Electromagnetic Field Coupling to Overhead Wire Configurations: Antenna Model versus Transmission Line Approach

The paper deals with two different approaches for the analysis of electromagnetic field coupling to finite length overhead wire: the wire antenna theory (AT) and the transmission line (TL) method. The analysis is carried out in the frequency and time domain, respectively. Within the frequency domain analysis the wire antenna formulation deals with the corresponding set of Pocklington integrodifferential equation, while the transmission line model uses the telegrapher's equations. The set of Pocklington equations is solved via the Galerkin-Bubnov scheme of the Indirect Boundary Element Method (GB-IBEM), while the telegrapher’s equations are treated using the chain matrix method and the modal equation to derive per-unit-length parameters. For the case of the time domain analysis AT model uses the space-time Hallen integral equation set, while TL approach deals with the time domain version of the telegrapher’s equations. Hallen equations are handled via time domain version of GB-IBEM, while time domain telegrapher’s equations are solved by using Finite Difference Time Domain (FDTD) method. Many illustrative computational examples for the frequency and time domain response, respectively, for several configurations of overhead wires, obtained via different approaches, are given in this paper

Induced Disturbance in Power Network by Lightning

In this work the transient analysis of a power network excited by indirect lightning is performed directly in time domain. Using the FDTD, we calculate induced currents and voltages in each node for a three-phase power network. The topological analysis of the network where each element (power line and lumped charge) is considered, allows deducing the matrix equation. In this electrical network matrix, power lines are represented by line equations, junctions and extremities nodes by Kirchhoff laws. The electromagnetic field emitted by lightning is represented in the second member of this matrix equation. The frequency dependence of the line parameters is taken in account while using time domain convolution

Transient Magnetic Field of Energized Buried Grid

A new approach is adopted in this paper for modeling the transient magnetic field, radiated by buried grid under lightning strokes. This approach summarizes each of three methods: analytical formula, based on electrical dipole theory for determining radiated magnetic field in infinite conductive medium, modified images theory for taking into account the interface in the half space, and transmission line approach for determining the longitudinal and leakage currents. The model can be used to predict the transient characteristic of grounding systems because, it can calculate magnetic field in any points of interest, it is sufficiently accurate, time efficient, and easy to apply

Elektormagnetska kompatibilnost kod zrakom izoliranih transformatorskih stanica

In this work, transient coupling between the bus bars of the Air Insulation Substation (AIS) and the control cable located at its proximity is analyzed. The present study accounts for the real complex geometry of the bus bars and the finite conductivity of the soil. A time domain formulation of the problem is proposed in this work. The direct time domain formulation based on the use of Transmission Line (TL) theory and the Finite Difference Time Domain (FDTD) solution method. The excitations are given in the form of the localized current or voltage generator, respectively, and related electrical field radiated by bus bars. To ensure the electromagnetic compatibility (EMC) requirements the current induced in the transmission cable is analyzed by means of the Pencil Method that will allow one to identify the dominant frequencies in the interference signal. Various illustrative examples are given in the paper.U ovom radu analizira se tranzijentna sprega između sabirnica zrakom izoliranih transformatorskih stanica i kontrolnog kabela u njenoj blizini. Ovom analizom uzima se obzir složena geometrija sabirnica i konačna vodljivost tla. Direktna vremenska formulacija zasniva se na teoriji prijenosnih linija i metodi konačnih diferencija u vremenskom području. Pobude su dane u vidu lokaliziranih strujnih, donosno naponskih generator i odgovarajućeg električnog polja kojeg zrače sabirnice. Da bi se osigurali zahtjevi elektromagnetske kompatibilnosti struja inducirana u prijenosnoj liniji analizira se primjenom Pencil Method koja omogućava identifikaciju dominantnih frekvencija u interferencijskom signalu.Razni ilustrativni primjeri se obrađuju u radu

Computation of SAR in Human Eye and Pregnant Woman Using Different Simulation Tools

Electromagnetic modeling of large scale problems arising from complex geometries, such as the human body or the specific organ, is generally undertaken by numerical methods implemented in simulation software packages. The structures involving high discretization density (mainly based on Magnetic Resonance Imaging and handled by Finite Difference Time Domain method) consume tremendously high computational cost. On the other hand, oversimplified numerical models may result in significantly less accuracy. The aim of this work was to investigate how detailed numerical model could be created using standard personal computer. Two rather complex cases of exposure were analyzed: human eye and pregnant woman exposed to radiofrequency electromagnetic radiation. The SAR distribution, peak localized 10g-averaged SAR and volume-averaged SAR in these models were determined using two software packages based on different numerical methods: FEKO software based on Finite Element Method and SEMCAD X software based on Finite Difference Time Domain method. The obtained results were compared to the results arising from other scientific studies which included the models of different complexity solved by different numerical methods

Tranzijentni odziv uzemljivačkog sustava u dvoslojnom tlu primjenom teorije prijenosnih linija

The present work deals with modeling of the transient behavior of grounding systems in the presence of layered media. A simple and efficient Transmission Line (TL) model featuring the use of the Finite Difference Time Domain (FDTD) is proposed. The proposed approach easily accounts for the influence of semi-infinite media (soil or air) and imposes conditions at the interfaces. The TL model is verified through the direct solution of the Maxwell\u27s equations in the time domain by means of the FDTD method. Some illustrative computational examples addressing some engineering applications stemming from industry are given in the paper.U radu se razmatra modeliranje tranzijentnog odziva uzemljivačkog sustav au prisutnosti slojevitih sredina. Predložen je jednostavan i efikasan model prijenosne linije uz upotrebu metode prijenosnih linija u vremenskom području. U okviru predloženog pristupa lako se uzima u obzir utjecaj polubeskonačnih sredina (tlo ili zrak) te postavljaju uvjeti na granici sredina. Model prijenosne linije verificira se direktnim rješenjem Maxwellovih jednadžbi u vremenskom području primjenom metode konačnog diferencija u vremenskom području. U radu se daju neki ilustrativni računalni primjeri koji se odnose na neke inženjerske primjene proizašle iz prakse

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: Naïve 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

Synthese analytique des convertisseurs statiques par la methode de conservation de la puissance instantanee: application a la determination des harmoniques des courants d'entree

SIGLEINIST T 72965 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc