Layers Of Different Conductivity Research Articles

Analytical Approach of three-dimensional Flawed Multilayered Structure for EC Inspection

This article is devoted to the development of two current source models for the analysis of 3D electromagnetic phenomena in a conductive part of spherical geometry based on the second-order magnetic vector potential method for eddy current nondestructive testing (ECNDT). The first model, for a homogeneous single-layer sphere, allows the analytical calculation of all electromagnetic quantities in the charge. The second allows to treat in addition to the three-dimensional aspect of the problem, the heterogeneity of the charge (with several layers of different conductivities). An investigations using a multifrequency system have shown better results in detection of small cracks. The observations take about the calculation of normalized impedance based on dissipate energy and Joule losses in conductive material.

Accurate Impedance Calculation for Underground and Submarine Power Cables Using MoM-SO and a Multilayer Ground Model

An accurate knowledge of the per-unit length impedance of power cables is necessary to correctly predict electromagnetic transients in power systems. In particular, skin, proximity, and ground return effects must be properly estimated. In many applications, the medium that surrounds the cable is not uniform and can consist of multiple layers of different conductivity, such as dry and wet soil, water, or air. We introduce a multilayer ground model for the recently-proposed MoM-SO method, suitable to accurately predict ground return effects in such scenarios. The proposed technique precisely accounts for skin, proximity, ground and tunnel effects, and is applicable to a variety of cable configurations, including underground and submarine cables. Numerical results show that the proposed method is more accurate than analytic formulas typically employed for transient analyses, and delivers an accuracy comparable to the finite element method (FEM). With respect to FEM, however, MoM-SO is over 1000 times faster, and can calculate the impedance of a submarine cable inside a three-layer medium in 0.10~s per frequency point.

Non-destructive assessment of ZnO:Al window layers in advanced Cu(In,Ga)Se2photovoltaic technologies

The increasing importance of the Cu(In,Ga)Se2 based thin films photovoltaic industry claims for the development of new assessment and monitoring tools to answer the needs existing in the improvement of the control of the processes involved in the production of solar cells modules. In this frame, a strong interest has been given to the development methodologies for the assessment of the CIGS absorber, nevertheless advanced optical tools for the characterization of the other layers in the solar cells are still missing. In this work, we report a non-destructive optical methodology based on resonant Raman concepts that has been developed for the characterization of Al doped ZnO layers (AZO) that are used as window layer in Cu(In,Ga)Se2 solar cells. Doping the ZnO layer with Al leads to the presence of a characteristic defect induced band at 510 cm−1 spectral region. The correlation of the relative intensity of this band with the resistivity of the layers provides a fast and reliable tool for their electrical monitoring. Analysis of solar cells fabricated with layers of different conductivities has allowed demonstration at cell level of the proposed methodology for the determination of efficiency losses related to degradation of the resistivity of the AZO layers.

Temperature distribution along an outdoor insulator subjected to different pollution levels

The appearance of dry bands on polluted insulator surfaces may cause the ignition of electrical arcs, which in turn give rise to tracking and erosion, or may elongate until they bridge the electrodes causing flashover. Efficient models able to predict the occurrence of such a severe problem are of paramount importance for the engineer involved in the design of power line insulation. The present paper concerns the evaluation of the temperature distribution along the surface of an outdoor insulator subjected to pollution of different severity in order to predict dry band formation. The proposed numerical procedure, based on the joint solution of Maxwell equations in their quasi-static formulation and thermal equations, has been applied to study the case of a suspension cap-and-pin glass insulator, covered with pollution layers of different conductivity and thickness. The dependence of the conductivity of the layer on the temperature has been taken into account properly. The influence of uniform and nonuniform pollution distribution on the temperature profile is discussed for an applied sinusoidal power frequency voltage.

