Navegando por Assunto "Qualidade de energia elétrica"

Agora exibindo 1 - 14 de 14

Acesso aberto (Open Access)
Análise de desempenho de algoritmos para classificação de sequências representando faltas do tipo curto-circuito em linhas de transmissão de energia elétrica
(Universidade Federal do Pará, 2019-12-05) FREIRE, Jean Carlos Arouche; MORAIS, Jefferson Magalhães de; http://lattes.cnpq.br/5219735119295290; CASTRO, Adriana Rosa Garcez; http://lattes.cnpq.br/5273686389382860
Maintaining power quality in electrical power systems depends on addressing the major disturbances that may arise in their generation, transmission and distribution. Within this context, many studies have been developed aiming to detect and classify short circuit faults in electrical systems through the analysis of the electrical signal behavior. Transmission line fault classification systems can be divided into two types: online and post fault classification systems. In the post-missing scenario the signal sequences to be evaluated for classification have variable length (duration). In sequence classification it is possible to use conventional classifiers such as Artificial Neural Networks, Support Vector Machine, K-nearest neighboors and Random forest. In these cases, the classification process usually requires a sequence preprocessing or a front end stage that converts the raw data into sensitive parameters to feed the classifier, which may increase the computational cost of the classification system. An alternative to this problem is the FBSC-FrameBased-Sequence Classification (FBSC) architecture. The problem with FBSC architecture is that it has many degrees of freedom in designing the model (front end plus classifier) and it should be evaluated using a complete dataset and rigorous methodology to avoid biased conclusions. Considering the importance of using efficient short-circuit fault classification methodologies and mainly with low computational cost, this paper presents the results of the KNN-DTW (K-Nearest Neighbor) algorithm analysis study associated with Dynamic similarity measurement. Time Warping (DTW) and HMM (Hidden Markov Model) algorithm for fault classification task. These two techniques allow the direct use of data without the need for front ends for signal pre-processing, as well as being able to handle multivariate and variable time series, such as signal sequences for the post-miss case. To develop the two proposed systems for classification, simulated data of short-circuit faults from the UFPAFaults public database were used. To compare results with methodologies already presented in the literature for the problem, the FBSC architecture was also evaluated for the same database. In the case of FBSC architecture, different front ends and classifiers were used. The comparative assessment was performed from the measurement of error rate, computational cost and statistical tests. The results showed that the HMM-based classifier was more suitable for the problem of classification of short circuits on transmission lines.
Acesso aberto (Open Access)
Análise de supraharmônicos em equipamentos eletrônicos e caracterização utilizando a transformada wavelet
(Universidade Federal do Pará, 2018-09-10) RODRIGUES, Carlos Eduardo Moreira; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
Esta dissertação objetiva analisar a emissão, a propagação e a interação entre equipamentos envolvendo componentes harmônicas que possuem frequência na faixa entre 2 kHz e 150 kHz, denominadas supraharmônicos. A literatura especializada já reportou a emissão de supraharmônicos por equipamentos eletrônicos como lâmpadas fluorescentes, lâmpadas LED, inversores de frequência e nobreaks, além de impactos relacionados ao aquecimento de cabos e terminações, ruído acústico e interferência em sistemas PLC (Power Line Communication). No presente trabalho, foram realizadas campanhas de medição, em ambiente laboratorial, em inversores de frequência e um conjunto de lâmpadas LED. As medições se dividiram em dois grupos distintos: com os equipamentos conectados à rede elétrica e a uma fonte eletrônica trifásica, com o objetivo de verificar as ordens e os níveis, tanto das emissões provenientes dos equipamentos, quanto da distorção emitida pela própria fonte eletrônica, além da interação entre a fonte e os equipamentos alimentados. Foram empregadas a Transformada de Fourier e a Transformada Wavelet Packet para efetuar a análise e caracterização das distorções observadas. As medições mostraram uma contribuição significativa dos equipamentos observados e da fonte eletrônica para a emissão de supraharmônicos, além da amplificação da distorção quando os equipamentos são por ela alimentados.
