Kamal Kerroum

Generalized Form of Telegrapher's Equations for the Electromagnetic Field Coupling to Buried Wires of Finite Length

In this paper, a generalized form of telegraphers equations for electromagnetic field coupling to buried wires is derived. The presented approach is based on thin-wire antenna theory. The effect of a dissipative half-space is taken into account via the reflection/transmission coefficient approximation. The conductor losses can be taken into account via the surface impedance per unit length. The derived equations are treated numerically via the Galerkin-Bubnov indirect boundary element method. Numerical results are presented for induced current along the wire, and compared with transmission-line (TL) and modified TL (MTL) approximations, respectively, for the case of perfectly conducting electrode buried in a lossy medium. It is shown that the TL and MTL approximations can result in an inaccurate induced current distribution along the conductor at HFs and for shorter electrode lengths, respectively.

Transient Response of Straight Thin Wires Located at Different Heights Above a Ground Plane Using Antenna Theory and Transmission Line Approach

Transient electromagnetic field coupling to straight thin wires parallel to each other and located at different heights above a perfectly conducting or dielectric ground plane is analyzed using wire antenna theory and a transmission line method. The time-domain antenna theory formulation is based on a set of the space-time Hallen integral equations. The transmission line approximation is based on the corresponding time-domain Telegraphers equations. The space-time integral equations arising from the wire antenna theory are handled by the time-domain Galerkin-Bubnov scheme of the indirect boundary element method. The time-domain Telegraphers equations are solved using the finite-difference time-domain method. Time-domain numerical results obtained with both approaches are compared to the results computed via NEC 2 code combined with an inverse Fourier transform procedure. Some illustrative comparisons of results obtained by means of antenna theory and transmission line approach are presented throughout the paper.

Comparison of Matrix Pencil Extracted Features in Time Domain and in Frequency Domain for Radar Target Classification

Feature extraction is a challenging problem in radar target identification. In this paper, we propose a new approach of feature extraction by using Matrix Pencil Method in Frequency Domain (MPMFD). The proposed method takes into account not only the magnitude of the signal, but also its phase, so that all the physical characteristics of the target will be considered. With this method, the separation between the early time and the late time is not necessary. The proposed method is compared to Matrix Pencil Method in Time Domain (MPMTD). The methods are applied on UWB backscattered signal from three canonical targets (thin wire, sphere, and cylinder). MPMFD is applied on a complex field (real and imaginary parts of the signal). To the best of our knowledge, this comparison and the reconstruction of the complex electromagnetic field by MPMFD have not been done before. We show the effect of the two extraction methods on the accuracy of three different classifiers: Naive bayes (NB), K-Nearest Neighbor (K-NN), and Support Vector Machine (SVM). The results show that the accuracy of classification is better when using extracted features by MPMFD with SVM.

Comparison of Image and Transmission Line Models of Energized Horizontal Wire Above Two-Layer Soil

The paper presents comparison between two approximate models of energized horizontal thin-wire conductors above two-layer soil. The formulation is posed in frequency domain by using two approaches. The first one is based on quasi-static image theory within Mixed Potential Integral Equation. The second one is based on transmission line theory with approximation of per unit length parameters. The authors compare currents computed by the both approximate models of a center fed wire to establish the computation errors over a wide frequency range. The main objective is to validate the proposed image and transmission line models for various lengths of wire conductors, and various cases of low and high conductivities of two-layer soil. The verification of the results is done by comparison with exact model based on full-wave theory. Detailed parametric analysis clearly illustrate validity domain and problems when using both approximate models with respect to their use in practical EMC studies.

Electromagnetic field coupling to overhead wires: Comparison of wire antenna and transmission line model in the frequency and time domain

The paper deals with different approaches for the analysis of electromagnetic field coupling to overhead wires of finite length based on the wire antenna theory, and transmission line method (TLM). The formulation based on the wire antenna theory in the frequency domain is based on the corresponding Pocklington equation, while the time domain formulation is based on the space-time Hallen integral equation. Transmission line model is based on the frequency and time domain Telegraphers equations.. The integro-differential and integral realtionships arising from the wire antenna theory are numerically handled via the frequency and time domain Galerkin-Bubnov scheme of the Indirect Boundary Element Method (GB-1BEM), repectively. The transmission line equations are treated using the Finite Difference Time Domain (FDTD) Method. Some illustrative numerical results obtained via different approaches are presented in the paper.

