Search

The soil characterization is one of the major prerequisites in grounding system studies. Along with an adequate measurement procedure and a reliable field data processing, they are responsible for the success in the design and the installation of grounding grids in electrical power systems. In this frame of reference, the purpose of this work is to present an embracing investigation combining in-situ measuring data from soil resistivity and geological survey, supported by the Wenner method and standard penetration test (SPT). The study is focused on investigating the differences in the apparent soil resistivity interpretation, provided by distinct approaches, identifying the one that better correlates with SPT. Furthermore, a geoelectrical and geotechnical soil characterization is in-depth evaluated, culminating in the derivations among soil resistivity, moisture content, and its mechanical properties. The study has a particular application, but not restricted, to electrical substations design, in which a proper soil modeling and representation are mandatory. The obtained results are promising serving as a foundation for further investigation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Provides information on a study which examined the forces that appear in tumor region when a direct current (DC) flows in it. Information on the DC current therapy; Mathematical model used; Solution technique; Discussion of findings.

Focuses on the application of Bio-Electric Circuits Model (BECM) concepts which can destroy cancer cells. Treatment of cancer using BECM; Thermal effects caused by application of the direct current (dc) in cancer area; Lesion criteria.

This article presents a methodology to calculate grounding potentials in adjacent electrodes present in high-voltage substations subjected to a short-circuit current dissipated in the main grid. The contribution of the technique is the consideration of the coupling by the soil among electrodes taking into account a two-layer soil and irregular geometry of the conductors. This problem is of special concern due to the presence of passers-by near metallic fences, not directly connected to the grounding grid, whose potentials usually have not been evaluated. In this context, the article presents a general analytical formulation aiming to estimate the potential in multiple electrodes, leading to a possible risk to human beings close to the substation. Sensitivity studies are performed in order to evaluate the effect of the soil resistivity and the distance from the faulted grid and the coupled electrode. A practical application in a substation grounding system is discussed. Finally, a huge grounding system is evaluated in order to verify the robustness of the proposed formulation. [ABSTRACT FROM AUTHOR]

This paper presents the development of an analytical formulation for estimating the potential on the soil surface, caused by electric current calculated on a grounding conductor. The formulation has a great significance in its use in conjunction with 1-D numerical methods, which are not able to determine such potentials directly. The proposed study focuses on lightning surges considering the frequency dependence of the soil properties. First, the subject is introduced emphasizing important aspects related to the analysis and representation of grounding systems against lightning. Afterward, the proposed analytical formulation is introduced with a focus on the computational implementation of the transmission line modeling method in 1-D. Simulations were carried out considering a typical horizontal electrode used as grounding in the power electric system. The formulation was validated by comparing the results with the solution based on the electromagnetic model (CDEGS Software), which is considered the most stringent for the solution of full Maxwell equations due to their minimum approaches. The results demonstrate that the generalized formulation presents good accuracy, contributing to an improved representation of grounding systems based on numerical techniques in 1-D. [ABSTRACT FROM AUTHOR]

This paper presents an extended methodology based on the transmission line modeling method (TLM) aiming at a soil ionization representation for the simulation of grounding systems. This natural phenomenon can be represented by considering the variation of the conductive components present in the TLM circuit. The proposed analytical formulation is introduced with a focus on the computational implementation of the TLM method in one dimension. The method is not subject to divergent solutions, being numerically stable and the methodology can be incorporated into a general algorithm irrespective of the soil properties or characteristics of the grounding electrode and lightning surge. [ABSTRACT FROM AUTHOR]