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The search for more competitive equipment in the global market has led to the implementation of new materials and technologies in the search for greater energy efficiency. This is certainly a guideline followed by the electric motor industry that has introduced new technologies in rotating machines, such as the permanent magnet motor, evolving into increasingly efficient motor classes. However, subjecting these efficient motors under nonideal electric grid power conditions, such as voltage unbalance, can cause these efficient machines to generate additional distortions in the voltage and current waveforms, which in turn not only affect the performance of electric motors themselves but also that of the electrical system in general. This work presents a comparison between energy efficiency gain and the corresponding power quality degradation through a detailed harmonic analysis of the effects of voltage harmonics and voltage unbalance in three 0.75-kW electric motors classes: IE2, IE3, and IE4, The results show that for increasing percentages of a specific harmonic distortion, other harmonics are also increased in the higher efficiency electric motors sample analyzed, and similar responses were also observed for large percentages of voltage unbalance, mainly in the line-start permanent magnet motor class IE4. The results achieved are interesting but rigorously reflect only the tested motor sample and cannot be generalized to all motors, in other power ranges, of the respective motor classes tested. For generalization, exhaustive tests must be accomplished to formulate general conclusions according to the electric motors’ classes commercially available.

Assessing the transient behavior of electric power transmission/distribution systems, when they are subjected to major disturbances such as lightning discharges, is an essential procedure to ensure the operational security of these systems, in order to supply good quality power to all consumers. Electromagnetic transient studies are routinely performed in the planning and operation phases of these systems, by using world widely known computer programs, among which stands out the Alternative Transient Program (ATP), via its graphical interface ATPDraw. However, preparing files for running case studies by using ATPDraw can become a time-consuming and human error-prone task. To overcome this drawback, this paper presents a toolbox for automatic generation and execution of Alternative Transient Program input files based on information directly obtained from technical databases of distribution utilities. This toolbox aims to reduce modeling time and susceptibility to human errors in the process of describing the grid in the software input file, which constitute the biggest obstacles to the extensive use of this program in real electric transmission/distribution networks. For the toolbox validation, a comparison was made between the input file generated by the ATPDraw auxiliary graphic interface and the file generated by the proposed toolbox by using the IEEE 13-bus and IEEE 34-bus test feeders. Besides that, the simulation results of both feeders for both softwares were compared, so that the correct operation of the Alternative Transient Program automatic case creator and executor proposed in this article were proved. In addition, the automatic generation of ATP cases for larger grids is exemplified with the IEEE 123-bus test feeder.

Este artigo apresenta uma análise da rede elétrica do campus Guamá da Universidade Federal do Pará com o objetivo de corrigir o baixo fator de potência que a universidade vem enfrentando desde 2017 e foi agravado pela pandemia de COVID-19. A contribuição deste trabalho é dimensionar um banco de capacitores para realizar a compensação de reativo no campus e consequentemente diminuir as multas referentes ao excedente de reativo.

In recent years, some research and development (R&D) companies in the energy area have been developed by the Federal University of Para (UFPA) within the University City Campus Professor Jose Silveira Netto. These projects have included elements of a Smart City on the Campus. However, there is still no survey to identify which indicators of a smart city are already present on the Campus and how smart it is. Therefore, this article will present the application of the Brazilian Standard ABNT NBR ISO 37122: 2020 of Smart Cities Indicators at the UFPA Headquarters Campus, with the objective of verifying which Smart City indicators are already present on the Campus due to the development of an electric mobility R&D. In addition to being the first time this standard has been applied on Campus, this work is also the first to carry out such a survey. As a result, a checklist was generated, where it was possible to count 4 categories and 17 indicators present within the Campus. Thus, demonstrating that UFPA is starting its process of insertion in the concept of Smart Cities.

The evolution of electric motors is increasing exponentially; it is currently possible to obtain efficiencies of around 96% with the IE4 efficiency class. A global interest in the transition to more efficient electric motors is being adopted in more countries through the Minimum Energy Performance Standards (MEPS), including Brazil, in which the minimum efficiency class level from August 2019 is the IE3 class, published in 2017 by Interministerial Ordinance No. 1. Considering the new energy scenario and aiming at new editions with greater efficiencies as minimum requirements, the present work presents a study of the voltage unbalance with under and overvoltage impacts on the performance of a Line Start Permanent Magnet Motor (LSPMM). The results show that the voltage unbalance with under voltages results in improvements in relation to the power factor, however voltage unbalance also results in increases in current harmonic distortion, therefore, this parameter must be analysed in systems with unbalance percentages greater than 1%.

A técnica de virtualização baseadas em contêineres vem sendo amplamente utilizada através da adoção de tecnologias como Docker e Kubernetes que permitem a criação e o gerenciamento de contêineres. Assim, o presente artigo utilizou o Prometheus e o Grafana para analisar a performance de um cluster Kubernetes executando a plataforma Dojot e recebendo dados de um simulador. Foi possível observar que o uso dos recursos de CPU e memória RAM são maiores nas máquinas Workers do cluster, onde quanto mais serviços da Dojot a máquina executa maior o consumo dos recursos. Concluiu-se que a utilização do Kubernetes juntamente com os seus recursos de gerenciamento e monitoramento são recomendáveis para aplicações que precisam se escaláveis.

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.

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.

A falta de alta impedância (FAI) é caracterizada pelo contato de um cabo energizado em alta ou média tensão em uma superfície de alta impedância, produzindo uma corrente insuficiente para sensibilizar os dispositivos de proteção deixando o sistema energizado, podendo causar vários danos e até mortes de animais e seres humanos. As experiências práticas que replicam a FAI são úteis para uma melhor compreensão de suas características, sendo a obtenção experimental destas uma tarefa árdua. Este trabalho apresenta considerações e resultados experimentais da análise complementar da viabilidade do uso de uma Fonte Ressonante (FR) em um laboratório de alta tensão, já proposta como ferramenta para estudos experimentais de FAI devido aos bons resultados inicialmente nela obtidos. Neste artigo são apresentados resultados conclusivos sobre a possibilidade de registro das oscilografias de FAI produzidas pela FR e da continuidade do uso desta nestes estudos.

Energy losses are a fundamental issue in the electricity distribution sector, being an inevitable consequence of transporting energy from supplying sources to consumers&rsquo, installations and are becoming one of the factors to be considered in planning and operation of electrical distribution networks. So, electrical distribution losses must be continuously monitored so that they are kept within acceptable levels to ensure the business profitability as well as the good power quality of supplied energy. In this context, this work introduces a modified methodology for technical losses calculation with the application of the concept of reduced equivalent networks, via definition of an Equivalent Operational Impedance, taking as a starting point the electrical network modeling in the Open Distribution System Simulator (OpenDSS). The losses calculation also considers customer&rsquo, s energy billing measurement data, measurements of injected energy and power factor at the feeder&rsquo, s coupling bus at the substation, also considering measurement campaigns to characterize the load consumption profiles for working days, Saturdays and Sundays. The proposed methodology disaggregates energy injections in billed energy, technical and non-technical losses parcels, and presents, as the results have demonstrated, a good precision in the proposed calculation procedures.

A baixa magnitude de corrente produzida por uma falta de alta impedância (FAI) é uma de suas principais caracterís-ticas, fazendo com que sua detecção e localização sejam dificultadas para os equipamentos utilizados atualmente na proteção dos sistemas elétricos de potência, ficando então o condutor energizado, agravando a possibilita de ocorrência de incêndios e o risco de mortes de seres vivos. Registros das características da FAI em árvores é uma lacuna na literatura, a qual dificulta ainda mais o desenvolvimento de novos algoritmos de detecção e métodos de localização. Este estudo apresenta detalhes das caracte-rísticas de tensões e correntes de FAI em galhos de árvore do tipo Ipê Roxo, resultado de testes experimentais realizados em la-boratório projetado e montado para simulação de FAI em redes aéreas de distribuição, visando à obtenção de dados para uma fu-tura modelagem de FAI shunts em árvores. A captura dessas oscilografias foi realizada por um relé de proteção comercial.

Esse artigo apresenta o projeto e a montagem de um laboratório para testes experimentais de faltas de alta impedância (FAI) em redes aéreas de distribuição. Testes experimentais de FAI em uma instalação elétrica trifásica de média tensão podem ser usados para determinar características e, por conseguinte, modelos matemáticos de FAI. O laboratório pode também ser usado para validação de métodos de detecção de FAI introduzidos como função em relés de proteção. O laboratório é composto essencialmente por um transformador trifásico de 225 kVA - 220 V/13,8 kV, um relé de proteção, uma contatora, disjuntores, elos fusíveis, cabos, TPs, TCs, um transformador trifásico de 75 kVA - 13,8 kV/220 V, cargas elétricas, e as diferentes superfícies de contato como objetos de teste. Nesse artigo, as principais características de FAIs foram levantadas, para diferentes superfícies de contato, por meio de testes experimentais realizados no Laboratório de Alta e Extra Alta Tensão (LEAT) da Universidade Federal do Pará (UFPA), em Belém-PA.

