Artigos em Revistas

Metodologias com abordagens diferenciadas que auxiliem o ensino e a aprendizagem em sala de aula têm sido muito estudadas, como a utilização da robótica educacional, laboratórios virtuais e dispositivos físicos que são ferramentas educacionais que atualmente estão se destacando quando se trata de novas propostas metodológicas para o ensino de Ciências e Matemática. Este trabalho investigou a utilização de um recurso para fins educativos por meio da plataforma BBC Micro:bit, como forma de engajar, motivar e promover o letramento computacional e científico dos estudantes dentro de uma cultura maker. A Aprendizagem Baseada em Projeto (PBL) e a interdisciplinaridade de forma integrada pelas disciplinas de Ciências, Tecnologias, Engenharia, Artes e Matemática (STEAM), por meio da metodologia STEAM, foram utilizadas nesta pesquisa. Foi elaborada uma oficina com o uso do Micro:bit, aplicada aos estudantes do primeiro ano do curso técnico em Informática, modalidade ensino médio regular da EETEPA Dr. Celso Malcher. Observou-se a partir dos resultados analisados o Micro:bit pode ser utilizado como ferramenta metodológica para ensinar os conteúdos vistos em sala de aula, principalmente quando utiliza-se a PBL e a metodologia STEAM de forma integrada.

MÁRCIA CRISTINA PALHETA ALBUQUERQUE, WELLINGTON DA SILVA FONSECA, DAVID GENTIL DE OLIVEIRA, RAFAEL DE CASTRO SOUSA

Direct lightning discharges in overhead distribution networks invariably cause serious insulation damage, frequently leading to the electric system’s partial or total shutdown. Installing lightning arresters can be very effective, and it is commonly used to minimize this problem; however, considering that typically, electric distribution grids exhibit a very large number of electrical nodes, the massive use of lightning arresters may not be economically viable. In this way, this article proposes a methodology for allocating lightning arresters that can significantly reduce the number of lightning arresters installed, but at the same time maintaining an adequate protection level for the distribution grid. The proposed methodology, named Direct Discharge Crossing (DDC), analyzes the network criticality based on two main factors, which are the overvoltage magnitudes and the number of flashovers provoked by lightning discharges, and defines a feeder lightning performance function that is used to indicate the recommended location for lightning arresters’ installation. The simulation studies are accomplished using the IEEE 34 bus distribution grid and ATP software to demonstrate the efficacy of the proposed solution, which is confirmed by the results presented.

RAPHAEL PABLO DE SOUZA BARRADAS, GABRIEL VIANNA SOARES ROCHA, JOÃO RODRIGO SILVA MUNIZ, UBIRATAN HOLANDA BEZERRA, MARCUS VINÍCIUS ALVES NUNES, JUCILENO SILVA E SILVA

Currently, for analyzing harmonic impacts on voltage at a point of interest, due to multiple nonlinear loads, the literature recommends carrying out simultaneous and synchronized measurement campaigns in all suspicious points with the use of high cost energy quality analyzers that are usually not available at the customers’ facilities and very often also not at the electric utilities. To overcome this drawback this paper proposes a method of assessing the harmonic impact due to multiple nonlinear loads on the total voltage harmonic distortion using only the load current true RMS values which are already available in all customers’ installations. The proposed methodology is based on Regression Tree technique using the Permutation Importance indicator which is validated in two case studies using two different electrical systems. The first case study is to ratify the use of Permutation Importance to measure the impact factor of each nonlinear load in a controlled scenario, the IEEE-13 bus test system, using ATP simulation (Alternative Transient Program). The second is to apply the methodology to a real system, an Advanced Measurement Infrastructure System (AMI) implanted on a campus of a Brazilian University, using low cost meters with only true RMS current measurements. The results achieved demonstrated the feasibility of applying the proposed methodology in real electric systems without the need for additional investments in high-cost energy quality analyzers.

