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Metamaterials (MTMs) based on a periodic array of resonant coils have been shown to behave as μ-negative (MNG), enabling the focusing of magnetic flux. The phenomenon has been deployed by designers to boost the efficiency of many inductively coupled systems, such as magnetic resonance imaging, underwater and underground communications, and charging base stations (CBS) for consumer electronics and implanted devices. However, due to their dependency on high-Q unit cells, linear MNG-like MTMs have limited bandwidth, restricting their use in many applications, notably in near-field simultaneous wireless information and power transmission (NF-SWIPT) systems. To improve the tight constraints of the amplitude-bandwidth trade-off of artificial magnetic lenses, this paper presents a theoretical analysis of nonlinear MTMs based on a lattice of Duffing resonators (DRs). Additionally, it introduces a criterium for the quantification and evaluation of the amplitude-bandwidth enhancement. The analytical results are based on a circuit model and further verified by numerical simulations using commercial software. The preliminary findings in this paper open up possibilities for nonlinear MTM lenses and can be applied to enhance the linear amplitude-bandwidth limit.

This paper proposes a non-contact method for fault location in transmission lines, which is based on magnetic fields produced by current signals measured using magnetoresistive sensors installed only at transmission line terminals, under the phase conductors of the first transmission tower at both terminals or at the substations portals. The proposed method uses the Extended Kalman filter to process these measurements and is based on a travelling wave approach in order to perform the fault localization. This paper also describes the implementation and testing of the method, firstly introducing its overview, followed by an analysis of the magnetic fields produced by the current signals, as well as considerations on their measurement; secondly, detailing the Extended Kalman filter and the travelling wave approach; and, finally, presenting the results of the method with regards to simulations built using EMTP/ATP to evaluate its robustness under different conditions varying the fault resistance, fault inception angle, phases involved and fault location. The results indicate that the proposed method is robust and accurate.

The growing use of electrical and electronic technologies has intensified the electromagnetic environment at the same time as new technologies tend to be more susceptible to electromagnetic interference (EMI). This is a major concern for the application of electrical and electronic equipment in safety-related systems since faults and malfunctioning caused by EMI can affect human and environmental safety. In this context, the achievement of functional safety regarding electromagnetic disturbances, known as electromagnetic resilience, is mandatory to prevent the occurrence of incidents and accidents. The process to reach electromagnetic resilience is based on many steps, in which the risk assessment is one of high importance. Although many risk assessment techniques have been studied and general rules for their selection have been developed, little effort has been done to establish a method to evaluate the suitability of risk assessment techniques for electromagnetic resilience. This paper introduces a proposal for a framework to select risk assessment techniques suitable for electromagnetic resilience. The definition of criteria is based on the literature research concerning the fundamental difficulties encountered in the electromagnetic resilience field. The formulation of the selection problem and the comparison analysis between the selected risk assessment are performed using the Analytical Network Process (ANP) method. To illustrate the methodology, it is performed an application comparing two well-known risk assessment methods: failure mode and effect analysis (FMEA) and failure tree analysis (FTA).

Power converters are an essential part of modern power systems, giving flexibility to the power transportation and allowing the insertion of a wide range of different energy sources. One drawback of the converters is that the supraharmonic conducted emissions introduced by them can compromise the stability of these systems through electromagnetic interference (EMI). Electromagnetic compatibility (EMC) filters are used to prevent such problems. Nevertheless, these filters are designed to respect standards based on measurements in conditions considerably different from real applications. Particularly, if a converter is connected to electrically long cables its conducted emissions may be amplified by the resonance phenomenon. The method described in this paper allows the definition of a range for the filters input impedances where the conducted emissions in a long cable will not be amplified beyond established levels. In some cases the method allows the visualization of three-dimensional surfaces indicating the magnitude, frequency and position of the resonance phenomenon. In the general case these surfaces are defined on higher dimensions and can be analyzed with deterministic optimization algorithms. The originality of this paper resides in the generalized analysis of the resonance phenomenon, that it is based on frequency-dependent cable parameters and applies to unbalanced systems.

International audience; In the electromagnetic compatibility behavior of power electronic converters, parasitic magnetic couplings between components are one of the main causes of dysfunctions or poor filtering. These couplings may be either conducted or near-field interferences. To handle interaction problems, full knowledge of these magnetic couplings is essential. This paper is an overview of the work on near magnetic field interference undertaken in the last 15 years by the International Maxwell Laboratory. This paper details a predictive method that accurately and efficiently calculates near magnetic field coupling between two sources. The method uses near-field multipolar expansion in spherical harmonics of electromagnetic sources to determine close magnetic coupling between two sources from their equivalent models. This paper also shows how theoretical developments of large loop antennas have evolved from the van Veen antenna, a model with only two degrees of freedom, to a more complex model in terms of degrees, order, and types of harmonics. In parallel, it describes developments in the measurement method that provides input to the theoretical model. To illustrate how the research has evolved, we discuss coupling between two complex sources to assess the accuracy of this predictive method.

