Adroaldo Raizer - Academia.edu (original) (raw)

Papers by Adroaldo Raizer

Energies, Jan 8, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Revista Tecnologia & Humanismo, 1998

International Symposium on Electromagnetic Compatibility, 1998

Based on regulatory guidance regarding the prevention of electromagnetic (EM) problems, we evalua... more Based on regulatory guidance regarding the prevention of electromagnetic (EM) problems, we evaluate the EM interference of an axially ruptured coaxial cable used in a nuclear power plant. We investigate regulatory guidance on EM interference and susceptibility (EMI/EMS) to safely operate a nuclear power plant. We analyze the ruptured coaxial cable rigorously using a modematching method in an electrostatic domain, based on Laplace's equation and the superposition principle. We perform potential formulation, enforcement of boundary conditions, and examination of the convergence of the resulting series solution. We then extract the distributions of the potential and electric field and the normalized capacitance while the geometric and material parameters of the axially ruptured coaxial cable change. Consequently, we evaluate the EMI of the axially ruptured coaxial cable by interpreting the derived results. We conclude that the evaluation results provide us with the insightful information to mitigate EMI-related problems.

Progress in Electromagnetics Research Letters, 2010

The straightforward comparison between electromagnetic environment measurements and immunity leve... more The straightforward comparison between electromagnetic environment measurements and immunity levels for industrial, scientific, and medical equipment has been used in the technical literature as an ordinary method to provide electromagnetic compatibility management within critical areas, such as hospital and industrial environments. This paper addresses a theoretical discussion concerning emission and immunity test features to focus the aforementioned problem. Finally, a more reliable comparison method is proposed, the environmental compatibility level definition, using analytical analysis and measurement results.

HAL (Le Centre pour la Communication Scientifique Directe), Jul 1, 2011

LGEP 2011 ID = 873International audienc

Compel-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering, Sep 1, 2003

This paper presents the use of transmission-line modelling-time domain (TLM-TD) method to analyse... more This paper presents the use of transmission-line modelling-time domain (TLM-TD) method to analyse the fields in mode stirred reverberation chambers excited by wires. It will be shown how the fields inside the chamber are distributed for a large range of excited frequencies. The work intends to develop a numerical procedure to verify the effectiveness and usefulness of the TLM method to electromagnetic compatibility problems. The numerical model presented here is based on the classical symmetrical condensed 3D node. The simulations will be compared with method of moments results obtained in available benchmark data. Some comments are made on comparisons between the two techniques.

ABSTRACT Validating measurements of electromagnetic field in near-field zone is a general target ... more ABSTRACT Validating measurements of electromagnetic field in near-field zone is a general target in research within electromagnetism area. This paper aims to present the results obtained from measurements and simulations of near-fields generated by a stand-alone electronic device. Measurements were performed in an anechoic chamber using probes connected by optical fibers as well as simulations using commercial software and own codes based on TLM-TD method.

Springer eBooks, 2003

In this paper we present efficient models to study the coupling of an electromagnetic wave with e... more In this paper we present efficient models to study the coupling of an electromagnetic wave with electronic equipment enclosures. The 3D Maxwell’s equations are solved using a Finite Element Time Domain method (FETD) and Transmission-Line Modeling Method (TLM). Numerical results are compared with those obtained by measurements or already published results.

IEEE Transactions on Electromagnetic Compatibility, Aug 1, 2016

This paper promotes the use of prediction methods as an alternative tool for evaluating and manag... more This paper promotes the use of prediction methods as an alternative tool for evaluating and managing electromagnetic compatibility (EMC) in hospital environments. Radiated emissions originated from medical equipment are modeled based on open area test site measurements, and they are applied to numerical simulation using transmission line matrix method (TLM). TLM simulation is performed to include not only the multipath effects provided by obstacles, but also the interaction and coupling of all different sources/models operating simultaneously on the environment under test (a typical operating room). This approach provides a useful tool in order to assess electromagnetic profiles established within the room area, and it allows implementing optimization processes such as genetic algorithms (GA). GA is employed to evaluate many different placements of medical equipment within the environment under test. A fitness function is defined to minimize the average electric field inside the room, providing a better equipment disposal to develop a preliminary EMC management program..

Iet Microwaves Antennas & Propagation, 2011

This study proposes a deterministic tool based on the combination of the transmission line modell... more This study proposes a deterministic tool based on the combination of the transmission line modelling method and a Kriging interpolation to search for optimal transmitter locations in indoor wireless systems. As a first step, the relevance of the technique is presented. Secondly, the methods are described based on their own formulations. Following, the methodology to combine the methods is presented where a simple case is used to exemplify the procedure and evaluate the accuracy. A two-dimensional (2D) complex case is presented to verify the robustness of the technique, and a 3D environment is studied to demonstrate the tool capability.

ABSTRACT In order to assist in the location of EHV transmission line faults using travelling wave... more ABSTRACT In order to assist in the location of EHV transmission line faults using travelling wave transients a program has been devised where the transients are simulated and compared with those recorded. The simulation scheme is based on the well-known ATP program, which has been found to be satisfactory for sample step times of 800 ns. The fault transients have been recorded at a 800 ns sample rate via a current probe attached to the secondary circuit of the current transformers. An offline analysis program has been written in Matlab™ which then converts the simulated transients into a form that allows direct comparison with the recorded transients and also provides extra analysis routines. This greatly improves the confidence in a given fault location estimate. Example faults recorded on the ScottishPower EHV transmission system are given which demonstrate the utility of this scheme.

