• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 32
  • 24
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 68
  • 68
  • 30
  • 28
  • 24
  • 20
  • 17
  • 15
  • 13
  • 12
  • 12
  • 11
  • 9
  • 9
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Metodologia de aplicação de geração distribuída fotovoltaica em baixa tensão nos reticulados subterrâneos das distribuidoras de energia elétrica / Operation of Photovoltaic Distributed Generation (DG) on Secondary Side of the Spot and Grid Network Distribution Systems

Barreto, Gustavo de Andrade 15 April 2014 (has links)
O objetivo deste estudo foi a elaboração e testes simulados, com dados elétricos reais, de metodologia para a operação de geração distribuída (GD) fotovoltaica, em baixa tensão e com exportação de excedentes, em sistemas de distribuição reticulado. A metodologia superou as limitações impostas pelos equipamentos de proteção chamados Protetores de Rede, inerentes à topologia de distribuição do tipo reticulado. Tais equipamentos inviabilizam a geração distribuída, que exporta excedentes para a rede externa por desconectarem os transformadores de média para baixa tensão, causando o ilhamento da GD, sempre que existir um fluxo de potência reverso, ou seja, no sentido do cliente para a concessionária. O objetivo foi alcançado por meio da criação de um simulador de subestação de reticulado exclusivo (Spot) de três transformadores nos qual os comportamentos dos protetores de rede eram testados com dados de fluxo de potência reais aquisitados em subestações de reticulado em Brasília (concessionária CEB) e em subestação do Instituto de Energia e Ambiente (IEE), da Universidade de São Paulo, onde existe uma instalação geradora fotovoltaica de 12kWp. Novos comportamentos dos protetores de rede foram simulados para compatibilizar tal fluxo reverso de potência e parâmetros críticos foram levantados. Nas simulações, encontraram-se caminhos viáveis de promover estas conexões com segurança e simplicidade. Estes novos comportamentos podem ser implementados no firmware dos relés de protetores de redes microprocessados. / The aim of this study was to develop and test a methodology for operation of photovoltaic distributed generation (DG) on secondary side of the Spot and Grid Network types of electricity distribution systems, allowing for the export of excess energy. This methodology did overcome the limitations imposed by the protective equipment known as Network Protector (NP), a standard equipment on secondary network distribution topology. Such equipments make exporting energy from distributed generation systems to the grid unfeasible because of the operational aspects of Network Protectors. This devices will disconnect the transformers whenever there is a reverse power flow, i.e. towards the utility, causing the islanding of the DG. The objective was achieved through the conception of a simulator for a Spot Network substation with three transformers where the behaviors of network protectors could be tested. Those simulations were performed with actual power flow data from real network substations in Brasilia city (CEB utility area) and the substation at the Institute for Energy and Environment (IEE) at the University of Sao Paulo, where a photovoltaic generating facility of 12kWp exists. New behaviors were simulated in order to make the NPs to manage the expected reverse power flow successfully. The most important parameters for the model were explained. Viable ways to connect exporting photovoltaic DG to secondary networks safely and simply have been found by means of these simulations. These new behaviors could be embedded in the firmware of the NP´s microprocessor based relays.
42

Análise da eficiência técnica relativa de empresas brasileiras distribuidoras de energia elétrica: uma abordagem DEA

