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

Multi-spectral palmprint recognition based on oriented multiscale log-Gabor filters

Among several palmprint recognition methods proposed recently, coding-based approaches using multi-spectral palmprint images are attractive owing to their high recognition rates. Aiming to further improve the performance of these approaches, this paper presents a novel multi-spectral palmprint recognition approach based on oriented multiscale log-Gabor filters. The proposed method aims to enhance the recognition performances by proposing novel solutions at three stages of the recognition process. Inspired by the bitwise competitive coding, the feature extraction employs a multi-resolution log-Gabor filtering where the final feature map is composed of the winning codes of the lowest filters’ bank response. The matching process employs a bitwise Hamming distance and Kullback–Leibler divergence as novel metrics to enable an efficient capture of the intra- and inter-similarities between palmprint feature maps. Finally, the decision stage is carried pout using a fusion of the scores generated from different spectral bands to reduce overlapping. In addition, a fusion of the feature maps through two proposed novel feature fusion techniques to allow us to eliminate the inherent redundancy of the features of neighboring spectral bands is also proposed. The experimental results obtained using the multi-spectral palmprint database MS-PolyU have shown that the proposed method achieves high accuracy in mono-spectral and multi-spectral recognition performances for both verification and identification modes; and also outperforms the state-of-the-art methods

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

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

Caractérisation numérique de l'environnement électromagnétique transitoire des postes aériens hautes tension

Our research work focused on the digital characterization of the electromagnetic environment of a high-voltage airmail station with its lines:- transient radiation from a substation following an internal high-voltage operation- radiation of homopolar currents in the ground, earthing network, following an accidental fault (short circuit) or a lightning strike.The motivation of this work is the knowledge of the electromagnetic impact of the elements of the station on the remote control devices and measures specific to the network as well as on the environment (natural, industrial and residential).This quantification, by calculation, led us to model fairly complex radiating aerial topologies. The calculation of the radiated fields is carried out with the approximation of the thin wires, starting from the formalism which consists in calculating the transient currents by the laws of Kirchhof and / or by resolution of the equations of the telegraphists and the field by the equations of Maxwell.Nos travaux de recherche ont porté sur la caractérisation numérique de l'environnement électromagnétique d'un poste aérien haute tension muni de ses lignes :- rayonnement transitoire d'un poste suite à une manoeuvre haute tension interne- rayonnement des courants homopolaires dans le sol, réseau de mise à la terre, suite à un défaut accidentel (court circuit) ou à un impact de foudre.La motivation de ce travail est la connaissance de l'impact électromagnétique des éléments du poste sur les dispositifs de télécommande et de mesures propres au réseau ainsi que sur l'environnement (naturel, industriel et résidentiel).Cette quantification, par le calcul, nous a conduit à modéliser des topologies rayonnantes aériennes assez complexes. Le calcul des champs rayonnés est réalisé avec l'approximation des fils minces, à partir du formalisme qui consiste à calculer les courants transitoires par les lois de Kirchhof et/ou par résolution des équations des télégraphistes et le champ par les équations de Maxwell

FDTD Analysis of Nonuniform Transmission Lines Network under Incident Field Excitation

In this paper, a new model for analyzing nonuniform multiconductor transmission lines network in time domain is considered. The proposed model is based on the transmission line theory and the finite-difference time-domain (FDTD) algorithm, it allows obtaining induced currents and voltages directly on the all nodes (junctions and extremities). For this objective, and using a mathematical formulation based on the topological analysis of a network, we deduce a linear equation system which resolution leads directly to the induced quantities

Caractérisation d'une grille de mise à la terre par une équation de diffusion

Cet article a été rédigé conjointement avec l'équipe CEM de l'université de JIJEL en Algérie dans le cadre d'un contrat de recherche internationa