Acesso aberto (Open Access)
Análise dos impactos harmônicos em uma indústria de manufatura de eletroeletrônicos utilizando árvores de decisão
(Universidade Federal do Pará, 2015-03-27) NOGUEIRA, Rildo de Mendonça; SANTANA, Ádamo Lima de; http://lattes.cnpq.br/4073088744952858; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
The Power Quality (PQ) is constantly the subject of many studies, mainly those that are related to the industrial production sector, where are concentrated large loads of the electrical systems. With the evolution of industrial production processes and the introduction of new technologies in the industrial sector, quantities of electronic equipment bars were added that are sources of disturbances in the systems, and affecting the quality of the product "electricity". In order to minimize the inconvenience resulting from low quality of energy and damage to utilities and consumers (industrial, commercial and residential), it was developed in Brazil, distribution procedures in the national grid (PRODIST), created and developed the National Electric Energy Agency (ANEEL). The PRODIST aims to regulate and standardize activities related to energy distribution, including product quality standards. This work was concentrated and held in a company of the industrial pole of Manaus (PIM), which has a three-phase electrical system low voltage, in order to monitor the quality of the product "electricity" through the harmonic content generated by the electrical network involved in manufacturing. The data generated were subjected to computational intelligence technique (HF), using the process of knowledge extraction discovery in databases or KDD. The objective is to analyze, identify and diagnose the coupling points and processes that have representative harmonic content for the system, so being able to check how much each analyzed process may be affecting the power quality within the industry itself and the point of coupling with the concessionaire, through the generations of harmonic distortion, thus avoiding penalties and other sanctions regulated.
Acesso aberto (Open Access)
Avaliação da distorção harmônica total de tensão no ponto de acoplamento comum industrial usando o processo KDD baseado em medição
(Universidade Federal do Pará, 2018-03-27) OLIVEIRA, Edson Farias de; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
In the last decades, the transformation industry has provided the introduction of increasingly faster and more energy efficient products for residential, commercial and industrial use, however these loads due to their non-linearity have contributed significantly to the increase of distortion levels harmonic of voltage as a result of the current according to the Power Quality indicators of the Brazilian electricity distribution system. The constant increase in the levels of distortions, especially at the point of common coupling, has generated in the current day a lot of concern in the concessionaires and in the consumers of electric power, due to the problems that cause like losses of the quality of electric power in the supply and in the installations of the consumers and this has provided several studies on the subject. In order to contribute to the subject, this thesis proposes a procedure based on the Knowledge Discovery in Database - KDD process to identify the impact loads of harmonic distortions of voltage at the common coupling point. The proposed methodology uses computational intelligence and data mining techniques to analyze the data collected by energy quality meters installed in the main loads and the common coupling point of the consumer and consequently establish the correlation between the harmonic currents of the nonlinear loads with the harmonic distortion at the common coupling point. The proposed process consists in analyzing the loads and the layout of the location where the methodology will be applied, in the choice and installation of the QEE meters and in the application of the complete KDD process, including the procedures for collection, selection, cleaning, integration, transformation and reduction, mining, interpretation, and evaluation of data. In order to contribute, the data mining techniques of Decision Tree and Naïve Bayes were applied and several algorithms were tested for the algorithm with the most significant results for this type of analysis as presented in the results. The results obtained evidenced that the KDD process has applicability in the analysis of the Voltage Total Harmonic Distortion at the Point of Common Coupling and leaves as contribution the complete description of each step of this process, and for this it was compared with different indices of data balancing, training and test and different scenarios in different shifts of analysis and presented good performance allowing their application in other types of consumers and energy distribution companies. It also shows, in the chosen application and using different scenarios, that the most impacting load was the seventh current harmonic of the air conditioning units for the collected data set.