Underground imaging by frequency‐domain electromagnetic migration

A new method of the resistivity imaging based on frequency‐domain electromagnetic migration is developed. Electromagnetic (EM) migration involves downward diffusion of observed EM fields whose time flow has been reversed. Unlike downward analytical continuation, migration is a stable procedure that accurately restores the phase of the upgoing field inside the Earth. This method is indented for the processing and interpretation of EM data collected for both TE and TM modes of plane‐wave excitation. Until recently, the method could be applied only for determining the position of anomalous structures and for finding interfaces between layers of different conductivity. There were no well developed approaches to the resistivity imaging, which is the key problem in the inversion of EM data. We provide a novel approach to determining not only the position of anomalous structures but their resistivity as well. The main difficulty in the practical realization of this approach is determining the background resistivity distribution for migration. We discuss the method of the solution of this problem based on differential transformation of apparent resistivity curves. The final goal of migration is to provide a first order interpretation using a computational effort equivalent to a forward modeling calculation.

Step Potentials and Body Currents Near Grounds in Two-Layer Earth

The equations customarily used in safety calculations for grounding electrodes assume that soil conductivity does not vary with depth. A more realistic model assumes that the soil consists of two horizontal layers of different conductivity. This may occur, for example, if a thin surface layer consists of wet soil, thawed soil, or concrete, and a thick layer of underlying soil is frozen, or consists of rock or dry soil. Such conditions markedly change the step voltage, contact resistance, and body current a creature on the surface will experience in the vicinity of a buried ground electrode. Equations are presented for voltage, voltage gradient (step voltage), contact resistance, body current, and electrode resistance in the vicinity of a ground electrode in the shape of a long buried wire in a two-layered earth. Graphs are also presented to give a quantitative and qualitative understanding of the effect of such layering on step voltage and body current.

The Polarization of Micropulsations and Geo-electric Structure

Summary A study is made of how electromagnetic induction in crustal conductivity anomalies affects the observed polarization characteristics of micro- pulsations. Use is made of a new linear technique of modelling conductivity anomalies in the Earth. This technique allows any curved interface between two layers of different conductivity to be modelled by using Fourier composition of solutions for a sinusoidal interface. Two particular models are studied, one representing a sedimentary basin on the surface and the other a buried fault. It is found that the polarization characteristics of long-period pulsations (>100 s) are only slightly affected by both models. However, although the buried anomaly has little effect on the polarization of medium- and short-period pulsations (< 100 s), anomalies near or on the surface can change their polarization characteristics considerably. It is concluded that more care should be taken in the siting of geomagnetic observatories and in the interpretation of micropulsation data.

Use of geomagnetic storms in magnetotelluric interpretation

Consideration of electromagnetic diffusion into a conducting medium leads to the observation that individual frequency components of transient electromagnetic fields can be considered to penetrate the medium with a velocity that depends on frequency. In addition to being attenuated as they propagate, these components are reflected at the interfaces between layers of different conductivity. An interpretive procedure based on these observations was developed [Towle, 1971] after Wait [1954] first noticed that resolution of the conducting layers in the transient response of a two-layered conducting medium was possible.

Water movement in layered soils-a simulation model.

The simulation model is written in "continuous system modelling Program" and is applied to ploughed and unplowed soils with layers of different conductivity. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Mutual impedance of circuits with return in a horizontally stratified earth

During recent years considerable attention has been given to investigation of the mutual impedance between two circuits with earth return. The problem is of importance. On a knowledge of this coupling depends the predetermination of the telephone interference which may arise from earth-fault currents or residual currents of harmonic frequency in power and traction systems. Theoretical formulae, which have been confirmed by field experiments, are available for its calculation where the earth can be considered to be homogeneous and of uniform conductivity. Experience has shown, however, that this condition is not always fulfilled. Where it is not, the assumption of an earth structure consisting of two horizontal layers of different conductivity would in nearly all cases give the accuracy required for engineering purposes. Curves have been prepared to facilitate calculation of the mutual impedance in the case of stratification of this type. They give an equivalent conductivity which, when introduced into the formulae relating to a homogeneous earth, will yield a mutual impedance equal in magnitude to that resulting from the given stratified conditions.