Rempel, Cristiano 14 November 2014 (has links)
Submitted by Maicon Juliano Schmidt (maicons) on 2015-04-27T17:10:28Z No. of bitstreams: 1 Cristiano Rempel.pdf: 802687 bytes, checksum: 0da97154db93c5073c586acabccf6507 (MD5) / Made available in DSpace on 2015-04-27T17:10:28Z (GMT). No. of bitstreams: 1 Cristiano Rempel.pdf: 802687 bytes, checksum: 0da97154db93c5073c586acabccf6507 (MD5) Previous issue date: 2014-01-14 / Nenhuma / Essa dissertação tem como objetivo principal analisar a eficiência técnica relativa de empresas brasileiras distribuidoras de energia elétrica. A busca por eficiência tem sido uma constante em muitos setores e tem crescido em vista do maior grau de competição e das pressões sociais por melhor aproveitamento de recursos. Entre estes, o setor de energia elétrica tem sido demandado a oferecer crescente desempenho que possa apoiar o ciclo de desenvolvimento econômico do país. A técnica de pesquisa utilizada é o levantamento ou survey, classifica-se como descritivo, com abordagem quantitativa, realizado com base em dados de 2012. Utilizando a metodologia de Análise Envoltória de Dados (DEA) foi possível mensurar a eficiência técnica relativa das empresas selecionadas, identificar os determinantes da eficiência dessas unidades, definir as unidades benchmarks, bem como os percentuais de melhorias. A partir da aplicação DEA e com base no rol de variáveis selecionadas, identificou-se que são eficientes tecnicamente sete empresas dentre as 18 concessionárias de distribuição de energia elétrica brasileiras da amostra, sendo elas: CPFL-PI, CEMAR, ELETROPAULO, COELCE, RGE, COSERN e CPFL-PA. A empresa RGE é o melhor benchmark para as empresas ineficientes, detentora de diferentes prêmios de qualidade e gestão do setor. Por fim, o que contribuiu para os escores de eficiência das empresas foi a variável Potência Instalada, tendo como melhorias potenciais para as empresas ineficientes principalmente as variáveis Extensão da Rede, Número de Empregados e o Tempo Médio de Atendimento. / This dissertation has as main objective to analyze the relative technical efficiency of Brazilian electricity distribution companies. The quest of efficiency has been constant in many sectors and has grown due to the greater degree of competition and social pressures for better utilization of resources. Among these, the electricity sector has been prosecuted to offer increased performance that can support the cycle of economic development of the country. The technique used is the survey, ranks as descriptive, quantitative approach carried out based on 2012 data. Using the methodology of Data Envelopment Analysis (DEA) was possible to measure the relative efficiency of the selected companies, to identify the determinants of the efficiency of these units, set the benchmark units and the percentage of improvement. From the DEA application and based on the list of selected variables, there were identified seven technically efficient companies, among 18 dealers of Brazilian electricity distribution in the sample, namely: CPFL-PI, CEMAR, ELETROPAULO, COELCE, RGE, COSERN and CPFL-PA The company RGE is the best benchmark for inefficient firms, holder of different awards of quality and management of the sector. Finally, contributing to the efficiency scores of companies was the variable Installed Capacity, with the potential improvements for inefficient firms mainly consisting of variables Network Extension, Number of Employees and Average Time of Service.
43

[en] EFFECTIVENESS OF A TECHNOLOGICAL SOLUTION FOR REDUCING ELECTRICAL ENERGY PILFERAGE IN DISTRIBUTION COMPANIES: A CASE STUDY / [pt] EFICÁCIA DE SOLUÇÃO TECNOLÓGICA PARA REDUÇÃO DE FURTOS DE ENERGIA ELÉTRICA EM EMPRESAS DISTRIBUIDORAS: ESTUDO DE CASO