Acesso aberto (Open Access)
Avaliação operacional dos efeitos do perfil de demanda de quatro sistemas de microgeração fotovoltaica conectados à rede
(Universidade Federal do Pará, 2018-06-29) PARIJÓS JÚNIOR, Ivan Ruy de; PEREIRA, Edinaldo José da Silva; http://lattes.cnpq.br/9596575345034065; MACÊDO, Wilson Negrão; http://lattes.cnpq.br/3386249951714088
Power quality has been widely researched. Several phenomena that affect power quality, and its consequences, have been investigated. When the power quality theme involves the operation of a grid-connected photovoltaic system, the main concern is about the operation of the inverter, which is responsible for the interface of the photovoltaic generator with the grid. The introduction of photovoltaic generation in the grid requires attention on certain factors such as changes in the load curve, voltage level, harmonic components in the inverter current and variation on the power factor (PF) of the costumer. This work aims to test and evaluate some aspects that may influence the power quality due to the insertion of photovoltaic generation in the grid, associated whit the load demand. Four grid-connected photovoltaic systems were used to develop this work, as well as a data acquisition bench that was set up to monitor the operation of these systems. In this work it is possible to conclude that the operation of photovoltaic systems causes changes in the voltage level at the point of common coupling. Also, the interaction between photovoltaic systems and loads causes changes in the load profile measured by the side of the grid, causing the total harmonic distortion in the current (THDi) and PF measured at this side to be different from those measured at the loads and photovoltaic sides. It is possible to observe that the grid-connected photovoltaic system can contribute to increase or reduce the THDi seen by the local grid, where the greatest contribution of harmonic distortion in the current delivered by the grid is associated to the demand profile of the load.
Acesso aberto (Open Access)
Comparação entre regressão linear, redes neurais artificiais e árvores de regressão para quantificação do impacto harmônico de múltiplas cargas em redes elétricas de distribuição.
(Universidade Federal do Pará, 2018-11-19) PAIXÃO JÚNIOR, Ulisses Carvalho; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
In recent years, the socio-economic development of the population, the growth of commercial and industrial sectors, as well as the ever-increasing installation of new electrical loads, have generated great evolution in demand of electricity consumption. In turn, to obtain more efficient systems, the manufacturers have produced equipment more energy efficient for residential, commercial and industrial use. However, these loads due their non-linearities, have contributed significantly to the increase in harmonic distortion levels of voltage and current, raising the concern of the power sector managers with respect to the power quality, mainly, due to the difficulty in the identification of the origin of the harmonic distortion. Therefore, to anticipate the harmonic effects and meet the current legislation, through computational techniques, this work emphasis is placed on the common coupling point (CCP) of consumers and utility, regardless of consumption characteristics and loads, to assess the harmonic impacts in his grid, besides comparing the reliability level of the techniques through the mean absolute error (MAE). The proposed methodology uses the Electrical Power Quality System (SISQEE) software that allows the use of three different computational techniques, such as Linear Regression, Artificial Neural Networks and Regression Trees, to evaluate the harmonic contribution of each feeder at the point of interest of the chosen electric grid. To prove the validity of the methodology, two case studies, based on real measurements at a university and at an industrial district, was carried out with a minimum sampling period of seven days using power quality analyzers, according to the distribution procedures by ANEEL (PRODIST). As a result of the power quality, it was verified how much each feeder impacts the voltage and current distortion at the CCP, besides classifying the feeders in relation to their respective impacts in the studied electrical grid. Also, as a result, the studies allowed the evaluation of performance between the different techniques, with different time intervals (weekly, daily and per load level), allowing to classify the behavior and reliability of each technique in each period. As a conclusion of the work, the proposed methods and analyzes presented allow managers to perform a more efficient mitigation action of the harmonic impacts caused in the electrical network and, also, to identify the differences between the techniques and their degree of reliability, in accordance with the time intervals studied.