IEEE Transactions on Magnetics, Mar 1, 1992

When applying the finite element method in electromagnetic field determination of high frequency ... more When applying the finite element method in electromagnetic field determination of high frequency magnetodynamic phenomena a serious obstacle is encountered: the discretisation of the areas where the skin effect is very strong. The experience already acquired in handling this type of problem shows that the accuracy of the solution depends on many factors such as the order of the elements used and the length of the elements. The immediate conclusion is that a classical finite element solution is very expensive in terms of computer memory and central processing unit time. So techniques minimising the computing cost are sought, such as the impedance boundary condition, which will be extended here for axisymmetric problems.

IEEE Transactions on Magnetics, Jul 1, 2000

This paper presents the application of two numerical methods in the analysis of the coupling of a... more This paper presents the application of two numerical methods in the analysis of the coupling of an incident wave with a conducting wire inside a metallic cavity having a small aperture. The Finite Element Method in the frequency domain and the Transmission-line Modeling Method are the numerical methods used in the analysis. Earlier published experimental results are used in order to evaluate the obtained numerical results.

It is not uncommon to study motors using two-dimensional Finite Element Method (FEM) models, or i... more It is not uncommon to study motors using two-dimensional Finite Element Method (FEM) models, or in symmetry cuts represented of the complete model. These assumptions can still present consistent results and a considerable computational advantage for the design of machines and other assessments under normal operating conditions. However, it can be observed that FEM is still hardly used in modeling and diagnosis of motors failures, even with coherent and promising results. In some failure situations, it can be highlighted that some typical geometric conditions of simplification may cease to exist, which makes the 3-D models more comprehensive and representative under these circumstances. Thus, the present work aims to contribute to development of fault diagnosis field in induction motors, pointing out the possibility of implementing three-dimensional FEM models to simulate faulty motors. Furthermore, it intends to demonstrate that, although complex and almost underexplored, faulty motors 3-D modeling is viable, promising and has significant advantages over 2-D.

Studies indicate that approximately 100 million lightning flashes reach Brazilian soil per year, ... more Studies indicate that approximately 100 million lightning flashes reach Brazilian soil per year, causing damages to both energy utilities and consumers. In critical periods, with great atmospheric activity, there is a significant increase in consumer complaints, due to high interruption rates and frequent fails in electrical equipment and installations. For that, data from previous researches, recent bibliographic sources, Brazilian standards and technical specifications of electric companies were used, in order to develop models that are as representative as possible in simulations in the ATPDraw. More than 1000 simulations were run out, resulting a data collection that allowed the elaboration of charts of occurrence cumulative probability of maximum overvoltages in the low voltage installations, due to direct lightning flashes in the medium and low voltage lines, in several types of lines and soil resistivity conditions. Analysis of these charts shows that the probability of high levels of overvoltage occurring at LV consumer electrical installations is low and, in the vast majority of cases, equipment malfunctions can be avoided with the proper use of surge suppression devices.

This paper concerns theory and implementation of p and h-p adaptive versions of finite element me... more This paper concerns theory and implementation of p and h-p adaptive versions of finite element method. The different procedures of adaptivity and the optimal mesh concept are discussed and a methodology to obtain optimal or quasi optimal meshes with hierarchical elements is presented. The error estimator used and the algorithm implemented are also presented. The efficiency is demonstrated in two classical 2D examples. In this examples, we have analysed both cases the regular solution and non regular one, and the meshes obtained during the adaptive processes are compared.

This paper presents the analysis results of field measurements of ground resistance and impulse i... more This paper presents the analysis results of field measurements of ground resistance and impulse impedance. First, the Current Derivative Method is presented, whose objective is to obtain the RLF steady-state ground resistance value from the transient impedance curve Z(t)Z(t)Z(t). Second, it is presented a study about the application of ground resistance measurement methods, for electrodes positioned at reduced distances, in impedance measurements under the same conditions, and it is concluded that these methods do not present satisfactory results. Based on the results, a proposal is presented for the development of a method with orthogonally positioned electrodes that allows field measurements without significant errors, both for ground resistance and for impulse impedance.

EDITORA CRV eBooks, Jun 16, 2021

ABSTRACT This work deals with a comparative study between two different techniques (Kriging and G... more ABSTRACT This work deals with a comparative study between two different techniques (Kriging and Genetic Algorithms) for optimal transmitter location in an indoor environment. Both techniques were applied for the same test function which is computed from the fields scattered in the environment. The Transmission Line Modeling Method Â¿ TLM was used for the objective function evaluations. For the tests, tow different environments were simulated, with different constitutive materials and geometries. Both methods were applied to search the position where the transmitter should be placed to provide the best electromagnetic environment illumination. From the simulations, it was possible to identify the weakness and the strengths for each method in each application. It was also possible to make an investigation of a telecommunication auto-planning tool based on numerical methods.