Between problems in the power grid expansions, distributed generation, energy market customers migrations, commercial losses and other problems, power distribution companies seek to improve both energy quality and costs reductions, enhancing profitability. A basic and crucial point for any energy company is how much energy to buy. That is, determining the amount of energy to be purchased as close as possible to that needed to serve its customers, avoiding financial losses by consuming more or less than they have. However, this is not a trivial problem, as energy consumption depends on several exogenous and endogenous factors, such as all the problems previously mentioned, in addition to economic, social, climatic, political and cultural aspects, among others. Thus, energy forecasts are realized with aid of both statistical analyzes and computational techniques. This article exposes a very short and short term energy forecast model using Neural Networks and feedback, applied in the new global context: the new coronavirus pandemic and its implications for energy consumption. The method was implemented with a real consumption dataset provided by the Brazilian energy company Equatorial from Para State and from Maranhao State. Very short term energy forecasts results reached a MAPE of around 1.2% in a 15-day window for both States, Para and Maranhao. For short term energy forecasts, results for both States were 3 possible scenarios in a window from June to December 2020, due to the unpredictability of the pandemic, especially in Brazil, which so far has shown no signs of reducing the contagion curve.

The measurement and analysis of partial discharges (PD) are like medical examinations, such as Electrocardiogram (ECG), in which there are preestablished criteria. However, each patient will present his particularities that will not necessarily imply his condemnation. The consolidated method for PD processing has high qualifications in the statistical analysis of insulation status of electric generators. However, although the IEEE 1434 standard has well-established standards, it will not always be simple to classify signals obtained in the measurement of the hydro generator coupler due to variations in the same type of PD incidence that may occur as a result of the uniqueness of each machine subject to staff evaluation. In order to streamline the machine diagnostic process, a tool is suggested in this article that will provide this signal classification feature. These measurements will be established in groups that represent each known form of partial discharge established by the literature. It was combined with supervised and unsupervised techniques to create a hybrid method that identified the patterns and classified the measurement signals, with a high degree of precision. This paper proposes the use of data-mining techniques based on clustering to group the characteristic patterns of PD in hydro generators, defined in standards. Then, random forest decision trees were trained to classify cases from new measurements. A comparative analysis was performed among eight clustering algorithms and random forest for choosing which is the superior combination to make a better classification of the equipment diagnosis. R2 was used for assessing the data trend.

The high impedance fault (HIF) has as one of its main characteristics the low magnitude of the current produced, causing its detection and location to be impaired for the equipment currently used to protect electrical power systems, which favors the driver remain energized, increasing the likelihood of fires and the risk of death for living beings. Records of HIF characteristics in trees are a gap in the literature, making it difficult to develop new algorithms and identification methods. This study presents details of the voltage and current characteristics of HIF in bamboo tree branches, the result of experimental tests carried out in a laboratory designed and assembled for HIF simulation in overhead distribution networks, and the capture of these oscillography was carried out by a relay commercial protection.

Este trabalho tem por objetivo analisar a influência da definição do fator de potência em estudos de fluxo de carga com o objetivo de realizar o cálculo de perdas técnicas ativas e reativas, utilizando um sistema teste simplificado e um sistema de distribuição real, pertencente à área de concessão da distribuidora do estado do Pará. Será apresentada a importância de se utilizar um fator de potência que melhor represente a característica da carga da área de concessão e um algoritmo que configure o fator de potência das cargas de acordo com os dados de medição em alimentadores ou transformadores de distribuição. Os resultados mostraram as diferenças no cálculo de perdas técnicas quando da utilização do fator de potência regulatório e o fator de potência real verificado nas cargas.

O presente trabalho utiliza o software OpenDSS para modelar uma rede elétrica de distribuição, capaz de simular o comportamento da rede elétrica e os impactos na qualidade de energia elétrica de acordo com as diferentes topologias de transformadores, cargas e fontes de geração distribuída em que uma rede elétrica pode ser submetida. Como estudo de caso, o artigo utiliza dados reais da rede da Universidade Federal do Pará e a inserção de geradores solar fotovoltaicos em diferentes pontos da rede, como demonstração do impacto na redução da potência ativa, na elevação do nível de tensão e na redução de perdas elétricas de acordo com a inserção da geração distribuída (GD) na rede elétrica estudada.

Este artigo tem como objetivo apresentar os benefícios da metodologia de manutenção centrada em confiabilidade para determinação de tarefas otimizadas de manutenção aplicadas a um item do acionamento elétrico de um moinho SAG de uma indústria mineradora. Será apresentada a importância da manutenção para os equipamentos e quanto a utilização de técnicas modernas auxilia as grandes corporações a atingir maior lucratividade e competitividade no mercado atual.

