the ground potential at the active grid during the return stroke. The achievements made in this study may contribute toward the optimization of the simulation model.

Configuration of Grounding Grid is required for all currently proposed Fault Diagnosing methods of Grounding Grid if the configuration is unknown then Grounding Grid Configuration detection techniques are applied and all of these latest techniques further requires the oriented angle at which the grid is laid and if the orientation of the grid is unknown or incorrect then the calculated configuration will be misleading and incorrect and we will fail to diagnose the Grounding Grid Fault. In this paper Transient Electromagnetic Method approach is used for orientation detection of Unequally Spaced Grounding Grids which are categorized as complexed grids further classified as Unequally spaced grounding grids with a diagonal element at larger mesh, smaller mesh, or in both of these meshes. In TEM method Equivalent Resistivities and Magnetic Field Intensities are found at eight different points in a circular path of constant radius r to determine the size of meshes and the presence of conductors whether diagonal or not diagonal. Model Designing and Simulations are performed using COMSOL Multiphysics 5.4 software, values of Magnetic Field Intensities and EMF are derived from COMSOL Multiphysics 5.4 software and the EMF values are further called in a MATLAB code to run through a number of mathematical formulations and Equivalent Resistivity is obtained for all desired points. Obtained values of Equivalent Resistivity and Magnetic Field Intensities verifies the effectiveness of the proposed approach for orientation detection of complexed grounding grid.

Nondestructive testing of substation grounding grids is an issue that has increasing importance. The traditional EMI method transforms the condition of the undergrounding conductors to the surficial induced electric signal in the sensing coil. However, The EMI signals excited by multiple coexisted faults combining with other unknown noises surrounding the substation often cause the failure of detection. Therefore, the observed EMI signals rather complex and cannot be used directly. To address this problem, the separation of individual signatures from the mixture is posed as an SCBSS problem. To extract the induced signal, an EEMD-based EMI method is proposed. The desired signal is then reconstructed to visualize the structure of the grounding grids by a virtual instrument that consists of DAQ and digital signal processing modules. The numerical simulation and practical experiments are employed. The results show the proposed method can be used to effectively detect the topological structure of grounding grid in real substations' electromagnetic environment.

In this paper, a wind turbine service sustainability is achieved by assessing grounding grids under steady-state and lightning-based transient conditions. An effective grounding grid is designed concerning IEC61400-24 standard, where Taif city, Saudi Arabia is considered a farming place. However, high soil resistivity is a challenge during the design. To accomplish the study, apparent resistivities are measured using Wenner method, in the field. A framework of multi-layer soil modeling is performed using the Sunde model, and it is optimally solved using the genetic algorithm. Using the optimal stratified soil, the wind turbine grounding system is assessed considering grounding resistances, electric potentials, and step voltages. The break-point effect is evaluated considering the designed grounding system. Then, the lightning-based transient study is investigated for both the healthy grid and break-point considerations. COMSOL Multiphysics and ATP/EMTP were used to accomplish simulations and modeling. The results ensure the effectiveness design of the assessed grounding system. [ABSTRACT FROM AUTHOR]

Faults in electrified railway grounding grids can lead to significant surface potential rise, which threatens railway transportation and operation security. In order to efficiently diagnose the grounding status of the grounding grid and locate the fault location, this paper firstly presents the development of a mathematical model to reveal the earth surface potential distribution of grounding grids. Furthermore, a simulation model is built specifically for this study using CDEGS software to calculate the earth surface potential distribution of grounding grids under fault conditions. The simulation model has been used to validate the developed mathematical model by a comparison study. Finally, an intelligent algorithm based on grey incidence degree and fuzzy theory is proposed. This algorithm facilitates the fault condition diagnosis and the fault conductor position location. Using the fault condition data calculated by the simulation model, a few common grounding grids' fault conditions are diagnosed and located effectively by the proposed method. The results identify that the proposed method can ensure the safe operation of the traction substation. [ABSTRACT FROM AUTHOR]

A grounding grid plays the role of discharging current and balancing voltage to ensure the safety of the power system. However, soil corrosion can damage the grounding grid, which then can endanger the safe operation of power system. This paper reviewed recent research advances of soil corrosion of grounding grid. The cause, mechanism, types, and influencing factors of soil corrosion of grounding grids were summarized, and the corresponding detection technology and protective measures were also introduced. The paper pointed out that soil corrosion is a serious threat to the grounding grid system. Moreover, the impact mechanism of AC stray current, new corrosion detection technology, and better protective measures still need in-depth research.