CLAUDIA ZUCCOLOTTO REIS 03 March 2006 (has links)
[pt] As perdas de energia elétrica, particularmente as comerciais, constituem problema importante e complexo para as empresas distribuidoras. O problema só se apresenta de forma aguda nos países em desenvolvimento, onde o percentual de perdas por furto é elevado e adquire importantes conotações sociais, políticas e culturais. Isso explica o fato de empresas brasileiras de distribuição de energia elétrica investirem recursos apreciáveis para mitigar esse problema e ressalta a importância de um tema ainda pouco explorado na literatura técnico-científica. Esta dissertação, de caráter exploratório, tem como objetivo estudar o problema de perda de energia por desvio e a eficácia de soluções tecnológicas investigando o caso de uma empresa e os resultados obtidos em projeto recente. Ao tempo do estudo, a empresa implantava uma tecnologia cujo objetivo principal era identificar os clientes que desviam energia elétrica e, posteriormente, tornar o processo de faturamento automatizado. O estudo partiu de algumas questões julgadas mais relevantes, incluindo: Quanto a empresa ganhou com a instalação desta tecnologia? Como se comporta o consumo dos clientes antes e depois da instalação da tecnologia? Há correlação entre o ganho da empresa e o poder aquisitivo da população da área? Há efeito demonstração de uma área sobre suas vizinhas? A partir destas questões foram analisadas séries de dados referentes ao consumo medido antes e após a instalação da nova tecnologia. Os resultados indicam a viabilidade da tecnologia como eficaz paliativo de curto-prazo para o problema cuja solução definitiva envolve tratamento concomitante dos aspectos sociais, políticos e culturais. / [en] Electrical energy losses, chiefly, commercial losses, constitute an important and complex problem for energy distribution companies worldwide. However, only in developing countries the problem becomes acute because theft losses are large, and coupled with social, legal, political and cultural issues. This explains why Brazilian energy distribution companies dedicate sizable investments for mitigating the problem, and stresses the importance of a theme still largely unexplored in the technical-scientific literature. This thesis, of exploratory nature, addresses the problem and assesses the effectiveness of technological solutions by investigating the case of a recent project developed in a Brazilian company. At the time of the research, the company was implementing a new and original technology, whose main objective was to identify pilfering clients, and later on, to make the billing process more automated. The study started with some questions judged more relevant, including: How large was the gain yielded by the new technology? How does the energy consumption behave after the technological change? Is there a correlation between the gain obtained and the areas of lesser purchasing power? Is there a demonstration effect upon neighboring areas? Starting from these questions, series of historical data on measured consumption before and after the new technology were analyzed. The results indicate the feasibility of the technology as an effective shortterm palliative for the problem whose ultimate solution involves the concurrent treatment of the social, legal, political e cultural aspects.
44

Use of the CIM framework for data management in maintenance of electricity distribution networks

Nordström, Lars January 2006 (has links)
Aging infrastructure and personnel, combined with stricter financial constraints has put maintenance, or more popular Asset Management, at the top of the agenda for most power utilities. At the same time the industry reports that this area is not properly supported by information systems. Today’s power utilities have very comprehensive and complex portfolios of information systems that serve many different purposes. A common problem in such heterogeneous system architectures is data management, e.g. data in the systems do not represent the true status of the equipment in the power grid or several sources of data are contradictory. The research presented in this thesis concerns how this industrial problem can be better understood and approached by novel use of the ontology standardized in the Common Information Model defined in IEC standards 61970 & 61968. The theoretical framework for the research is that of data management using ontology based frameworks. This notion is not new, but is receiving renewed attention due to emerging technologies, e.g. Service Oriented Architectures, that support implementation of such ontological frameworks. The work presented is empirical in nature and takes its origin in the ontology available in the Common Information Model. The scope of the research is the applicability of the CIM ontology, not as it was intended i.e. in systems integration, but for analysis of business processes, legacy systems and data. The work has involved significant interaction with power distribution utilities in Sweden, in order to validate the framework developed around the CIM ontology. Results from the research have been published continuously, this thesis consists of an introduction and summary and papers describing the main contribution of the work. The main contribution of the work presented in this thesis is the validation of the proposition to use the CIM ontology as a basis for analysis existing legacy systems. By using the data models defined in the standards and combining them with established modeling techniques we propose a framework for information system management. The framework is appropriate for analyzing data quality problems related to power systems maintenance at power distribution utilities. As part of validating the results, the proposed framework has been applied in a case study involving medium voltage overhead line inspection. In addition to the main contribution, a classification of the state of the practice system support for power system maintenance at utilities has been created. Second, the work includes an analysis and classification of how high performance Wide Area communication technologies can be used to improve power system maintenance including improving data quality. / QC 20100614
45

Aspects industriels de la gestion de tension et la capacité d'accueil de la génération photovoltaïque dans les réseaux basse tension / Industrial aspects of voltage management and hosting capacity of photovoltaic power generation in low voltage networks