A principal característica de uma falta de alta impedância (FAI), falha recorrente em redes aéreas de distribuição, é a baixa magnitude de corrente produzida, o que torna difícil sua detecção e localização pelos equipamentos comumente utilizados para proteção, ficando o condutor energizado, o que possibilita a ocorrência de incêndios e o risco de mortes. Registros das características da FAI em árvores é uma lacuna na literatura, a qual dificulta o desenvolvimento de algoritmos e métodos que possam facilitar sua detecção e localização. Este estudo apresenta detalhes das características de tensões e correntes de FAI em galhos de árvore do tipo Castanhola, resultado de testes experimentais realizados em laboratório projetado e montado para simulação de FAI em redes aéreas de distribuição, tendo sido a captura dessas oscilografias realizada por um relé de proteção comercial.

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.

This article presents a comparison of using techniques of optimal load flow and decision tree in making corrective voltage control actions for electrical power systems under insecure operation condition, that is, with voltage constraints violated. The decision tree technique is used in conjunction with a technique of sensitivity analysis in such a way that control actions are taken to be more effective to eliminate the voltage constraints violation in each case of contingency analyzed. A comparison is made between the control actions suggested by the optimal load flow strategy and those suggested by the decision tree for the same operating condition, discussing the achievement of implementing these actions in a real power system. The analysis methodology proposed here is tested in a real power system of a Brazilian utility, which operates in the State of Amapa - Brazil. The results showed how both methodologies can be used as operational tools in power system supervision and control centers.

The objective of this paper is to investigate the behavior of electromagnetic forces during the occurrence of faults inside transformers as result of transients in the electrical systems. The methodology is based on the modeling of a single-phase 50-MVA transformer subjected to inrush currents through finite-element method. In this perspective, the values of inrush currents, obtained by the alternative transient program software, are used to estimate the magnetic field density dispersion in the transformer, and to find the values of forces in axial and radial directions. These forces components are distributed along the energized windings for observing the loads behavior in high-voltage windings. This paper will thus present investigations of electromagnetic forces, structural deformation, stresses, and safety factor on transformer's winding when subjected to inrush current.

Atualmente, são utilizados diversos processos para a geração de energia elétrica, como por exemplo: usinas hidrelétricas, termoelétricas, nucleares, eólicas, solares, entre outras. Também, neste atual cenário, podem-se ressaltar as usinas virtuais, pois estas são responsáveis por disponibilizar energia por meio de ações de eficiência energética. Portanto, este artigo apresenta o direcionamento a esta forma de geração de energia, a qual fica disponibilizada, por alguma ação de eficiência energética, para outro uso na sociedade. A usina virtual apresentada neste trabalho é baseada em pesquisas de ações de eficiências no sistema nacional de iluminação pública por meio do uso de lâmpadas com maior índice de eficiência e maior vida útil, o que permite a disponibilidade de energia a outros setores, reduzindo gastos quanto a investimentos e melhorando os níveis de tensões do sistema elétrico. Com isso, pode-se considerar como uma usina geradora de energia.

Photovoltaic systems can strengthen the energy matrix aiming at energy sustainability, however, their intermittence, the availability time frame and seasonality effects are complicating aspects for the operation of these systems. To mitigate such problems, a possible measure is the operation of hybrid systems (HS) associated with storage systems to meet the energy demand. This study presents real operational scenarios for the management of a hybrid mini-grid installed in the Amazon region in Brazil, capable of managing energy supply and demand, changing the generation curve, reducing fossil fuel consumption and energy costs, in addition to providing flexibility and operational safety to the electrical operating under on-grid or off-grid conditions. Through technical and economic analyses, the objective of this study is to show that hybrid systems can be implemented in small and medium consumers, in addition to generating a new market option for utilities. This research evaluates the operation of HS concurrently with the electrical grid and the results show that the system meets the technical requirements, in addition to bringing financial and ecological benefits. This information can support the decisions of consumers, utilities and energy operators for the development of the national market for on-grid and off-grid HS.

This paper proposes a new methodology based on the use of Resonance Index (RI) analysis as a posteriori decision-making procedure to check solutions of the optimization algorithm NSGA-II against resonance, when applied to the capacitor banks placement problem in radial distribution systems. Most of existing methodologies approach harmonic resonance in the referred problem through the inclusion of constraints in the optimization procedure with respect to the harmonic distortion indexes THD and IHD. However, monitoring only these two parameters is not sufficient to identify specific problems on capacitor banks due to harmonic resonance. To demonstrate this point, a RI analysis using the resonant chart was performed considering a 34-bus radial system. Also, the proposed a posteriori analysis is compared with the one that includes directly RI as a constraint in the optimization procedure, demonstrating that the proposed approach has a better performance with respect to computational time.