The configuration is essential to diagnose the status of the grounding grid, but the orientation of the unknown grounding grid is ultimately required to diagnose its configuration explicitly. This paper presents a transient electromagnetic method (TEM) to determine grounding grid orientation without excavation. Unlike the existing pathological solutions, TEM does not enhance the surrounding electromagnetic environment. A secondary magnetic field as a consequence of induced eddy currents is subjected to inversion calculation. The orientation of the grounding grid is diagnosed from the equivalent resistivity distribution against the circle perimeter. High equivalent resistivity at a point on the circle implies the grounding grid conductor and vice versa. Furthermore, various mesh configurations including the presence of a diagonal branch and unequal mesh spacing are taken into account. Simulations are performed using COMSOL Multiphysics and MATLAB to verify the usefulness of the proposed method. [ABSTRACT FROM AUTHOR]

The grounding device plays performs the role of releasing a lightning current and a fault current in the power system, and the corrosion of the conductor will cause damage to the grounding body, which threatens the safe operation of the power system. The grounding grid corrosion detection technology and equipment guarantee the safe operation of the power system. This paper discusses the research status of grounding corrosion and topological detection in detail and introduces the basic principles, research difficulties and existing problems of the methods such as the electric network method, electromagnetic field method, electrochemical method, ultrasonic detection method and electromagnetic imaging method. The methods of electromagnetic imaging and time difference positioning proposed in recent years have been also discussed in detail. The paper points out that the application of grounding grid corrosion detection distance engineering still faces great challenges and that multi-disciplinary, multi-information fusion, new sensing technology, big data platforms and intelligent computing will be the trends to follow in research on grounding grid fault, corrosion detection and life prediction. [ABSTRACT FROM AUTHOR]

A grounding grid is essential to the lightning protection of power systems. This paper presents a modified partial element equivalent circuit method for predicting the transient behavior of the grounding grid. The frequency-dependent parameters of the grounding grid are obtained first by using the image method. Both modified nodal formulation and vector fitting techniques are applied to derive an extended equivalent network for time-domain simulation. In this method, the soil ionization effect is considered using a nonlinear resistance. The proposed method is verified with experimental results available in the literature. Finally, lightning transients in the grounding grid of a radio base station is presented. The ionization and propagation effects on grounding grid performance are discussed. [ABSTRACT FROM AUTHOR]

En este artículo, se estudia la resistencia de puesta a tierra en redes urbanas de distribución eléctrica de la ciudad de Copiapó (Chile) por medio de distribuciones de probabilidad, con el objetivo de evaluar el desempeño del diseño de las mallas que actualmente se utiliza en esta ciudad. El estudio está basado en una muestra de cuarenta y tres mediciones de resistencia de puesta a tierra. Se muestran los principales indicadores de estadística descriptiva para las mediciones de campo, se ajustan tres distribuciones de probabilidad a los datos de la muestra y se usan el criterio de información de Akaike (AIC) y el criterio de información Bayesiano (BIC) para elegir la distribución que mejor representa el comportamiento de los datos. Finalmente, usando el modelo seleccionado, se calculan algunas probabilidades para la resistencia de puesta a tierra y se entregan las principales conclusiones del trabajo.In this article, the grounding resistance in urban electrical distribution networks of the Copiapó city is studied. The estimation of mean value is calculated using continuous probability distributions. The aim of this study is to performance assessment of grounding grid design currently used in these networks. Forty-three grounding grids are used as sample. The main indices of descriptive statistics of field measurements are shown. Three continuous probability distribution models are fitted to the sample. For selecting the best model, the Akaike information criterion (AIC) and the Bayesian information criterion (BIC) are used. Finally, using the best model, some probabilities for the grounding resistance are calculated and the main conclusions are presented.

The configuration of grounding grids which are used to earth electrical substations could be equally or unequally spaced. Unequally spaced grids were introduced to improve the requirements of the grids such as grounding grid resistance (Rg), ground potential rise (GPR), maximum touch voltage (Et) and maximum step voltage (Es) values. Also, unequal spacing can reduce the cost of the grids and enhance the level of safety for people and equipments. In this paper two different approaches were used to determine the best possible configuration of grounding grid. These approaches based on sequential multiplicative and sequential power techniques.