Rauma, Kalle 29 March 2016 (has links)
Dans cette thèse, les mesures de tension fournies par l'infrastructure de comptage avancé (Advanced Metering Infrastructure, AMI) sont utilisées pour contrôler un régleur en charge situé à la sous station HTA/BT. La thèse présente une méthode simple permettant de sélectionner les clients basse tension pour lesquels les mesures de tension sont utilisées comme une entrée au contrôleur du régleur en charge. Le procédé mis au point tient compte de la charge et de la topologie du réseau. En outre, une méthode simple pour créer des courbes réalistes et statistiquement correctes pour les études de réseaux est présenté. Les méthodes créées ont été testées en utilisant des données réelles de réseaux basse tension sur un logiciel très utilisé dans le secteur de la distribution d'électricité ont conduit à des résultats encourageants; quelques clients par réseau basse tension doivent être surveillés afin d’estimer avec une grande précision où se situe les extremums de tension sur le réseau.Cette méthodologie est également utilisée pour estimer la capacité d'accueil de génération d'énergie photovoltaïque dans un réseau à basse tension donné.Dans la première partie, l'évolution de la capacité d'accueil en utilisant trois types de contrôle de tension différents; un régleur en charge de cinq et neuf positions et le contrôle de la tension à travers les générateurs photovoltaïques, sont étudiés. L'étude considère deux cas différents pour le placement et le dimensionnement des générateurs photovoltaïques dans un réseau basse tension. Les résultats sur 38 réseaux basse tension sont fournis.Dans la deuxième partie, les capacités d'accueil de 631 réseaux basse tension, situés dans une région métropolitaine française, sont analysés en utilisant un régleur en charge de cinq et neuf positions.Le travail a été réalisé en collaboration avec Électricité Réseau Distribution France (ERDF), le principal opérateur du réseau de distribution français. Toutes les études présentées dans la thèse reposent sur les données réelles de fonctionnement normal. En outre, toutes les études sont mises en œuvre sur un logiciel largement utilisé dans l'industrie de la distribution d'énergie.Comme une partie introductive aux réseaux basse tension, la thèse fournit une vue générale sur le système électrique français. De plus, la thèse présente un certain nombre de technologies sélectionnés en tenant compte des réseaux basse-tension qui semblent prometteurs pour le futur. / In this thesis, voltage measurements provided by the advanced metering infrastructure (AMI) are used to control an on-load tap changer located at the secondary substation. The thesis presents a practical and a straightforward method of selecting the low voltage customers whose voltage measurements are used as an input to the controller of the on-load tap changer. The developed method takes into account the load and the topology of the network. Furthermore, a simple method of creating synthetic and statistically correct load curves for networks studies is presented. The created methods have been tested by using real data of low voltage networks on a common platform in the power distribution industry leading to encouraging results; a few customers per low voltage network should be monitored in order to achieve accurate voltage measurements.This methodology is further applied to estimate the hosting capacity of photovoltaic power generation in a given low voltage network.In the first part, the evolution of the hosting capacity by using three different types of voltage control; an on-load tap changer of five and nine tap positions and voltage control through photovoltaic power generators, is studied. The study considers two different cases for placing and sizing the photovoltaic generators in a low voltage network. The results of 38 low voltage networks are provided.In the second part, the hosting capacities of 631 low voltage networks, located in a French metropolitan area, are analysed by using an on-load tap changer of five and an on-load tap changer of nine tap positions.The work has been together with Électricité Réseau Distribution France (ERDF), the major French distribution system operator. All studies presented in the thesis are based on the real operational data of the company. Moreover, all studies are implemented on a platform that is widely used in the power distribution industry.As an introductory part to low voltage networks, the thesis provides a general view about the French power system. In addition, the thesis presents a number of selected technologies considering low voltage networks that seem promising in the future.
46

Market potential for using demand response from heat pumps in multi-family buildings

Grill, Rebecca January 2018 (has links)
More renewable energy leads to higher energy imbalances in the Swedish electric power system. In the same time, the grid capacity is almost reached in some regions which requires an extension of the current grids or a reduction of the power consumption. Demand response could be a key factor for both stabilizing the energy balances and reducing the grid congestion. The aim with this thesis is to analyze the potential incomes that demand response from heat pumps can generate for the balance responsibility parties and the grid operators and evaluate how it would affect the end-consumers.   The investigated local grid that contains of 174 multi-family buildings with heat pumps could reduce its highest peak power with 2,9 MW. This peak power reduction generated a cost reduction of 483 000 SEK per year or 2800 SEK per building per year in reduced penalty fees and power subscription fees. The mFRR market and the power reserve market were determined to be the most suitable markets for using demand response from heat pumps on for the balance responsibility party in the electricity price region SE3. SE3 consists of 10146 multi-family buildings with heat pumps. The mFRR market generated an average income of 2 699 000 SEK per winter season whereas the power reserve market generated a yearly administrative compensation of 1 133 000 SEK per season and 104 000 SEK per call-off. It is important that end-consumers obtain demand-based tariffs or hourly based tariffs to enable a cost reduction from the control system.
47

