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This paper presents an online method to monitor the conditions of substation grounding grid. The proposed method utilizes phase-to-ground faults occurring in downstream feeders as test current sources and the neutral of a specially selected feeder as the electrode for GPR (ground potential rise) measurement. The measured fault currents and GPRs are then used to estimate substation grounding grid impedance. The method, once established, can monitor the grounding grid impedance continuously and automatically, and the trend of the impedance change can be observed. As a result, the proposed method can yield much more reliable information on the substation grounding conditions. The method also overcomes many disadvantages of the offline methods. The proposed idea, algorithm, and hardware setup are described in the paper. Factors contributing to measurement errors are investigated in detail.

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).

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.

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.

The variation in soil structure has a great infleunce on the grounding grid performance. This influnce can be measured in terms of ground resistance, touch and step potentials. The addition of driven rods 10 the grid significantly affects the grounding grid performance. This paper presents a comprehensive experimental study for the influence of adding driven rods on the performance of grounding grids. The study is applied on three constructed scale models. The models have been performed to simulate a single-, double- and triple-layer soils. A comparison between results obtained experimentally and that computed by mathematical equations is introduced.

It is important to ensure that a grounding system is designed with a low magnitude of earth resistance, so the protection system can divert the large fault current to earth effectively. The performances and protection level of a grounding system need to be acknowledged as the condition of soil structure changes with different soil characteristics. At present, there is a lack of systematic guide or standards for grounding grid designs that consider non-uniform soil and its impact on the grounding systems. By computing the grid safety threshold parameters consisting of the grid impedance, step, and touch voltages, a comparison has been made between uniform soil and two-layer soil models. Where the competence and level of safety of the grounding systems depend on the soil attributes, the significant impact of various soil conditions is seen. The evaluations on performance and safety assessment in two-layer soil conditions hold the novelty and originality as there is no such comparison and discussion have been made to date. These comparisons would help in forecasting the behavior and safety of the grounding system in various soil environments, which would provide engineers with additional expertise to design an effective and secure grounding system. This research would contribute to the existing body of knowledge by differentiating and predicting the performance of a grounding system when the characteristics of the soil differ significantly from uniform soil as most of the standards and guidelines only consider uniform soil while designing a grounding system, owing to its complexity at the site.

To balance the potential distribution on the surface of a substation, an equal spacing arrangement of the grounding grid conductors is not an economical solution. The implementable solution is an unequal placement of its constituent elements. The design methodologies of such a configuration are complex and require computer-assisted numerical analysis. This paper proposes and validates a very simple method, based on an arithmetic progression, of arranging the conductors of the grounding grid that guarantees the reduction of touch and step voltages, ensures the efficiency of the material used and has no limitations on its applicability for atypical substation surfaces (too large or too small), respectively for few or many parallel conductors. To certify the method, the proposed algorithm is analyzed, through the CYMGRD Substation Grounding Program, and compared to the technologies currently applied, for the substation grounding grid presented as an example in the IEEE Guide for Safety in AC Substation Grounding 80™- 2013 standard.

The analysis of adjacent grounding systems under lightning currents which is responsible for many safety problems to human beings and damages to devices is very important. In this study, the behaviours of such grounding grids under lightning conditions which are not well documented in the literature are analysed using the multi-conductor transmission line method in a two-layer soil model. To achieve this goal, the expressions related to the study of a single grounding grid extracted from the recent study of the authors are developed to be appropriate to the analysis of adjacent grounding systems under lightning currents. Also, through the representation of the connectivity matrix, the analysis of the adjacent grounding grids with any size and degree of complexity is facilitated. Furthermore, the behaviours of the adjacent grounding grids under different lightning and soil characteristics are examined and some conclusions are derived.

This study examines the sustainability of uniform as well as an optimal grounding grid (GG) design for the microgrid (MG), in terms of variations in the top layer (TL), middle layer (ML), and bottom layer (BL) soil resistivities ( ρ 1 , ρ 2 , and ρ 3 , respectively) along with change in a thickness of TL and ML. GG design is highly dependent on ρ 2 , as it helps in determining the density of conductors at grid extremities. With an increase in ρ 2 , touch voltage (TV) crosses its tolerable limit, but step voltage (SV) remains within its limit. However, with a simultaneous increase in the thickness of ML (MLT), SV also crosses its limit. For ρ 2 higher than ρ 3 , with an increase in MLT, TV, and SV increase, while in the reverse case, they decrease. For the given MLT, ρ 3 is crucial in determining GG burial depth. Validation of results is done by comparing them with the IEEE standard. Also, the optimal compression ratio of GG with an increase in MLT is analysed. TVs can be reduced to a great extent, with the application of distinctive methods of earthing (TT-GG system, TN-S-GG system, and TN-C-S-GG system) in MG. This study also reveals that an increase in GG resistance leads to a reduction in TV.