A thin-wire model of conductors with arbitrary cross sections for a finite-difference time-domain (FDTD) method is proposed for the study of lightning transients in electrical systems. The proposed thin-wire model considers both the frequency-dependent characteristics of the wires and the influences of the surrounding media. The model represents a wire using four FDTD cells with an equivalent side length and modified material parameters. A rational equivalent circuit is added at the center edge of the FDTD cells to represent the internal impedance of the wire. An analytical formula for determining the equivalent side length and the modified material parameters of the FDTD cells are also presented. The proposed formula gives a new prospect to build the thin-wire model in FDTD. In this model, the equivalent side length can be set arbitrarily and much larger than the original wire, which can greatly reduce the computation time. Meanwhile, the method can be extended to the thin-wire structure with arbitrary cross sections. The model is verified with various measurements. Finally, a practical grounding grid of a substation with external water supply is analyzed. [ABSTRACT FROM AUTHOR]

Impulse performance of grounding grid is needed for lightning protection design of power system. This paper describes an impulse test facility established for the full-scale grounding grid (50 m long and 52.5 m wide) in a 110 kV substation. Test method is presented, including configuration of current injection and return point, measurement of potential rise and longitudinal current. Impulse test is carried out with 2.6/50 and 8/20  μs current waveform, and the maximum current amplitude is 4 kA. A Current Distribution, Electromagnetic fields, Grounding and Soil structure simulation for the tested grounding grid is also adopted. Impulse performance of full-scale grounding grid is affected by soil ionization and conductor inductance. There is steeper peak on the potential rise waveform near the injection point with shorter wave front current, which leads to more uneven potential rise distribution. Partial soil ionization could increase the current dispersing into the soil at partial area of the grounding grid, and the longitudinal current flowing to the next area decreases. These two factors pose a high potential difference hazard to the secondary equipment via the secondary cable. [ABSTRACT FROM AUTHOR]

For the safe and reliable operation of an electrical system, grounding grids are used. The current distribution in such grounding grid conductors is calculated by either an analytical or a numerical method. This paper presents a new method to obtain the current distribution in grounding grid conductors with and without vertical rods buried in two layers of soil. The two‐layer soil model has been simulated mathematically using two suitable values of resistivity. The computations of the current distribution have been based on the current for each segment of meshes. The investigation includes different meshes, such as one mesh, four meshes, nine meshes, and/or also more meshes. The calculation technique of current distribution is carried out to give all the mutual resistances with respect to (x,y,z) coordinates of each segment to solve the equation containing all segment currents of the meshes. The results in this paper give the current distribution for each segment of each mesh with and without the driving rods. The effect of vertical rods, which are connected to the horizontal grounding grid, on the current distribution and grounding resistance for different grounding grid dimensions and shapes has been studied. For increasing the flexibility of current distribution calculations of the grounding grids, the per‐unit system has been used in this paper. An experimental model to simulate the two‐layer soil model is presented for the validation of the calculated results. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Location and topology of substation grounding grids are critical for its regular tests and safe operation. Schematic drawing of the grounding grid is prone to getting lost or damaged. As excavation is costly and time consuming, locating substation grounding grid is important. This paper proposes a novel method to locate substation grounding grid by using the derivative method and the concept of locating a geometrical object in polar coordinate system. Due to rectangular structure of grounding grid, its location can also be determined from the location of its single branch. Simulation and experimental results verify that the proposed method is feasible and accurate to solve the inverse problem regarding the location of substation grounding grid. [ABSTRACT FROM AUTHOR]

The grounding device plays performs the role of releasing a lightning current and a fault current in the power system, and the corrosion of the conductor will cause damage to the grounding body, which threatens the safe operation of the power system. The grounding grid corrosion detection technology and equipment guarantee the safe operation of the power system. This paper discusses the research status of grounding corrosion and topological detection in detail and introduces the basic principles, research difficulties and existing problems of the methods such as the electric network method, electromagnetic field method, electrochemical method, ultrasonic detection method and electromagnetic imaging method. The methods of electromagnetic imaging and time difference positioning proposed in recent years have been also discussed in detail. The paper points out that the application of grounding grid corrosion detection distance engineering still faces great challenges and that multi-disciplinary, multi-information fusion, new sensing technology, big data platforms and intelligent computing will be the trends to follow in research on grounding grid fault, corrosion detection and life prediction.