The Pending Agenda of the Electricity Sector / La Agenda Pendiente del Sector Eléctrico

Dammert Lira, Alfredo 10 April 2018 (has links)
This article discusses the structure of the electricity supply. This system mainly consists of three subsystems: the generation, transmission and distribution of electricity. Each system is comprised of different features like its regulation. Given the above, the author tells us the Peruvian case, on the body called the Committee of Economic Operation of the System (COES). / El presente artículo trata sobre la estructura de la provisión de electricidad. Este sistema consta principalmente de tres subsistemas: la generación, la transmisión, y la distribución de electricidad. Cada sistema está conformado por diferentes características al igual que su regulación. Ante lo mencionado, el autor nos comenta el caso peruano, sobre el organismo llamado Comité de Operación Económica del Sistema (COES).
48

Uma eficiente metodologia para reconfiguração de redes de distribuição de energia elétrica usando otimização por

Prieto, Laura Paulina Velez January 2015 (has links)
Orientador: Prof. Dr. Edmarcio Antonio Belati / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2015. / Esta pesquisa apresenta uma metodologia para reconfiguração de sistemas elétricos de distribuição baseada na metaheurística "otimização por enxame de partículas" do inglês Particle Swarm Optimization, denominada por PSO. Na metodologia proposta, inicialmente são estabelecidos os subconjuntos de chaves candidatas, calculados com base no número de chaves abertas necessárias para manter a radialidade do sistema. Assim, o espaço de busca diminui consideravelmente. O algoritmo de solução foi desenvolvido para minimizar as perdas de potência nas linhas da rede de distribuição, sujeita às seguintes restrições: a) limite de tensão; b) ilhamento de carga; c) radialidade do sistema e d) balanço das potências ativa e reativa nos nós da rede. Alterações na formulação clássica do PSO foram realizadas de modo a tornar o processo de busca mais eficiente. O processo de busca que compõem a metodologia foi detalhado em um sistema de 5 barras e 7 linhas. A técnica foi validada em quatro sistemas: 16 barras e 21 chaves; 33 barras e 37 chaves; 70 barras e 74 chaves; e 136 barras e 156 chaves. Comparando os resultados para os quatro sistemas testados com os resultados existentes na literatura, em todos os casos foi encontrada a topologia com o menor número de perdas já encontrada na literatura consultada até o momento. / This research presents a method for network reconfiguration in distribution systems based on the metaheuristics "Particle Swarm Optimization". In this method, the candidate switch subsets are calculated based on the number of open switches necessary to maintain the radial configuration. Then, the search space reduces substantially. The algorithm was developed to minimize the power losses in the lines of the distribution system considering the following constrains: a) voltage limits; b) load connectivity; c) radial configuration and d) power balancing. The original version of PSO was modified to improve the search process. The search process that composes the methodology is detailed in a system of 5 nodes and 7 switches. The technique was validated in four systems: 16 nodes and 21 switches, 33 nodes and 37 switches and 70 nodes and 74 switches and 136 nodes and 156 switches. Comparing the results for the four systems tested with existing literature results in all cases showed the topology with fewer losses already found in the literature to date.
49

Analýza zranitelnosti elektrizační soustavy České republiky / Czech electricity grid vulnerability analysis