WOS:000599506500051; International audience; A novel numerical analysis to characterize and to visualize the resonance behavior in a long cable is proposed. The resonance-due maximum amplification, and the frequency and position to which the maximum occurs, are represented in function of the load connected to the cable terminal in a 3-D plot here denominated "resonance surface response." This analysis is based on a white box modeling and allows the design of protective measures against the resonance phenomenon, such as filter design, protection against cross-talk, adequate voltage insulation choice, etc. One of these applications is exemplified: the design of an output filter for a power converter connected to a long cable, from which the results are compared to a classical design of the same filter to highlight the advantages and demonstrate the robustness of the proposed technique.

Neste trabalho são apresentados o desenvolvimento e construção de um sistema de microondas para espectroscopia paramagnética eletrônica em baixa freqüência (bandas L e S). Basicamente o sistema é composto de um oscilador que opera na faixa de 1,0 a 2,0 GHZ, uma cavidade do tipo Bridged Loop-Gap, acopladores direcionais, circuladores, atenuadores, detetor, sistemas de controle automático de freqüência CAF e pré-amplificador. Todo o arranjo compõe uma ponte de microondas que é acoplada à unidade de processamento e registro do espectrômetro VARIAN (E-109) do Laboratório do grupo de biofísica do IFQSC. No sistema apresentado os estágios de amplificação de baixo ruído, circuito de CAF, pré-amplificador e sistema ressonante foram desenvolvidos e implantados localmente. A conveniência em se utilizar um espectrômetro de RPE em baixa freqüência é permitir o estudo de amostras que apresentam características espectrais vindas das interações hiperfinas e superhiperfinas parcialmente resolvidas em freqüências mais altas. Também é possível obter-se parâmetros de energia de campo zero de sistemas de spin com S &#62 1 se o sistema puder ser tratado por métodos aproximativos em banda X. Um exemplo utilizando o íon Cr3+ no garnet CGGG é mostrado neste trabalho In this work a microwave bridge for electron paramagnetic resonance spectroscopy hás been developed. The system is suitable for operation at low frequency, basically L and S-band. It is composed of an oscilator with a 1.0 to 2.0 GHz bandwith, a Bridged loop-gap resonator, directional couplers, circulators, attenuators, reverse diode detector, AFC sub-system and a pré-amplifier. All these modules are assembled to a constitute a microwave bridge, which is coupled to the processing and register unit of the VARIAN E-109 EPR spectometer of the Biophysics Laboratory at IFQSC. The low-noise amplifier, AFC sub-system, pre-amplifier and the Bridged Loop-Gap resonator have been entirely developed in this work. The advantage in the use of the low frequency EPR spectometer is that it allows the study of samples which present paramagnetics structures that are obscured by g-strain at high frequency (X, Q band). These structures come out from hiperfine and superhiperfine poorly resolved in the high frequency range that could be conventienly resolved at low frequency. It is also possible, to obtain the zero field splitting parameters in spin systems with S &#62 1, if a perturbative approximation is useful, comparing the spectre in X and L band. One example of this new approad using Cr3+ as impurity in the CGGG garnet is presented.

The perspectivist virtue theory developed by Sosa requires two elements for a belief to be correct. First, the belief must be formed from a reliable ability or competence; second, the believer must have a higher order belief according to which he forms his beliefs from reliable abilities or competences. This conception faces Jason Boehr's accusation of negligence for not allowing character traits to have a place in the justification project. I will show Sosa's reply to this accusation and I propose to follow Audi and show that character traits, though interesting and desirable, play only an auxiliary role in the justification of beliefs and are inessential for knowledge.

WOS:000487045600005; International audience; A complete modeling technique for unshielded power cables is proposed. The focus is on applications where the resonancephenomena take place in electrically long cables and is originated from periodic excitation, such as power converters.The resonance problems caused by switching converters tend to become more common with the advent of wide band gapsemiconductors. This paper includes a new experimental protocol specific for unshielded power cable parameter identificationin a wide frequency band, from DC up to medium frequencies (tens of MHz), with an impedance analyzer. It also introduces afrequency-domain simulation tool with conversion to the time domain, via the Fourier series. This frequency-domain modelingis straightforward, and its accuracy depends only on the accuracy of the cable parameter identification.