This article investigates the impacts of electric potential (EP) and electromagnetic fields (EMF) on human health, especially for those living or working near a distribution system, as a co...

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.

Transient electromagnetic (TEM) method is a reliable means of non-destructive testing for fault diagnosis of grounding grid in substation. In view of the small transmitter loop of the TEM system and many measuring points and survey lines of grounding grid detection in substation. This study presents a fast solution to TEM apparent resistivity imaging for grounding grid detection using artificial neural networks. The input -output mapping relation of neural network is established based on TEM response characteristics of the grounding grid. The built network could map the recorded TEM data of grounding grid detection and quickly obtain the resistivity image. The proposed method offers accuracy and fast computation for the resistivity imaging of grounding grid. Feasibility and technical attractiveness of the proposed method in fast imaging of apparent resistivity is investigated with the measurement of grounding grids in the actual substations. It can be used in real time so that the recorded TEM data in substation can be calculated without re-training, which avoids time-consuming inversion computation. The rapid processing of massive data and submitting the detection results of the grounding grid to customers rapidly and in real time, which is expectation for a modern power industry.

The grounding grid is an important part of ensuring the safety of power plants and substations, and its performance is directly related to the safety of people, equipment and power grids. After the grounding grid is running, due to the concealment of the project, it lacks sufficient technical means to evaluate it after it is put into operation, which has caused many difficulties for equipment operation, personnel safety and grounding grid maintenance. In order to solve the above problems, this paper uses CDEGS software to simplify the modeling of the grounding grid of a substation, and evaluates the performance of the grounding grid by analyzing the soil resistance layered model, touch voltage, step voltage and other parameters of the grounding grid, and give an optimization plan.

Based on the actual measured soil resistivity in a substation, this paper uses CDEGS to calculate and analyze the effects of deep well grounding, oblique well grounding, and small well grounding on improving the grounding performance of the grounding grid. Through the comparison of main parameters such as grounding resistance, ground potential rise, touch voltage and step voltage, it can be known: The oblique well grounding can play the role of a deep well grounding, and it can also effectively expand the area of the grounding grid without the need for land acquisition, and the mutual shielding effect of the oblique grounding electrode is much smaller than that of the deep grounding electrode; The small well grounding is more effective in terms of the effect of the touch voltage at the edge of the substation.

This paper gives the different grounding mat design modifications and the impact on the design parameters of these modifications. Different modifications in different cases like case 1: grounding mat design without earth electrodes, case 2: grounding mat design with the electrodes at the corner of mat, case 3: grounding mat design with compression ratio without earth electrode, and case 4: grounding mat design with compression ratio and earth electrodes have been applied with the application of ETAP 16.0.0 version software. The primary framework of the grounding mat solidly depends upon, \( R_{g} \), \( V_{\text{touch}} \), \( V_{\text{step}} \), and ground potential rise (GPR). These quantities are of great concern for safety of any grounding system. Here, our main concern is to minimize the design quantities by inserting electrodes and by changing the compression ratio to meet the standard safety regulations annunciated in various guidelines and standards. Here, in this paper, homogeneous soil model is considered for designing the grounding mat.

Stray current, as a special current, is common in the earth, and it will have a certain impact on the grounding grid of the power system. Based on CDEGS modeling, this paper studies the distribution of stray current and its influencing factors. In addition, the stray current in the soil not only causes corrosion to buried metals, but also affects the cathodic protection system of buried metals to varying degrees. It is proved through simulation that a certain level of stray current will have a serious impact on the sacrificial anode cathodic protection method, but the external current cathodic protection method has little effect. Therefore, it is recommended to use the external current cathodic protection method in the area of stray current interference. Combined with an engineering example in a certain area, a corresponding external current cathodic protection scheme is designed according to the analysis of the factors affecting the stray current, which greatly reduces the corrosion rate.

In order to ensure the safe and stable operation of the substation, it is necessary to test and evaluate the substation grounding grid. In the actual measurement process, since the overhead ground wire is difficult to disconnect from the ground network, in order to obtain accurate measurement results, it is necessary to consider the influence of the shunt phenomenon on the grounding resistance measurement of the grounding network. In recent years, the resistance measurement method with short lead wire has gained wide attention due to the advantages brought by its shorter measurement leads. Based on the backward measurement method with short lead wire, this paper considers the influence of the shunt coefficient on its measurement results, proposes a correction formula through theoretical derivation, and proposes an improved method of it, which is verified by simulation. The improved method proposed in this paper improves its accuracy while preserving advantages of the original method, and it has certain significance for the measurement of large-scale grounding grids.