Acesso aberto (Open Access)
Desenvolvimento de um simulador de redes elétricas para estudos da propagação de harmônicos
(Universidade Federal do Pará, 2016-08-23) LIMA, Diorge de Souza; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813
The electricity sector in Brazil has faced many changes due to the modernization of electrical equipment, especially when it refers to residential consumers. This has provided a considerable increase in the level of harmonic distortion in the electric distribution networks, which can be explained by the large use of devices based on power electronics in an attempt to make them more efficient and compact. Therefore, it becomes necessary execute analysis of the levels of harmonic distortion in the power systems. Monitoring by power quality analyzer is the best way to collect data of the electrical system; however, the computer simulation is an efficient tool capable of reproducing the disturbances and behavior of the electric networks for different operating modes. Thus, this paper aims to present a computational environment that helps the harmonic propagation studies in electrical systems. For this, it was used the software ATP (Alternative Transient Program) for modeling the electrical system, the harmonic behavior of a nonlinear load is represented by effective values of harmonic currents in function of time. The measurements were obtained through power quality analysis of a distribution network in the North Region of Brazil. Thus, for this set of measures, a set of simulations was performed, providing for the users the values of harmonic voltages for all buses of the electrical system. Therefore, with the simulator of electrical networks it is possible perform harmonic propagation studies in several electrical systems, and it can work as a strategic planning tool for the use of mitigating measures or for the strategic control of harmonic distortion, from evaluations of most critical moments of harmonic distortion at all points of the network. To demonstrate its use, the industrial system of 13 bar was used as a test system for analysis in this dissertation.
Acesso aberto (Open Access)
Detecção, classificação e quantificação automática de variações de tensão de curta duração para aplicação em análise de pós-operação em sistemas de energia elétrica
(Universidade Federal do Pará, 2006-05-19) MACHADO, Raimundo Nonato das Mercês; PELAES, Evaldo Gonçalves; http://lattes.cnpq.br/0255430734381362; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813
The analysis of occurrences in electric power systems is of fundamental importance for secure operation of the system, and to maintain quality of the electric energy supplied to the consumers. The electric power utilities use equipments called disturbance registers (DR’s) for monitoring and diagnose of problems in the electric and protection systems. The waveforms usually analyzed in the electric power utilities operation centers, are those generated by events that usually cause the opening of lines due to circuitbreakers operation commanded by the protection devices. However, a great amount of stored data that can contain important information on the behavior and the performance of the system is not analyzed. The proposal of this work is to use the available data in electric power utilities control and operation centers obtained from DR’s equipments, to classify and quantify of automatic form signals that characterize power quality problems, such as, short duration voltage variations: sags, swells and interruptions. The proposed method uses wavelet transform to obtain a characteristic vector for voltages in phases A, B and C, and a probabilistic neural network is used for classification. The classified signals as presenting short-duration variation are quantified for duration and magnitude of the event, using the multiresolution decomposition signal analysis properties. Those parameters, then, will form a database where statistical procedures of analysis can be used to prepare reports regarding power quality features. The results obtained with the application of this proposed methodology to a real system are also presented.
Acesso aberto (Open Access)
Impactos na qualidade da energia elétrica provenientes do rápido crescimento da demanda no Sudeste do Estado do Pará
(Universidade Federal do Pará, 2012-03-15) ESTEVES, Eduardo Augusto Cardoso; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
In the recent years, the social and economical development in the Southeast of the State of Pará has been mainly caused by the exploitation and processing of mineral industries, which added to the population growth, has generated a high increase in the demand of electric energy and consumption due to the increasing installation of new industrial, commercial, residential and rural single-phase charges. This global increase is impacting directly the performance of distribution of electric utility, which can be expressed by the permanent disturbances caused by harmonics, such as buzzing in the power transformer and disruption of medium voltage conductors. These disturbances will be presented in a study of case involving the Substations (SE’s) Itacaiúna and Itupiranga. To prove how they can be harmful in these SE’s, campaigns of measurement were performed to obtain practical results and then, to perform studies involving simulations of short-circuit, load flow and spreading of harmonics in order to obtain an analytical diagnostic about the situations found and thus to issue recommendations to solve the problems identified. This study will provide a valuable support to the Concessionaire of Energy and it may be taken as a reference to the study of Power Quality in other substations, in addition to experimental basis for future charges from ANEEL, regarding the implementation of procedures in Electric Power Distribution National Electric System (PRODIST).