FLÁVIA P. MONTEIRO, SUZANE A. MONTEIRO, MARIA E. TOSTES MARIA E. TOSTES, UBIRATAN H. BEZERRA

The efficient protection of electric power distribution networks against lightning discharges is a crucial problem for distribution electric utilities. To solve this problem, the great challenge is to find a solution for the installation of surge arresters at specific points in the electrical grid and in a sufficient quantity that can ensure an adequate level of equipment protection and be within the utility’s budget. As a solution to this problem of using ATP (Alternative Transient Program), this paper presents a methodology for optimized surge arrester allocation based on genetic algorithm (GA), with a fitness function that maximizes the number of protected equipment according to the financial availability for investment in surge arresters. As ATP may demand too much processing time when running large distribution grids, an innovative procedure is implemented to obtain an overvoltage severity description of the grid and select only the most critical electric nodes for the incidence of lightning discharges, in the GA allocation procedure. The results obtained for the IEEE-123 bus electric feeder indicate a great reduction of flashover occurrence, thus increasing the equipment protection level

GABRIEL VIANNA SOARES ROCHA, RAPHAEL PABLO DE SOUZA BARRADAS, JOÃO RODRIGO SILVA MUNIZ, UBIRATAN HOLANDA BEZERRA, IGOR MEIRELES DE ARAÚJO, DANIEL DE SOUZA AVELAR DA COSTA, ABNER CARDOSO DA SILVA, MARCUS VINÍCIUS ALVES NUNES, JUCILENO SILVA E SILVA

The efficient protection of electric power distribution networks against lightning discharges is a crucial problem for distribution electric utilities. To solve this problem, the great challenge is to find a solution for the installation of surge arresters at specific points in the electrical grid and in a sufficient quantity that can ensure an adequate level of equipment protection and be within the utility’s budget. As a solution to this problem of using ATP (Alternative Transient Program), this paper presents a methodology for optimized surge arrester allocation based on genetic algorithm (GA), with a fitness function that maximizes the number of protected equipment according to the financial availability for investment in surge arresters. As ATP may demand too much processing time when running large distribution grids, an innovative procedure is implemented to obtain an overvoltage severity description of the grid and select only the most critical electric nodes for the incidence of lightning discharges, in the GA allocation procedure. The results obtained for the IEEE-123 bus electric feeder indicate a great reduction of flashover occurrence, thus increasing the equipment protection level.

GABRIEL VIANNA SOARES ROCHA, RAPHAEL PABLO DE SOUZA BARRADAS, JOÃO RODRIGO SILVA MUNIZ, UBIRATAN HOLANDA BEZERRA, IGOR MEIRELES DE ARAÚJO, DANIEL DE SOUZA AVELAR DA COSTA, ABNER CARDOSO DA SILVA, MARCUS VINÍCIUS ALVES NUNES, JUCILENO SILVA E SILVA

Computer Numerical Control (CNC) is a technology made up of several blocks. Among these, lies the Trajectory Planning block, responsible for reference profile generation that are fed to position control loops. The need for Trajectory Planning arises from the mechanical constraints inherent to every plant to which CNC technology is applied. The machine’s operational limits myst be respected, in order to avoid several issues, such as: loss of precision, early wear of machine’s parts and excessive vibration. This paper proposes a novel smooth real-time trajectory generation setup based on an embedded system platform. A real-time snap and jerk bounded control algorithm is proposed, to achieve continuous and smooth feed motion in traditional Numeric Control code file, dealing both with straight lines and arcs. A local motion blending algorithm, applicable to the proposed method, is also presented. The developed algorithm was deployed to a BeagleBone Black, an embedded System-on-Chip, single board computer and tested in a prototype router machine. A comparison between the proposed method against the seven segments and trapezoidal acceleration methods is presented, both in terms of performance and of real-time computing viability. Simulation and Experimental results demonstrate the effectiveness of the proposed method to generate velocity, acceleration, jerk and snap bounded three dimensional trajectories, reducing the RMS error in up to 8.2% and 22.38% when compared to the Seven Segments and to Trapezoidal Acceleration methods, respectively. Assessing the error area on straight angles, the proposed method produced error areas 24% and 80% smaller when compared to the Seven Segments and to Trapezoidal Acceleration methods, respectively.