The grounding grid is critical to the safety and stability of a power system. Corrosive cracking of the grounding conductor is the main cause of deterioration of grounding grid performance. Existing fault diagnosis methods for grounding grids are limited by the number and distribution of grounding leads, and some of them cannot be used for online detection. This paper proposes a grounding grid detection method based on magnetic source excitation. The measuring device consists of four coils, two horizontal excitation coils, and two vertical receiving coils. The secondary magnetic field signal is extracted from the primary field and the background field by properly positioning the coils, such that the measured signal can reflect the underground media more accurately. The measuring device of the method is portable, the measurement process is contactless with the grounding grid, and it is not limited by the grounding leads. Furthermore, it has a strong anti-interference ability and can realize online detection. It was proven by simulations and experiments that the proposed method has a higher measurement accuracy and stronger anti-interference ability when compared with existing methods. This paper also discusses the influence of various factors such as the number and the location of the breakpoints, the frequency of the excitation source, the soil resistivity, and stratification from the measurement data. It was proven that the method has high precision and a wide application range, and is important for guiding significance and reference value in engineering applications.

The grounding grid of a substation is important for the safety of substation equipment. Especially to address the difficulty of parameter design in the auxiliary anode system of a grounding grid, an algorithm is proposed that is an optimization algorithm for the auxiliary anode system of a grounding grid based on improved simulated annealing. The mathematical model of the auxiliary anode system is inferred from the mathematical model of cathodic protection. On that basis, the parameters of the finite element model are optimized with the improved simulated annealing algorithm, thereby the auxiliary anode system of a grounding grid with optimized parameters is structured. Then the algorithm is proven as valid through experiments. The precision of the optimized parameters is improved by about 1.55% with respect to the Variable Metric Method and the Genetic Algorithm, so it can provide a basis for parameter design in the auxiliary anode system of a grounding grid.

Optimizing the grounding grid configuration is an effective approach to improve the performance of grounding grid. On the other hand, configuration of grounding grid is necessary for some defect diagnosis method to detect the faults existing in grounding conductors. This paper employs the transient electromagnetic (TEM) method to draw the configuration of a substation grounding grid. The surface magnetic field is recorded by receiver coils above the grounding grid. Based on the regular distribution characteristics of a recorded magnetic field, the grounding conductor is accurately located from the curve of magnetic intensity. The complete process of configuration detection of the grounding grid is described in detail. After fast inversion calculation of the recorded magnetic field, the equivalent resistivity is obtained. The configuration of the grounding grid will be clearly and accurately shown in the contour map and three-dimensional (3-D) surface map of equivalent resistivity. Model study is performed, and a field test is also conducted. The results are in good agreement to demonstrate the effectiveness of TEM method for configuration detection of the substation grounding grid. [ABSTRACT FROM AUTHOR]

The corrosion diagnosis of grounding grid can locate the corroded branches and provide guidance for the maintenance and repair of the grounding grid. This paper proposed the electrical impedance tomography (EIT) method on the corrosion diagnosis of grounding grid and described how it works. Firstly, the inverse problem model of the electrical impedance tomography on grounding grid is developed. Secondly, in order to weaken the ill-posedness of the inverse problem, a Newton iterative algorithm with Tikhonov regularization is proposed to solve the problem. Then, due to the high resistivity contrast between the soli and steel and the large size of imaging region, this paper presents the method of soil-separation and block-diagnosis to accomplish these problems. Finally, field experiments were carried out to verify the effectiveness of the proposed method and the results show that the location and degree of the corrosion in the grounding grid can be easily judged from the imaging results.

The grounding grid is a key part of substation protection, which provides safety to personnel and equipment under normal as well as fault conditions. Currently, the topology of a grounding grid is determined by assuming that its orientation is parallel to the plane of earth. However, in practical scenarios, the assumed orientation may not coincide with the actual orientation of the grounding grid. Hence, currently employed methods for topology detection fails to produce the desired results. Therefore, accurate detection of grounding grid orientation is mandatory for measuring its topology accurately. In this paper, we propose a derivative method for orientation detection of grounding grid in high voltage substations. The proposed method is applicable to both equally and unequally spaced grounding grids. Furthermore, our method can also determine the orientation of grounding grid in the challenging case when a diagonal branch is present in the mesh. The proposed method is based on the fact that the distribution of magnetic flux density is perpendicular to the surface of the earth when a current is injected into the grid through a vertical conductor. Taking the third order derivative of the magnetic flux density, the main peak coinciding with the position of underground conductor is accurately obtained. Thus, the main peak describes the orientation of buried conductor of grounding grid. Simulations are performed using Comsol Multiphysics 5.0 to demonstrate the accuracy of the proposed method. Our results demonstrate that the proposed method calculate the orientation of grounding grid with high accuracy. We also investigate the effect of varying critical parameters of our method.