As referred to the safety of people, the metallic fence of a substation is an object of special care. The substation fence is subject to a potential rise as well as to direct contact with people and animals, which is a hazardous situation. The connection of the fence to the substations grounding grid, the sectioning of the fence through isolated parts and the design of a specific fence grounding system are then necessary items for a well-designed project. This paper presents the procedure for calculating the potential rise in a metallic fence, also a report of good fence designing practices, verifying such procedure with an example from the literature.

High resistivity soil may cause serious corrosion of substation grounding grid. The cathodic polarization curve and electrochemical impedance spectroscopy (EIS) of grounding grid metal at open circuit potential and different cathodic polarization potential were measured by electrochemical method. The method to determine the optimal cathodic protection potential (OCPP) of grounding grid in high resistivity soil was established. The result showed that the OCPP of Q235 steel was about -850 mV (vs. SCE), and the method was verified by immersion weight loss test. It is simple and feasible to use electrochemical method to study OCPP for cathodic protection of substation grounding grid, which is of great significance to prevent the corrosion of grounding grid, extend the service life of grounding grid and ensure the safe operation of grounding device.

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.

Buried depth of grounding grids is one of the important factors to determine the grounding performance in substations, however, the real buried depth of grounding grids is changed and unknown due to the drawing loss and backfill during the reconstruction of the grounding grids. This paper proposes a derivative-based method to detect the buried depth of different metal conductors. First, the theoretical basis for the derivative-based method to detect the buried depth is described, and an example calculation on buried depth detection according to the magnetic derivation characteristic is carried out for a single conductor case. The results indicate that the main-side-peaks characteristic of the derivative method can determine the buried depth of metal conductor effectively. Then, the analysis of grounding grids is carried out to verify its validation in grounding grid buried depth detection, and results indicate that the method is effective in the cases of magnetic field superimposing, different buried depths of grounding grid, and nonuniform distribution of current in grounding grid. Finally, the experimental results prove that the derivative method works well with low error.

This paper assesses the transient distribution of potentials along a grounding grid subjected to currents representative of first and subsequent strokes. It is shown that the transient non-uniform distribution of potential along the grounding system may lead to the flow of impulsive current between pieces of equipment grounded at distinct points. The methodology presented in this paper is useful in determining engineering actions to reduce the risks of electromagnetic disturbances propagation due to uneven potential distribution along grounding grids. Este trabalho avalia a distribuição transiente de potenciais ao longo de uma rede de aterramento submetida a correntes representativas do primeiro curso e subsequentes. Mostra-se que a distribuição não uniforme transitória de potencial ao longo do sistema de aterramento pode levar ao fluxo de corrente impulsiva entre equipamentos aterrados em pontos distintos. A metodologia apresentada neste artigo é útil na determinação de ações de engenharia para reduzir os riscos de propagação de distúrbios eletromagnéticos devido à distribuição desigual de potencial ao longo das redes de aterramento.

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.

The article is devoted to the measurement of stray currents in the ground on the electric substation located near a DC railway. Stray currents have a significantly destructive effect on metal underground structures. Most of the researches consider cables and pipelines for various purposes as such underground structures. In this article, attention is paid to grounding grids, as they are also subject to corrosion by stray currents. The article describes the method measuring and the results of stray currents distribution in the ground at the substation.

Substation design that refers to IEEE Standard 80–2000 can be carried out through manual calculation. Considering that there are lot of data involved used and also repeated calculations, it will be very difficult and requires high accuracy. Therefore, a computer-based computing system is needed to solve this problem. This paper discusses an application modelling of LabViewgraphical user interface to provide convenience in designing the substation grounding grid. Some options have been developed such as grounding grid resistance calculation method, conductor diameters determination, grounding grid selection with ground rod and without ground rod and weight body. The effect of any changes in design can be known directly and compared with limit of the touch voltage and the step voltage allowed. For validation, the model used data from Std. 80–2000 and compared with some design model already existed. As a result of this application, grounding grid design process will be easy, more accurate, and faster.

