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Paulino J.O.S.,Federal University of Minas Gerais | Barbosa C.F.,Brazilian Center for Research and Development in Telecommunications | Lopes I.J.S.,Federal University of Minas Gerais | Boaventura W.D.C.,Federal University of Minas Gerais
IEEE Transactions on Power Delivery | Year: 2011

This paper presents an approximate formula for the peak value of lightning-induced voltages in an overhead line, considering the ground resistivity and a trapezoidal lightning return stroke current waveform with typical parameters 3.8-μ s front time and 120-m/μ s velocity. It presents an improvement in a formula previously proposed by the authors. The formula is used with a probabilistic approach, and the results are compared with theoretical and experimental results available in the literature. The results show that the proposed formula, although very simple, is in good agreement with results obtained using complete formulations and experimental data. © 2011 IEEE. Source


Paulino J.O.S.,Federal University of Minas Gerais | Barbosa C.F.,Brazilian Center for Research and Development in Telecommunications | Lopes I.J.S.,Federal University of Minas Gerais | Boaventura W.D.C.,Federal University of Minas Gerais
IEEE Transactions on Power Delivery | Year: 2010

An approximate formula is proposed to estimate the peak value of lightning induced voltages in an infinite line, considering the soil resistivity. The formula is derived from results of a computer code for lightning induced voltage calculation. The code is based on Rusck's formulation for the vertical electric field, for a perfect conducting earth, and the formulation for the horizontal electric field for finitely conducting earth proposed by Barbosa and Paulino. The electromagnetic field coupling with the line is carried out using the model proposed by Agrawal. The results are compared with experimental data from Barker for validation purposes. The paper also presents an extension of the methodology proposed in IEEE Std.1410 Guide to include the effect of the soil finite conductivity in the assessment of the lightning performance of distribution lines due to nearby strikes. The annual indirect lightning induced voltage flashover rates obtained with IEEE Std. 1410 method are compared with the approximate formula results. © 2010 IEEE. Source


Barbosa C.F.,Brazilian Center for Research and Development in Telecommunications | Paulino J.O.S.,Federal University of Minas Gerais | Boaventura W.D.C.,Federal University of Minas Gerais
IEEE Transactions on Electromagnetic Compatibility | Year: 2013

This paper presents a time-domain method for the calculation of the horizontal electric field at the earth surface due to lightning, when the earth structure is made up of two parallel horizontal layers of finitely conducting earth. The method is based on the assessment of the electric field at the surface considering the earth as homogeneous and with the electrical parameters of the first layer. The contribution of the second layer is considered by computing the waves reflected from the boundary between the layers, after they have propagated through the first layer. The paper also shows that the displacement currents could be neglected during the wave reflection, which leads to a simple expression for the reflection coefficient. The results from the method presented in this paper agree with results calculated using a known frequency-domain expression. © 1964-2012 IEEE. Source


Barbosa C.F.,Brazilian Center for Research and Development in Telecommunications
Proceedings of the 3rd International Conference on Applied Robotics for the Power Industry, CARPI 2014 | Year: 2015

This paper describes an eddy current sensor carried by a corrosion detection robot that operates on energized power lines. The robot is installed on a live overhead conductor and it is controlled by the ground-based operator using a portable computer and a radio link. The sensor carried by the robot is capable of detecting the remaining thickness of the zinc layer over the steel wires that make the core of the aluminum conductor steel reinforced (ACSR) commonly used in power lines. The sensor is made of a contactless coil that encircles the conductor and applies an alternating longitudinal magnetic field along the conductor. This field induces eddy currents in the zinc layer that changes the coil impedance, which is used to obtain the zinc layer thickness. The main sensor characteristics are described in this paper, such as its immunity to the load current, its enhanced sensibility due to a hybrid circuit, and its contactless coils that facilitates the sensor installation on the power line conductor. © 2014 IEEE. Source


Carrillo D.,Brazilian Center for Research and Development in Telecommunications
2015 IEEE Colombian Conference on Communications and Computing, COLCOM 2015 - Conference Proceedings | Year: 2015

The demand of radio-electric spectrum in cities with high density of users is growing every day. There are many initiatives that aim to meet this demand, one of these initiatives is to insert into wireless communication devices algorithms that alternate their band operation through technology called cognitive radios to allow users to maintain connectivity and transfer data securely in unlicensed bands. Often the study and evaluation of research trying to explore the capabilities of cognitive radios require much financial investment in cases in which the intention is to implement a real experimental network or to perform simulations using proprietary software. Thus, this article presents a case of using modules that are implemented within the framework of network simulator textit 3 (ns-3). The results of this simulation were validated with experimental results of a real cognitive network, which was implemented on CPqD campus in Campinas, Brazil. This simulator creates a variety of opportunities to assess cognition algorithms using an open source tool. The validation of simulations with ns-3 show consistency of results with those which were obtained in cognitive experimental network, thus cognitive radio simulator implemented in ns-3 can be used to evaluate algorithms considering a variety of scenarios without increasing costs. © 2015 IEEE. Source

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