This article presents a hybrid computational method to address the datalink characteristics of an Unmanned Aerial Vehicle (UAV) relay. It uses the 3D far-field gain data from the antennas (UAV and ground station), separately computed or based on available measurements as inputs, and then applies the 2-Ray propagation model, taking into consideration the ground permittivity and the respective antenna heights. By doing so, different numerical approaches cover the two different physical scales. Since the installed antennas (i.e. antennas considered placed on the UAV fuselage) performances are considered, a higher reliability can be achieved with the covered procedure, at lower costs when compared to field measurements. Results for different example scenarios are presented and discussed.

This paper presents a method for equivalent emission source determination by application of LLAs (Large Loop Antennas). A review of different types of LLAs is carried out and their characteristics regarding emission source evaluation are emphasized. A hybrid technic is applied for obtaining the electric fields based on previous measurement of magnetic fields combined with an analytical and numerical approach. This methodology is proposed as an alternative to face the constraints concerning to the near electric fields measurements and calculations.

International audience; This paper considers the resonance phenomena observed on cables connected to power converters, evaluating theoretically and experimentally the voltage amplification due to resonance on these cables. The experimental study was effectuated on cables typically used on industrial applications. Factors restricting resonance-due amplifications are considered, as well as the conditions under which resonance issues may rise in such systems.

This paper presents a methodology for low-voltage AC surge protective device (SPD) coordination. As motivation, the required nuclear plant reliability and safety criteria, in which the surge protection coordination can assume an important role, are emphasized. Due to the characteristics of the protection system, and the surge phenomena, an iterative methodology is applied. The SPD selection and specifications are based on the equipment immunity level, insulation and on SPD characteristics, like absorbed energy. Some results are presented and discussed, showing the suitability of the proposed methodology.

A metamaterial-based insulator is proposed for highly compact MIMO-systems. In previous work, the proposed insulator has been demonstrated to reduce efficiently the coupling at PEC boundaries between two very close antennas on a common ground plane. The present study concentrates on the effects of this insulator on the antenna radiation pattern. The chosen operating frequency is 2.4 GHz considering that it is a usual frequency for many indoor wireless applications. The theoretical results are supported by numerical simulations.

An analysis of analytic tower models is proposed for simulation of electromagnetic transients in transmission lines supported by towers up to 300 m height. A careful analysis is required for emergent technologies in transmission systems composed of line sections supported by tall towers, with more than 200 m, as recently constructed in the Brazilian Amazon region and across the Yangtze River in China. Usually, conventional towers are modeled using simplistic geometrical forms and analytic formulations. This paper proposes an evaluation of well-established analytic models for representation of transmission towers with more than 50 m height. The analysis is carried out based on reference values of surge impedance obtained by using the Finite Element Method – FEM for towers up to 300 m height and then compared to existing analytic models based on the tower representation by cylindrical form. The reference model is developed using a FEM-based multiphysics software, where the tower can be drawn following the original design of its steel structure. The comparison between these two different modeling techniques is presented as a function of the tower height, surge impedance calculation and electromagnetic transient simulations in the time domain. From the proposed analysis, the most adequate tower models can be determined for analysis of the lightning performance in power transmission systems composed of tall line sections.

An important way to decrease the EMC issue is to predict near-field coupling between components. The using of their electromagnetic equivalent model in spherical multipolar expansion, allow to calculate the near-field magnetic coupling. The method cannot be properly applied when the sources are too close. In this paper we use a spheroidal expansion system, propose to solve the problem which enable to extend the efficiency of the method when the sources are close.

International audience; The electromagnetic interference between the electronic systems or their components influences the performance of the systems. For that reason, it is important to model these interferences in order to optimize the position of the systems or their components. In this paper, a method is proposed to construct the equivalent emission source models of systems. The proposed method is based on the multipolar expansion by representing the radiated emission of generic structures in a spherical reference . Some results are presented illustrating our method.

International audience; This paper presents a hybrid mono/multiobjective optimization approach based on numerical, statistical, and fitness evaluation concerning the conductor positions in a transmission line excitation chamber (TLEC). The field profile and the related indexes of merit, as well as statistical ones, regarding the working volumes (WVs) are used to evaluate the chamber configuration performance. The compromise between WV and $E$ -field, constrained by the $E$ -field standard deviation, is shown through Pareto's front. An index of merit based on area calculation under Pareto's front is defined and used for transmission line set comparison

A noninvasive methodology to evaluate and classify electrical system failures is presented in this work. It is based on the electrical system magnetic signature recognition by using the wavelet signal decomposition and the resulting variance spectrum evaluation, respectively. The proposed methodology was validated by comparing theoretical and experimental results. The finite-element method was used in the numerical simulations of the magnetic flux density, and a postprocessing approach was adopted in the signal decomposition and analyses. An experimental setup was built to obtain the magnetic signature regarding some preselected fault configurations.

