Search

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]

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]

This paper presents a novel computational methodology, based on the finite element technique, for the analysis of electromagnetic field due to system of arbitrarily positioned current-carrying conductors in horizontally stratified multilayer medium, having arbitrary number of layers with different characteristics (including air). Each soil layer is horizontally unbounded, homogenous and isotropic, whereas conductors can penetrate different layers and extend into the air. The effect of the stratified multilayer medium is taken into account by using the originally developed fixed image method. Complete electromagnetic coupling between grounding system conductors (satisfying thin-wire approximation) is taken into account, whereas attenuation and phase shift effects are approximated. The electric and magnetic field in stratified multilayer medium are computed from the scalar electric and vector magnetic potentials, using the said fixed image method and approximations to the attenuation and phase shift effects. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Grounding grids are buried underground to reduce the earth resistance and provide ways for overvoltage protection and current leakage. With regard to the safety evaluation and fault diagnosis of substations, it is vital to know the accurate earth parameters before detecting the fault sites of grounding grid in substations. The estimation of earth parameters is used to solve the inverse problem of calculating apparent resistivity using given earth parameters. First, complex image methods are used to solve the improper integration with the assistance of Prony's expansion which is utilized to calculate the coefficients for the Lipschitz's expansions in this article. Also, by considering the root mean square error and absolute error (AbsE), we focus on different aspects of the effectiveness of the estimation. The root mean square error between the measured and calculated apparent resistivity ( \documentclass{article}\usepackage{amsmath}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{amsfonts}\pagestyle{empty}\begin{document}$\rho^a_{\mathrm{md}}$ \end{document} and \documentclass{article}\usepackage{amsmath}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{amsfonts}\pagestyle{empty}\begin{document}$\rho^a_{\mathrm{cd}}$ \end{document}, respectively) is set up as the main objective function, and AbsE as a supplemental criterion for measuring the estimation. Afterwards, improved particle swarm optimization is adopted to minimize the objective function with a constraint function. Resulting from the outstanding global searching characteristics, accurate soil parameters are much easier to obtain. A method to artificially regulate the initial values is proposed in this article, and two cases are introduced to validate the effectiveness. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The transient grounding impedance of a gas-insulated switchgear (GIS) substation was investigated through measurements on a commercial 300-kV underground substation. Using the results, the transient impedance of the grounding grid was investigated. The attenuation factor of the propagation line composed of the outer surface of the GIS tank and the concrete floor was also evaluated. The validity of EMTP analysis of surge phenomena in the GIS grounding system was confirmed. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 70–77, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10214 [ABSTRACT FROM AUTHOR]

In the simulation of electromagnetic fields produced by a point source located in multilayer media, the conventional image method requires an infinite number of images, while the method of complex images only needs a few ones to get an accurate solution. Based on the method of complex images, an approach for simulating grounding systems in multilayer soils is introduced in this paper, and the corresponding Green functions are derived. Software for simulating grounding systems in up to six-layer soils has been developed, and the grounding systems with any complicated structure can be located anywhere in multilayer earth models. Copyright © 1999 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]