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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.

A prerequisite for the proper and safe designing of a grounding system is the full knowledge of the ground structure in the terrain of installation. Through soil resistivity measurements, engineers are able to illustrate the ground profile, which constitutes the most significant parameter for the design of a grounding system and for determining the maximum permissible limits of step and touch voltages. This paper highlights the high importance and necessity for engineers to choose the proper measurement axes of soil resistivity in the terrain of interest and to choose suitable measurement depths, as well the combination of axes for the final determination of the ground profile. The variance of soil resistivity values, as a function of axis distance and the impact of axis placement on determining the uncertainty of measurements, is also analyzed in detail in this study. Furthermore, this work studies the value variance of step and touch voltages as a function of measurement axes, considering two- and three-layer soil models, based on soil resistivity field measurements performed at the university campus. Therefore, the proper and premeditated measurement of soil resistivity, particularly in anisotropic ground, is proved to be of major importance for the full designing of a safe grounding system.

This article covers the analysis of voltages induced on the conductors of a de-energized circuit of a multi-circuit, multi-voltage HVAC transmission line. As a result of the multiplied interactions between the circuits in such lines, the expected electrical shock currents (touch currents) to which a lineman performing live work on such a line may be exposed are determined. A number of supporting structures of three- and four-circuit lines with various degrees of geometric asymmetry are analyzed. Analyses have shown that in multi-circuit lines in which circuits of different voltages are carried on a common structure, despite the outage of one of the circuits, touch voltages and electrical shock currents (touch currents) exceeding the permissible values can be expected on its conductors, endangering the safety of the lineman. The arrangements of s in such lines that provide the smallest values of touch currents are indicated.

With the rising demand for electricity and the expansion of power generation facilities, grounding systems have become critical for ensuring human safety and equipment protection. This study employs the finite element method to model single- and double-layer grounding networks, evaluating their effectiveness in mitigating step and touch voltages. Findings reveal that, despite increased complexity and cost, the double-layer configuration does not significantly enhance ground resistance reduction or voltage distribution, indicating that the single-layer network remains a reliable and efficient solution.  Con el aumento de la demanda eléctrica y la expansión de las instalaciones de generación, los sistemas de puesta a tierra se han vuelto esenciales para garantizar la seguridad humana y la protección del equipo. Este estudio emplea el método de elementos finitos para modelar redes de puesta a tierra de una y dos capas, evaluando su eficacia en la mitigación de las tensiones de paso y de contacto. Los resultados muestran que, pese a su mayor complejidad y costo, la configuración de doble capa no mejora significativamente la reducción de la resistencia de tierra ni la distribución de voltaje, indicando que la red de capa única sigue siendo una solución confiable y eficiente.

Sweden has a very high and variable soil resistivity, making it difficult to ensure a consistently good connection to earth along the track. Booster Transformers (BTs) have been used to ensure that the current returns through the intended path and that stray currents are limited. The ability of BTs to control return currents is limited by their series impedance and by imperfect coupling. In this article, we make a detailed model of the BT system between two feed-in points and evaluate how well the BT system can contain stray currents at harmonic frequencies. The main contribution is that we demonstrate that harmonic currents are significantly less well contained by the BT system, and that the practice of allowing local grid connections to the railway earth system risks creating significant stray currents in the local grid, particularly at harmonic frequencies, but also that electrical safety may be compromised by the transmission of touch voltages to locations with a different soil resistivity than the rail bed.

Finding the optimum conductor’s pattern for unequally spaced grounding grids can be achieved by using empirical formulas or optimization techniques. Empirical formulas give an approximate solution depending on human experience and never cover the entire search space. On the other hand, the optimization techniques generally require a significant effort and time. To overcome the previous issues, this paper presents a closed-form solution based on optimized results. The main motivation behind this formula is the comprehensive study carried out by the authors to find optimum location of grounding grid conductors over different areas. In that work, particle swarm optimization technique (PSO) has been adapted with combined integration matrix method (CIMM) to facilitate the study. In this paper, the results obtained previously were summarized in the proposed formula. The proposed formula gives the optimum design of unequally grounding grids by specifying the conductor’s locations as percentage of the side length for square and rectangular shapes. As long as the side length and the number of conductors are given, the location of each conductor as a percentage of the side length can be obtained. The effect of adding driven rods and the stratified soil conditions on the results of the optimized design were investigated. The validity of the proposed closed-form solution was verified experimentally.