O objetivo deste trabalho é apresentar uma metodologia de cálculo da distribuição de correntes e dos campos eletromagnéticos e tensões induzidas associadas em estruturas atingidas diretamente por descargas atmosféricas que, agregada à filosofia geral de compatibilidade eletromagnética (CEM), constitua uma abordagem inovadora e abrangente quando comparada às recomendações de proteção contra descargas atmosféricas atuais. Propõe-se, portanto, desenvolver uma metodologia que: · Constitua uma ferramenta de auxílio nas tomadas de decisões, aplicável desde a etapa de definição da arquitetura da estrutura e do leiaute dos equipamentos até a definição final da configuração do sistema de proteção contra descargas atmosféricas (S.P.C.D.A); · Possibilite a implementação de uma filosofia de proteção dos equipamentos e sistemas elétricos e eletrônicos contra descargas atmosféricas na qual se integre as recomendações tradicionais às necessidades atuais relacionadas à área de compatibilidade eletromagnética; · Seja abrangente e com grau de precisão satisfatório, quando comparadas com as recomendações atuais, com possibilidade de exploração dos valores das grandezas elétricas envolvidas no domínio do espaço e do tempo, e · Apresente simplicidade na implementação em computadores pessoais. The main purpose of this work is to present a suitable method for calculating the current distribution, the electric and magnetic field, and the induced voltage on electric circuits regarding a structure directly struck by lightning. Moreover, when the method is used together with the electromagnetic compatibility (EMC) requirements, it can provide the designer with a new and helpful methodology meeting the recent aspects or the state of the art on lightning protection systems (L.P.S). Thus, a methodology is proposed, which provides the L.P.S. design team with: · The availability to take technical decisions in all steps of the project, from the definition of the architecture of the structure to the definition of the best layout of L.P.S.; · Recommendations to achieve the EMC of the electric and electronic system, in addition to the traditional ones; · Reliable numerical results concerning simulations in the space and time-domain, and · Simple implementation in personal computers.

This paper was partially supported by CNPq (Brazil) under the Grant PQ 307867 2011-0; International audience; In EMC behavior of power electronic converters, it is important to predict near-field coupling between the complex components (e.g. in EMC filter). By using the components of near-field multipolar expansion of electromagnetic sources, the close magnetic coupling between two sources is determined from their equivalent model. It is shown that the complete identification of all components of multipolar expansion provides a more precise representation of the near-field around sources and thus a better accuracy of the near-field coupling prediction. Also theoretical and experimental developments are presented.

PurposeThis paper aims to present an evaluation of the crosstalk models developed for a shareware version of Spice.Design/methodology/approachThe transmission line model is compared with π lumped circuit models by varying the number of cells. The influence of losses is also introduced, and some constraints regarding the models are examined, showing the suitability of the new Spice libraries developed by the authors. In order to validate the theoretical results some experiments were carried out.FindingsThe paper finds that Spice is a powerful engineering tool for students and technicians involved in EMC analyses.Originality/valueThe main aspects concerning the accuracy and integrity of the experimental data are emphasized and discussed in this paper.

Brazil's electric power utilities have commonly employed native timbers as the main material for manufacturing cross-arms for distribution lines. However, the increasingly high costs of these timbers and Brazil's new environmental laws have contributed to change this situation, spurring research on new materials for application in transmission and distribution systems. This paper discusses two reforested wood species, Pinus elliottii and Eucalyptus citriodora, coated with castor oil-based polyurethane resins, as an alternative material for distribution line cross-arms, from the standpoint of their mechanical and electrical properties and their low cost. Numerical simulations and a complete description of the entire coating process are also part of this work.

Este trabalho apresenta uma metodologia para a determinação da densidade superficial de carga em duas estruturas simples, um fio reto finito e uma chapa plana quadrada ambas submetidas a um potencial constante. A metodologia envolve o método dos momentos, utilizando como função de expansão as wavelets de Haar ao invés da função pulso, visando a obtenção de uma boa precisão e de uma redução no esforço computacional. Através de um artifício matemático, podemos selecionar um limiar em porcentagem que permite descartar valores próximos de zero, sem grandes variações no resultado final. Apresentamos também as vantagens computacionais, que podemos obter através da decomposição de Cholesky.