Acesso aberto (Open Access)
Metodologia de auxílio na tomada de decisão na formação de conjuntos de unidades consumidoras de energia elétrica
(Universidade Federal do Pará, 2010-10-08) SANTOS, Fábio Corrêa dos; SANTANA, Ádamo Lima de; http://lattes.cnpq.br/4073088744952858; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
The issue of Proceedings of Electric Power Distribution (PRODIST) confirmed the comparative analysis of the distribution companies of electricity established by Resolution 024/2000 as the basis for establishing the goals of continuity indicators DEC (Costomer Average Duration Interruption Index) and FEC (Costomer Average Frequency Interruption Index). The setting of targets is directly influenced by the definition of the sets of consumer units of the distribution companies of electricity is therefore of interest to the distribution companies a good definition of these sets. This work presents the development of a methodology based on machine learning techniques to assist companies in electric power distribution in decision making of the definition of sets of consumers units aimed at improving compatibility of the goals for the indications of DEC and FEC with reality assemblies in relation to environmental characteristics and of infrastructure of the concession area of the distribution company.
Acesso aberto (Open Access)
Otimização multiobjetivo da compensação de potência reativa em redes de distribuição considerando restrições de distorção harmônica
(Universidade Federal do Pará, 2014-11-14) AZEVEDO, Manoel Socorro Santos; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813
The localization of capacitors banks in the electric power distribution networks, correctly sized, looks for to compensate eventual excesses of circulation of reactive power for transmission lines, what implies the reduction of operational costs for the reduction of the energy losses and an increase of the capacity of transmission of active power assuring the established levels of voltage and power factor simultaneously. The proliferation of the nonlinear loads produced a change in the scenarios of study of the electric power systems due to the degradation effects that the harmonic generated by them cause about the quality of the electric power. Considering this new scenario, this thesis has as general objective to develop a computational tool using computational intelligence supported in genetic algorithms (GA), for the multiobjective optimization of the reactive power compensation in distribution electric networks able to locate and size in a good way the necessary compensation units to achieve the best economic benefits and the maintenance of the indexes of quality of the energy settled down by the Brazilian norms. As technological innovation of the work, the developed computational tool allows to optimize the compensation of the reactive power to improve the power factor in polluted distribution networks with harmonics that, differently of previous methods, not alone it uses capacitors banks, but also harmonic filters with that objective. The NSGA-II algorithm is used to determine optimal solutions of Pareto for the problem and it allows the specialist to determine the most effective solutions. The formulation proposed in this thesis for the solution of the problem presents several novelties being able to highlight that the achieved solution allows to determine the compensation of reactive power in systems with certain harmonic penetration, complying with pertinent standards of power quality, with respect to the tolerated levels of harmonic distortion.