PAULO AUGUSTO SHERRING DA ROCHA, WERBESTON DOUGLAS DE OLIVEIRA, MARIA EMÍLIA DE LIMA TOSTES

This study presents a method to place, size, coordinate and adequate protection systems in distribution networks (DNs) with directly-coupled distributed generation (DG). DG penetration increase in DNs is beneficial to the operation of these grids. However, since the majority of DN is already consolidated, with protective devices sized for certain current levels and directionality, adding DG to these systems may cause issues. This study introduces a method to determine protective devices placement, their coordination and sizing, depending on DG location. Direct-coupled DG is considered since DG connected to DNs through power electronics limit the fault current to the network. Firstly, recloser allocation is treated in a multiobjective approach, reducing reliability indices. To solve this problem, particle swarm optimization is applied. Fuse cutouts allocation is determined by a set of rules, developed considering feeder particularities. After, DG is considered and its effects on the protection coordination are evaluated. To adapt DN to receive DG, fault current limiters are placed to avoid recloser – fuse miscoordination. Finally, recloser operation is analyzed to determine the operational philosophy to avoid misoperation in the presence of DG. Graphical and numerical results are presented for test systems to show the functionality and performance of the proposed method.

FERNANDO GUILHERME KAEHLER GUARDA, GHENDY CARDOSO JR., UBIRATAN HOLANDA BEZERRA, JOAO PAULO ABREU VIEIRA

This paper proposes the development of a three-phase state estimation algorithm, which ensures complete observability for the electric network and a low investment cost for application in typical electric power distribution systems, which usually exhibit low levels of supervision facilities and measurement redundancy. Using the customers´ energy bills to calculate average demands, a three-phase load flow algorithm is run to generate pseudo-measurements of voltage magnitudes, active and reactive power injections, as well as current injections which are used to ensure the electrical network is full-observable, even with measurements available at only one point, the substation-feeder coupling point. The estimation process begins with a load flow solution for the customers´ average demand and uses an adjustment mechanism to track the real-time operating state to calculate the pseudo-measurements successively. Besides estimating the real-time operation state the proposed methodology also generates nontechnical losses estimation for each operation state. The effectiveness of the state estimation procedure is demonstrated by simulation results obtained for the IEEE 13-bus test network and for a real urban feeder.

THIAGO MOTA SOARES, UBIRATAN HOLANDA BEZERRA, MARIA EMÍLIA DE LIMA TOSTES

This study presents an approach to calculate average technical losses (TLoss) and non-technical losses (NTLoss) in distribution grids using an equivalent operational impedance (EOI) calculated from a load flow solution for the transformers’ average loads, obtained from customers’ electric bills. If transformers are supervised, i.e. have available active and reactive power injections measurements or estimates from a state estimator program, the transformers’ average technical and non-technical losses can be calculated by running a load flow for the grid supplied by the transformer and using the definition of EOI presented in this study. For unsupervised transformers, i.e. no measurements or estimates are available, pseudo measurements of average active and reactive power injections can be obtained by a procedure that uses active and reactive power measurements at the feeder substation. The use of this methodology by electric utilities allows the calculation of technical and non-technical losses more accurately, as well as the inclusion of non-technical losses in the distribution networks operation planning. Results using the IEEE 13-bus test system and an urban real distribution grid are presented to demonstrate the effectiveness of the proposed methodology.

ALLAN R.A. MANITO, ALLAN R.A. MANITO, UBIRATAN H. BEZERRA,, THIAGO M. SOARES, JOÃO P.A. VIEIRA, MARCUS V.A. NUNES, MARIA E.L. TOSTES, RAFAEL C. DE OLIVEIRA

Computer Numerical Control is a technology made up of several blocks. The single most important of these blocks is the Control Unit, responsible for performing security checks, user interface, coordinating the motion, file handling and coordinating several peripherals usually used on CNC applications. Over the course of last years, embedded systems presented a huge improvement in processing power as well as easiness of use and application, given the advances in the open source and open hardware development community. The present paper presents the development process of a high-end embedded system based CNC controller, capable of operating including motion constraints up to the fourth order time derivative of position for each of the individual Cartesian axis.

PAULO ROCHA, EMÍLIA TOSTES