When a fault occurs in a power transmission system, voltages that are dangerous to people may occur. The aim of this work is to present the following method of protection: the use of protective foil installed at the appropriate depth around the transmission pole. Moreover, a procedure is presented for determining the optimal size of the protective film using a minimum number of finite element method calculations. In addition to the finite element method, evolutionary methods are used to determine the appropriate coefficients. Real earthing system data, earth data, and the fault current are obtained from the Slovenian system operator (ELES, d.o.o.) and used exclusively in the presented analyses. The results of determining the appropriate size of the protective foil for two transmission poles are presented, and the determination of the required breakthrough strength of the materials used is shown. The suitability of the proposed method is confirmed. This method is practical and useful when protection with protective foil is required, ensuring only as much as necessary is applied.

Introduction. Normalized parameters of the grounding system, such as touch voltage and resistance, are critically important for ensuring electrical safety and reliability of power plants and substations. The complexity of the multi-layered soil structure makes it difficult to determine mentioned parameters. This is due to the fact that real soils on the territory of energy facilities of Ukraine have three or more layers, and the specified parameters are determined by software with two-layer calculation models. Therefore, the need to provide multilayer geoelectric structures into equivalence two-layer models for practical application is an urgent task. Goal. Determination of the application limits of the multilayer soils equivalence method based on the calculating results analysis of the grounding system normalized parameters. Methodology. The study considered a three-layer model for four soil types (A, H, Q, K) common in Ukraine. The calculations were performed using the LiGro software package, which is based on the method of integro-differential equations, applied to the analytical solution of the problem of the electric field potential of a point current source in a three-layer conducting half-space. As a criterion for the possibility of applying the equivalence method, a relative error value of 10 % was chosen when determining the normalized parameters of a grounding system of the given topology and soil type. When determining the error, the calculation results in the original three-layer soil structure for the given topology of the grounding system were taken as the true value. The results show that the effectiveness of equivalent technique significantly depends on the type of soil and the area of the grounding system. In particular, for soil type A, replacing the upper and middle layers with the equivalent first layer (the lower layer with the second) provides a smaller error in the calculations of the grounding resistance than representing the upper layer as the first, and the middle and lower layers as the second equivalent layer. At the same time, there is a tendency for the error to decrease with increasing area of the object: from 225 m2 to 14400 m2, for the first case, the error decreased from –14.6 % to –2.6 %, and for the second case, it changed from –9.3 % to 14.6 %, respectively. Originality. For the first time, the results of the methodical error evaluation of the equivalence techniques of multilayered soils of different types when calculating the normalized parameters of grounding system are presented. Practical value. Determination of the conditions and limits of the use of the equivalence method when calculating the normalized parameters of grounding system by software complexes can be used in the design of new or reconstruction of existing energy facilities of Ukraine. References 20, tables 5, figures 4.

The article presents the analysis results of the effectiveness limitation of the step voltage by forming an electric field on the ground surface. For shaping the electric field, a method consisting of screens placed around the point of the earth current flow was used. The analysis was performed using an example of an MV/LV substation grounding system. This research was conducted applying a mathematical model of the grounding system and screens by means of the finite element method. The influence of metal, insulating screens and surface material on the step/touch voltage values for the considered grounding system was estimated. Most of the methods described can be applied in practice. In the opinion of the authors, the method of using screens made of insulating and conductive materials has not been sufficiently described in the literature. Moreover, in the available literature there is no in-depth analysis of the described electric field shaping methods.

The design of a compliant, safe, and reliable substation earth grid is not a straightforward process; in most cases, it requires some additional measures to be taken due to various constraints that differ from environment to environment, such as soil resistivity, a high fault level, a limited surface area, construction budget, etc. The IEEE Std 80-2013 proposes various refinement methods that can be applied to address different situations. For this study, the current limiting method, current diversion method, and touch and step voltage increment method were applied using the Electrical Transient Analysis Program (ETAP). A power system was designed, where a fault current generated by the supply transformers and back-fed by the power system’s motors was exported to the earth grid. Using this fault current, various simulations were conducted to assess the performance of the earth grid. The analysis results show that the application of the current limiting method using neutral earthing resistors has a great impact on the design of the earth grid as this method significantly reduces the fault current injected into the earth grid. Furthermore, by applying the current diversion method, the amount of fault current injected into the earth grid is reduced by a fair amount, which improves the performance of the earth grid. Lastly, increasing the tolerable limits of touch and step voltages by reducing the fault clearance times significantly improves the compliance of the earth grid as the clearance time is reduced. From this study, it is therefore concluded that, by implementing the refinement methods depending on the design requirements and feasibility of the application, one can improve the compliance state of an earth grid.