A simplified approach to modeling the interaction between grounding grid and lightning stroke

In this work, a new approach for the modeling of the interaction between grounding grid and lightning stroke is described. We treat the case of direct and indirect effects of lightning strike. In the case of direct impact, we inject in point of grounding system a current with bi-exponential wave shape and we calculate the distribution of potentials and currents on the grid and the electromagnetic field it will emit. For the second case, we treat a problem of electromagnetic coupling, which is to calculate the induced currents that developed on the grounding grid when this later is illuminated by a lightning channel located in its vicinity. The presented model is validated by comparing the obtained results to the results arising from the full wave (antenna) model available in literature and to the results obtained by using NEC4 software. The principal advantage of the presented approach is the simplicity of the implementation providing a direct determination of the both current and potential distribution along the grounding grid and the related electromagnetic field in an arbitrary point in the air and/or soil, as well.

A new hybrid approach using time-domain reflectometry combined with wavelet and neural network for fault identification in wiring network

The modern power electric network is subject to insure more and more complicated functions; the main functions are transfer of energy and information. The faults in wiring cables constitute one of worst problems of power electric network. In practice, the combination of Time Domain Reflectometry (TDR) and wavelet transform is generally used to detect and localize the faults in electric network. Classically, the identification process based on the decomposition of fault signal on details and approximations using Discrete Wavelet Transform (DWT) build some errors both at fault position and in fault nature. For solving this problem a new and improved method which combines the time domain reflectometry, wavelet transform and neural network is proposed in this paper. First, the response of the transmission line is obtained using the Finite Difference Time Domain method (FDTD) applied to transmission line equations, then, the obtained results are analyzed with DWT. Finally, Neural Network method (NN) is applied to solve the inverse problem for reducing the error of fault location affecting the branches of electric network.

ON THE ROTATIONALLY-CYLINDRICAL MODEL OF THE HUMAN BODY EXPOSED TO ELF ELECTRIC FIELD

The paper presents an assessment of human exposure to extremely-low-frequency (ELF) electric fleld generated by a power line using the rotationally-cylindrical body model. The formulation is based on the Laplace type continuity equation. The induced current density in the three-dimensional (3D) model human body is obtained by solving the Laplace equation via the Finite element method (FEM). The main objective is to highlight some parameters in∞uencing the distribution of the induced current density, such as the ohmic contact between the feet and the soil due to the soles of the shoes, and the electrical parameters of the soil. Furthermore, the in∞uence of internal organs (the human model) to the induced current density distribution. The human body is represented by a homogeneous model and also by an inhomogeneous model composed of several organs namely brain, heart, lungs, liver and intestines, whose shapes were spheroid. The proposed model has been validated through comparison to either the experimental results or the theoretical results available in literature being computed by the aid of a homogeneous body model.

Modeling of the Direct Lightning Strike on a Towers Cascade Equipped with its Protections

In this paper, a direct time domain approach based on the corresponding transmission lines equations and Finite Difference Time Domain (FDTD) method is proposed to analyze a direct lightning strike to a cascade of transmission line towers. The proposed model deals with a real case of towers being connected by ground wires and equipped with grounding systems with different topologies, as well(vertical or horizontal conductor buried in the ground, crows feet in the ground...). In particular, this work realistically represents the tower geometry and accounts for the propagation phenomena along the tower and between the towers. The proposed direct time domain approach deals with rather complex electrical devices (towers, ground wires and grounding systems), but at the same time requires very low computational cost and also provides relatively simple implementation. Some illustrative computational examples related to some engineering applications are given in the paper.

Antenna mode currents and radiated emissions of in-door PLC line within wall structure

It is known that the total currents flowing in a given circuit may be decomposed into differential or transmission mode currents and common or antenna mode currents. The second ones are generally supposed to be the main source of emission problems related within PLC. In this paper the main objective of the authors is to analyze the frequency dependence of antenna mode currents in a PLC unbalanced circuit. The unbalance is a result of a changing the circuit from symmetrically to asymmetrically driven. Of interest is the relationship between the change of the amount of antenna mode currents due to source asymmetry and the effect on the radiated electric field. The numerical analysis is based on the full-wave theory that is solved by the method of moments. The studied theoretic example is a simple 5m long PLC line placed within a concrete wall structure.