This paper presents the mathematical basis, and some results, concerning the application of the Haar's Wavelets as the expansion function in the method of moments. Some computational optimization techniques are used, and their main aspects are stressed in the paper. As an example, the surface charge density on a finite and thin plane plate calculation is presented, in which the main computational performance aspects are evaluated.

Presents the mathematical basis and some results, concerning the application of Haar's wavelets, as an expansion function, in the method of moments to solve electrostatic problems. Two applications regarding the evaluation of linear and surface charge densities were carried out: the first one on a finite straight wire, and the second one on a thin square plate. Some optimization techniques were used, whose main computational performance aspects are emphasized. Presents comparative results related to the use of Haar's wavelets and the conventional expansion functions.

The effects resulting from direct lightning strikes to buildings may affect the reliable operation of electric and electronic systems installed inside. The influence of such phenomena on equipment and systems depends on the immunity levels, and on the magnetic field intensity due to the lightning current. In this paper, a time-domain simulation of the lightning induced voltage on electric circuits (open metal loops) located inside a high building, a steel structure, is presented. In order to make an extensive analysis, the simulation is carried out considering different regions within the building. The results related to magnetic flux density and induced effects, helpful in determining the critical positions of equipment, are presented, and some of them are compared with those obtained from other methodologies proposed in the literature.

Texte complet accessible : http://www.hindawi.com/journals/ijap/2012/102495/; International audience; The electromagnetic interference between electronic systems or between their components influences the overall performance. It is important thus to model these interferences in order to optimize the position of the components of an electronic system. In this paper, a methodology to construct the equivalent model of magnetic field sources is proposed. It is based on the multipole expansion, and it represents the radiated emission of generic structures in a spherical reference frame. Experimental results for different kinds of sources are presented illustrating our method.

ISBN: 978-85-64619-00-5 e-ISBN: 978-85-64619-04-3 Plein texte : http://omnipax.com.br/livros/2011/CEPE/CEPE-livro.pdf; The growing concern about the electronic equipment certi cation has fueled e orts to develop methodologies and test equipments for electromagnetic compatibility (EMC) analysis. Nowadays, reverberation chambers are the focus of research studies on the development of EMC test equipments. This article proposes a characterization and optimization procedure to analyze a reverberation chamber excited by transmission lines. We have used multi and mono-objective evolutionary computation (Genetic Algorithms) procedures in order to understand the chamber behavior and optimize it, respectively. Results are shown as a contribution to the analysis of reverberation chambers.

Texte complet disponible sur le site du journal ISSN 1516-7399 : http://www.jmoe.org/; International audience; This paper presents an evaluation of the phase shifting excitation and load effects in a Transmission Line Exciting Chamber. This chamber is suggested as an alternative for immunity tests because of the restrictions related to canonical chambers. Here, two methods are used to calculate the E-field: a semi-analytic approach and a numerical one. The semi-analytic method is based on the modal expansion while a software is used for numerical simulations. The results regarding the E-field profile and the related statistical indexes of merit are presented and used to evaluate the chamber performances. Experiments were also conducted in order to evaluate the chamber.

In wind electrical energy generating systems, due to fast voltage and current fluctuations, the power converter represents a source of electromagnetic disturbances. EMI problems of stand alone wind generators are here analysed in order to take into account many different power quality problems which result in voltage fluctuations and harmonics in the net. This paper, moreover, presents a wind turbine experimental simulator (WTES) that moves a wind electrical energy generating system (WEEGS) to carry out EMI measurements and the relative experimental results. The WEEGS here taken into account comprises a wound rotor induction generator (WRIG) in which the frequency transformation from the rotor to the stator windings generate interharmonics and the direct connection between stator and grid increase the sensitivity to voltage sag. These two aspects are here discussed and the existing solutions are pointed out.

International audience; This paper presents a procedure for evaluating the performance of reverberation chambers, by approximating the maximum working volume in a given configuration. The evaluation of this volume is based on the geometrical and physical constraints, e.g., the ones related to the internal E-field distribution recommended by standards. The importance of the present work is related to the development of a non-canonical reverberation chamber configuration, whose excitation is carried out by transmission lines, instead of antennas plus paddles.

This paper revisits the design of L and S band bridged loop-gap resonators (BLGRs) for electron paramagnetic resonance applications. A novel configuration is described and extensively characterized for resonance frequency and quality factor as a function of the geometrical parameters of the device. The obtained experimental results indicate higher values of the quality factor (Q) than previously reported in the literature, and the experimental analysis data should provide useful guidelines for BLGR design.