In this paper we propose a new formalism for analyzing the transient behavior of grounding systems associated to substation structures (Faraday-cage) under lightning strokesin unsettled regime. The protective device to study is formed of a guard filet connected to a grounding grid by simple conductors called down conductors. Our formalism is based on the resolution of the propagation equation in potential on 3D. The purpose of our proposition is the direct analyzing in time domain and simple implementation. We compare the results obtained by this new approach to results published in literature.

In this paper the influence of different soil models on step and touch voltages are presented. Soil resistivity is the basic characteristic of soil which affects a number of parameters (temperature, humidity, salt content). Basic methods of measuring soil resistivity presented in this paper are: Wenner method, Schlumberger method, General method, Driven rod (3-probe) method and the Dipole-Dipole method. Soil resistivity measurements are used to obtain an equivalent soil model (uniform model, two-layer horizontal model, multilayer horizontal model, vertical model and others). The CDEGS software package is used for computing GPR (Ground Potential Rise), touch and step voltage with several different soil models. The resulting effect of soil models on the grounding resistance, GPR at the surface, touch and step voltages are shown. The 3D spatial distribution and 2D presentation of all characteristic values for safety analysis are presented and plotted. [ABSTRACT FROM AUTHOR]

The condition of the substation grounding grid is vital for the safety of the people. Inadequate grounding may cause failures in major substation's equipment, as well as in control, metering and telecommunication equipment. Therefore, it is necessary to clearly identify damaged elements on grounding grid. This paper presents an approach to test the integrity of the grounding grid in a general framework of IEEE Std. 81-2012. More precisely, in order to locate damaged grounding riser(s) and/or grounding grid conductor(s), this paper is focused on novel unambiguous criteria for post-processing of raw-data collected from the measurements. In order to avoid the effect of power frequency interference on the measurement, we use DC test current of 100 A. The field test is described and discussed in details. The outcome of field test clearly shows the validity and feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

• The impact of premature failure of the grounding grid is studied. • Based on the smoothness of the epoxy insulator, the breakdown process is phased. • 2D cable joint models are built to describe the actual breakdown process. • The discharge-damage mechanism of joint insulation is proposed. The grounding grid on the outside of the epoxy insulator breaks under the long-term oxidative corrosion of moisture, fails prematurely, and may eventually develop into a breakdown failure. However, the impact of this process has not yet been discovered. In this paper, a 110 kV combined prefabricated cable joint breakdown fault is discussed. Through the inspection and comparative analysis of the faulty joint, it is speculated that the premature failure of the grounding grid causes the breakdown of the epoxy insulator. The fault process can be divided into the grounding failure stage and the insulation damage stage. In this paper, the corresponding two-dimensional electric field simulation calculation model is established, the fault development process is restored, and the possible effects of different stages is analyzed. The results show that due to the corrosive effect of moisture, when the grounding grid is broken, a floating potential will be generated on the surface of the epoxy insulator. With the expansion of the grounding failure range, the local field strength on the surface of the epoxy insulator is distorted, which will cause partial discharge. When the failure range is 220 mm, the electric field distortion of the joint reaches the maximum value of 23.3MV/m, which will destroy the insulation strength of the epoxy insulator and cause insulation breakdown, eventually leading to an accident. The research results point out the importance of the continuity of the grounding grid, and the improvement measure is proposed to reduce the occurrence of such accidents. The analysis method for cable joint failure case can provide a reference for dealing with similar accidents. [ABSTRACT FROM AUTHOR]

In this paper, three metaheuristic techniques have been developed to propose a safe and economic grounding system for the future power plant of Labreg situated in Khenchela City (400 km east of Algiers). The corresponding algorithms have been elaborated using particle swarm optimization (PSO), genetic algorithm optimization (GAO) and hybrid particle swarm genetic algorithm optimization (HPSGAO). The aim is to minimize the cost of the considered grounding system basing on the optimal decision of its construction and geometrical parameters in accordance with the security restrictions required by the ANSI/IEEE Standard 80-2000. A new mathematical model has been proposed for the cost function. This later includes the number of conductors, conductor dimension, grid depth, number of rods, length of rods, total area of excavation, and revetment. The results show that the HPSGAO technique presents lower values of the cost than those obtained using GAO and PSO methods. The good accordance between HPSGAO technique safety parameters and those of the CYMGrd code confirms the efficiency of the proposed algorithms. [ABSTRACT FROM PUBLISHER]