The ground potential will rise abnormally when impulse current injects into grounding grid if a converter substation is struck by lightning or there exist short-circuit faults. Transient ground potential rise (TGPR) could couple to the cable core wire through conductive and near-field coupling ways and it will invade the secondary system eventually. Taking those two coupling ways into consideration, this paper builds a simulation model describing the technisim on how TGPR couples to the secondary cables in an UHVDC converter substation and searches for the best grounding way for suppressing disturbance voltage in secondary cables’ cores caused by TGPR. Through simulation and test, for a single cable harness with armor double-ended grounded, we propose that cable’s shielding sheath should be grounded only in protecting cabin. For a four-segment cable, we find the best grounding way is that for the harness segment between protecting cabin and terminal box, we should guarantee armor double-ended in both sides while shielding sheath be grounded only in protecting cabin, for the segment between terminal box and operating cabinet, we should guarantee armor double-ended in both ends while shielding sheath be grounded only in terminal box, what’s more, the armor and sheath among operating cabinets should be grounded only in phase B’s cabinet.

The low-voltage distribution system of thermal power plants has a large auxiliary power load and is vulnerable to electromagnetic influence, so its lightning protection is relatively complex. This paper takes Xishui Substation as the research object, and uses CDEGS software to build its buildings and grounding grid model, and calculates the shunt of lightning current in branch conductors, indoor magnetic field distribution and grounding grid potential distribution of thermal power plants when lightning strikes buildings. The results show that the shunt coefficient of the thermal power plant buildings basically meets the specification requirements. The lightning that strikes buildings will not cause harm to indoor equipment near the middle. Lightning flowing through buildings and leaking into the ground will threaten its low-voltage distribution system with ground potential counterattack. This provides data basis for electromagnetic safety assessment of low-voltage distribution system in thermal power plants, and is of great significance for improving reliable operation of low-voltage distribution system in thermal power plants.

This study presents the comparative analysis of three grounding grid configurations to find the optimum grid design in terms of safety parameters. Square grid, rectangular grid and L-shape grid, buried in two-layer soil model are taken in this study. Same grounding area is considered to design three different configurations of grounding grid. Effect of different grid designs, shapes and dimensions on grounding system performance is noticed. Equal and unequal spaced grounding grids for each shape are designed and it is found that unequally spaced rectangular grid gives better results than other considered designs. Study shows that rectangular grid has minimum value of grounding system resistance, grounding potential rise and mesh voltage in comparison of square and L-shape grid. ANSI/IEEE standard 80–2000 are used to designing the grids and all safety constraints are followed as mentioned in the slandered. Good agreements are found with unequal spaced rectangular grounding grid in comparison of square and L-shape grid. Two-layer soil structure is considered in the analysis. Vertical rods are placed at the periphery of the grid.

In order to solve the impact of test point offset on the grounding network corrosion fault diagnosis results, Simulate offset conditions using PSCAD, Comparative analysis of fault diagnosis results of fully measurable branches. Find the law that implies it and propose a method of calculating the test points at different offset levels. According to the method, the original large-change sensitivity nonlinear fault diagnosis mathematical model and the hybrid particle swarm optimization algorithm are improved. Simulation experiments show that the improved fault diagnosis algorithm is accurate and effective for solving the grounding grid corrosion diagnosis problem of test point offset.

The corrosion condition of the grounding grid of the converter station is very important to ensure the safety and stability of the power system. From the perspective of the leakage current of the converter station equipment, the circuit model of the leakage current in the DC field of the converter station is proposed; According to the leakage current characteristics, the DC field of the converter station is divided into the high-voltage side and the neutral-pole side area; According to the actual situation of the converter station, a measurement and analysis platform suitable for the leakage current of the converter station equipment is built; Through field test, the leakage current of each area equipment is measured and analyzed, and the distribution characteristics of equipment leakage current in different areas are summarized; According to the measurement data, the areas and equipment types that should be focused on corrosion problems are proposed.

With the continuous development of high-speed railways, more and more electronic equipment is introduced into high-speed railway traction substations, and the grounding grid is an important facility to ensure the normal operation of electrified railways and the safety of people and equipment in the station. The safety performance evaluation of the grounding grid of high-speed railway traction substation is essential for the design of the grounding engineering. In this study, The safety performance of the grounding grid wasevaluated by a method of moment under a power frequency grounding fault and the lightning strike of the substation. The results show that while the grounding impedance of the traditional evaluation standard grounding grid meets the requirements, the contact voltage under the grounding grid power frequency grounding fault and the mesh potential difference under the lightning strike do not meet the safety standard.