MICHALEC, Jan January 2017 (has links)
Acts of terrorism are used by various individuals, groups and transnational networks to push forward own political views, ideas and ideology on society whilst using multiple forms of violence. Their acts of violence are able to jeopardize and endanger health and safety of peoples, environment and the vitality of critical infrastructure as well. Nowadays the most spelled threat comes from so called foreign fighters whose destabilized and war-torn countries of origin are located in Northern Africa and Middle East. In combination with inefficient management of illegal migration phenomenon and unsatisfactory EU policies on that matter the problem becomes even more amplified. Schengen Area provides EU-members with non-restrictive border regime which fosters migration and trade by a great deal but on the other hand it creates an enormous security risk in terms of terrorism and its prevention. For that matter there should be much more emphasis added to the management of EU outside borders. The second most problematic issue are the matters of radicalization of individuals and minority groups in the EU. There might be a causal relationship between growing rates of frustration between peoples and social marginalization of noted societal groups which might be caused by unsatisfactory assimilation policies of respective EU member states. The goal of this given thesis was to analyze risks to Czech electrical grid which might be posed by an act of terrorism. The analysis was done by breaking down the electrical grid safety measures into respective sectors and parts. Risk for each particular category were analyzed and final risk assessment whilst using help of security professionals. A questionnaire method was used to complete this particular task. The questionnaire dataset was later used to identification of most vulnerable weak-points in the electricity transmission system of the Czech Republic in respect to acts of terrorism. This diploma thesis might be used as a blueprint for improvements in the security management of the Czech electricity transmission system and for educatory purposes at the University of South Bohemia, at the Faculty of Health and Social Sciences.
50

O equilíbrio econômico-financeiro das distribuidoras de energia elétrica brasileiras nas demonstrações contábeis / The economic and financial equilibrium of Brazilian electricity distribution companies in the accounting reports

Cibelle Maria do Amorim Ferreira 23 March 2009 (has links)
Este trabalho analisa a potencialidade da contabilidade na identificação do equilíbrio econômico-financeiro dos contratos de concessão de distribuição do setor elétrico brasileiro. São apresentadas as abordagens da contabilidade regulatória do setor em questão, o novo ambiente contábil societário estabelecido pela lei 11.638/2007 e a Medida Provisória 449/2008, que altera a legislação societária vigente, a fim de fornecer elementos teóricos para discussão do papel da contabilidade na regulação econômica. Especial ênfase é dada aos subsídios contábeis na determinação e manutenção do equilíbrio econômico-financeiro dos contratos de concessão do serviço de distribuição de energia elétrica no Brasil, para identificar como estes podem conter restrições à adoção de um novo modelo de contabilidade. A análise procura investigar a contabilidade regulatória como instrumento de regulação econômica do setor de distribuição de energia elétrica para entender sua contribuição na identificação do equilíbrio econômico-financeiro estabelecido pelo marco regulatório do setor elétrico nacional, haja vista a mudança estabelecida pela Lei 11.638/2007. Para tanto, a metodologia utilizada é uma pesquisa analítica e comparativa através da simulação de um contrato de concessão de acordo com o modelo contábil atual e o novo modelo com a aplicação das interpretações internacionais de contabilidade. Conclui-se que o modelo elaborado de acordo com as normas internacionais de contabilidade proporciona melhor identificação do equilíbrio econômico e financeiro estabelecido nos contratos de concessão. / This work analyzes the accounting potentiality in the identification of the economic and financial equilibrium of the distribution concession contracts of Brazilian electrical sector. The regulatory accounting approaches of the mentioned sector are presented, the new business accounting environment established by law 11.638/2007 and the law 449/2008, which alters the effective partnership law, in order to provide theoretical elements to discuss the role of accounting in economic regulation. Especial emphasis is given to account subsidies when determining and maintaining the economic and financial equilibrium of concession contracts for electricity distribution service in Brazil, to identify how they may be restrictive to the adoption of a new accounting standard. The analysis tries to investigate the regulatory accounting as an economic regulation tool of the electricity distribution sector to understand the identification of the economic and financial equilibrium established by the regulatory mark of national electricity sector, have seen the change of the law 11.638/2007. Therefore, the methodology used is analytical and comparative research through simulation of a concession contract according to the effective accounting model and the new model applying accounting international standards. It was concluded that the model elaborated according to international accounting standards provides better identification of economic and financial equilibrium established in concession contracts.

Page generated in 0.4389 seconds