Acesso aberto (Open Access)
Previsão de distorção harmônica em cargas residenciais utilizando redes neuro-fuzzy
(Universidade Federal do Pará, 2018-07-11) MORAIS JÚNIOR, Albino Moisés Faro de; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
This work presents a modeling for THDv%, THDi% and individual harmonics using predictions from an ANFIS system that learns with measured data and predicts the behavior of the network for future values. These forecasts can help meet national THDv% standards stipulated by the Agência Nacional de Energia Elétrica (ANEEL) through Distribution Procedures (PRODIST), such as THDi% international standards, thus anticipating the currently recommended standards, but in the near future will be punitive. The modeling is performed by means of a Neuro-Fuzzy system called ANFIS, which uses neural network to learn the behavior of the system and adjustment of the parameters and Fuzzy rule for the determination of the system output values taking into account the learning of the Neural network. The great advantage of this tool is the power of modeling standards using a prediction of the harmonic state of the connected loads in the low voltage, which helps in the creation of pseudomedidas for the distribution networks, where it is difficult and costly to obtain real measurements. Among the practical applications for this tool is the use of the predicted values instead of measured anomalous values, the use in energy meters to predict and avoid exceeding the values of Harmonic Distortion stipulated in standard and the use as a basis for the prediction of individual harmonics that can be used in harmonic load flow studies.
Acesso aberto (Open Access)
Projeto multicritério de filtros harmônicos passivos para instalações industriais utilizando técnicas de inteligência computacional
(Universidade Federal do Pará, 2013-05-29) LEITE, Jandecy Cabral; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
Due to the importance of the industrial growth in the North and in particular the Industrial Pole of Manaus (PIM), it is important to have mathematical tools that facilitate the expert decisions on the selection and sizing of harmonic filters needed to neutralize the harmful effects of harmonics generated by nonlinear loads of industry and achieve compliance with the power quality standards. Moreover, as the passive harmonic filters have the capacity to generate reactive power to the network, they are effective compensating reactive power means and therefore can achieve significant savings in sales of electric energy consumed by these industrial facilities. This thesis aims to develop a mathematical method and a computational tool for the selection of the configuration and the design parameters of a set of passive harmonic filters for industrial electrical systems. In this direction, the optimization problem of compensation of harmonics through passive filters is formulated as a multi-objective problem that considers both the goals of reducing harmonic distortion as the economic effectiveness of the project considering the characteristics of the Brazilian system of tariffs. Moreover, the presented formulation considers relevant restrictions imposed by the national and foreign standards. A computational solution to this problem was achieved using the NSGA-II genetic algorithm which determines a set of Pareto optimal solutions (Frontier) that enable the designer to choose the most appropriate solutions to the problem. Furthermore, the computational tool developed has several new features as: not only calculates the parameters that characterize the filters, but also selects the type of configuration and the number of branches of the filter in each candidate bus according to a set of predetermined settings; has implemented two standards for assessing the constraints of power quality (Prodist Modulo-8 and IEEE 519-92) that can be selected by the user; determines solutions with good performance indicators for various characteristic and non-characteristic scenarios of the system that allow to represent: the daily variations of the load as well as the variations of system parameters and filters; evaluates the cost of energy bills in a grid that has different industrial operating conditions (characteristic scenarios) and assesses the economic effect of harmonic filters as reactive power compensators. To develop the computational tool of this thesis, it was used a phase-coordinates model for the electric power grids of industrial and services installations to program additional computational tools. These tools comprise a frequency scan program, a harmonic power flow program for the harmonic current injection method and a fundamental frequency power flow program. The positive results of this thesis, from the analysis of several practical examples show the advantages of the developed method.
Acesso aberto (Open Access)
Sistema inteligente de suporte a análise da qualidade da energia elétrica em regime permanente
(Universidade Federal do Pará, 2017-02-21) ROCHA, Gabriel Vianna Soares; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148
This work presents the development of software that provides a computational environment so that the user can carry out analyzes of Quality of Eletrical Energy (QEE) following the rules stipulated by the National Eletrical Power Agency (ANEEL) through the Distribution Procedures (PRODIST). Also it is possible to do analysis of contribution of impacts caused by the injection of harmonics in the electric network, pointing out the possible percentage shares of contribution of each Consumer Unit (UC), through modules that perform a sensitivity study through Computational Intelligence (CI) techniques as Artificial Neural Network (ANN) Regression Trees (RT) and Simple Linear Regression (LR). For the construction of the models are used time series data of current and voltage harmonics that were obtained through measurement campaigns.