The lightning impulse behavior of substation grounding grids plays a very important role in lightning protection of substations and the grounding design of the grounding grid around the down leads has great influence on it. This paper analyzed the lightning impulse behavior of substation grounding grids with different grounding designs around the down lead, including the connection points, local refinement and layout of vertical grounding poles around down leads. Results showed that special designs around down leads including multi-point connection, local refinement and vertical grounding poles could improve the transient behavior of substation grounding grid. Meanwhile only increasing the number of vertical grounding poles cannot improve the transient behavior significantly.

Considering urban substations ground grid diagnosis, some real-physical constraints result in measurement process challenges: 1) limited length between electrodes used to measure the equivalent impedance of the grounding system; 2) to determine the current that flows from ground grid conductors to the earth; and 3) to determine the grid resistance. In this scenario, an adequate diagnosis of the safety offered by the ground grid under test when a ground fault occurs is not a trivial task. This article describes a methodology that allows a reliable diagnosis regarding the safety provided by a substation ground grid. The methodology is applied to the parameters obtained in performed field tests. The method has two steps. First, the fall-of-potential method with reduced distances between electrodes is used to determine the equivalent impedance of the grounding system. Then, the ground current is obtained. In both stages, optimization techniques are applied to the specific equations that govern the phenomenon under investigation. Comparative case studies considering real-life data illustrate the effectiveness of the method.

Today with increase in use of microgrid, appropriate grounding design is needed for it. In this paper it is done by considering different grounding shapes for the MG. For this purpose, paper evaluates the performances of triangular, rectangular, square, L shape and T shape grounding design considering uniform and two layer soil structure. Influence of diverse designs on safety parameters such as touch voltage and step voltage are examined. Investigation is done with the help of ETAP based finite element method and for its authentification, results obtained by it are substantiated with analytical results obtained through IEEE standard 80-2013. As per the results obtained, triangular shape performs better. Also, this paper reveals the touch and step potential profiles for different shapes.

As one of the important equipment to ensure the normal operation of substation, the performance of grounding grid has been highly concerned. In recent years, researchers propose that the theory of electromagnetic induction can be used to diagnose and identify the corrosion fault of substation grounding grid. In this paper, a fault classification model based on LS-SVM optimized by PSO is proposed to identify the corrosion fault of grounding grid. Firstly, the wavelet packet transform principle is used to filter the original data, and the wavelet packet energy is used to construct the fault eigenvalue as the input of the fault classification model. Based on LS-SVM, a corrosion fault classification model is constructed, and particle swarm optimization method is used to optimize the parameters of the model, which solves the problem of traditional SVM parameter optimization. Through the practical application in substation, the model proposed in this paper can identify the corrosion of grounding grid conductor without excavation and power failure, which provides an effective scheme for engineering application.

대지의 접지 시스템 설치는 안전성과 전기 기기의 올바른 작동을 위해 필수적이며, 대지 파라미터, 특히 토양의 저항률은 대지 접지 시스템 설계에서 결정되어야 한다. 토양의 저항률을 측정하기 위한 가장 흔한 방법은 Wenner의 4전극 방법이 있으며, 이 방법은 1차원의 저항률을 얻기 위하여 가변 전극 간격을 갖는 큰 측정 세트가 요구되어 번거롭고, 시간소모가 많으며 비용이 많이 든다. 전기 저항 단층촬영법은 저비용이며 빠른 측정이 가능하다는 장점 때문에 토양의 저항률 분포를 추정하기 위해 적용될 수 있다. 전기 저항 단층은 관심지역에 놓인 전극에서 얻은 측정데이터를 사용하여 토양 저항률 분포를 특성화한다. 이때 전기 단층 촬영법의 역문제는 비선형성이 강하여 저항률 분포를 추정하기 위하여 Tikhonov 조정 방법을 갖는 반복적 Gauss-Newton 방법을 사용한다. 다양한 시뮬레이션을 수행하여 3차원 토양의 저항률 분포를 추정하는데 전기 저항 단층 촬영법은 유용한 성능을 제공하고 있음을 확인하였다.

The condition of thesubstationgrounding grid is vital for the safety of the people. Inadequate grounding may cause failures in majorsubstation'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 100A. The field test is described and discussed in details. The outcome of field test clearly shows the validity and feasibility of the proposed approach.

In the intelligent substation, the shell of the secondary equipment is connected to the ground grid locally. When the short circuit fault current is injected into the grounding grid to cause the ground potential rise, the potential difference between the two points of the grounding grid will affect the normal operation of the secondary equipment. In this paper, aiming at the grounding grid of a 220kV substation, the grounding impedance, ground potential rise and ground potential difference between galvanized flat steel and copper grounding grid are calculated by using CDEGS software. The results show that the copper ground grid has a significant effect on reducing the potential difference of the ground grid.

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.