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  • 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.
101

Repotencialização de linhas de transmissão localizadas em áreas de severas restrições ambientais. / Uprating of transmission lines in areas of severe environmental constrains.

Giardinetto, Rosemary Boettger 24 September 2014 (has links)
Os cerca de 107.000 km de linhas de transmissão existentes no Brasil, nas tensões de 138/230/345/440/500/750 kV (corrente alternada), e 600 kV (corrente continua), atravessam parques nacionais ou estaduais, estradas, rios e parte se encontra com sobrecarga. O aumento da capacidade de carregamento das linhas de transmissão, se feito da forma tradicional, com a substituição ou reforço nas estruturas e fundações, em faixas que cruzam áreas consideradas de preservação ambiental permanente, exige obras adicionais que alteram o meio ambiente e desta forma, com os rigores da atual legislação ambiental, torna inviável tais alterações ou substituição. Uma das formas encontradas é a utilização de novas tecnologias em cabos condutores aéreos. Este trabalho tem a finalidade de pesquisar as necessidades do recondutoramento da linha de transmissão, com a minimização/eliminação dos danos ao meio ambiente. Uma das alternativas encontradas é a utilização de cabos especiais, que por se tratar de nova tecnologia em cabos, e considerando o desconhecimento de seu desempenho efetivo em condições reais, surge a necessidade da verificação de seu comportamento. Este trabalho apresenta a análise de casos no Brasil e o desenvolvimento piloto de um sistema de monitoramento em tempo real, através de medições diretas e indiretas, no trecho de linha de transmissão onde foi instalado um condutor de nova tecnologia, a fim de acompanhar o desempenho das características elétricas e mecânicas do novo condutor. Como resultado final foram validados os valores de projeto da ampliação da capacidade da linha de transmissão, sem impactos ao meio ambiente. / The approximately 107,000 km of transmission lines existing in Brazil, operating at 138 kV, 230 kV, 345 kV, 440 kV, 500 kV, 750 kV(ac) and 600 kV(dc), regularly encounter and cross state or national parks as well as highways, rivers and parks. Due to the ever increasing demand of power most of these transmission lines are at present overloaded. Increasing the loading capacity of these transmission lines in the traditional way (i.e. by substituting or reinforcing the structures and foundations in areas of permanent preservation) require additional works that may alter the environment; thus, making unfeasible the application of such alterations in view of the current strict environmental regulations. One way to cope with such a problem is through the utilization of new technologies applied to cables. Therefore, the objective of this work is to investigate the alternative of reconductoring a transmission line causing a minimum damage (and if possible eliminating this damage) to the environment. One of the alternatives found is the use of special cables which due to its relatively new introduction and technology to the power industry demands a thorough study on issues like the performance and verification of its behavior under real conditions. This work presents the development of a real-time monitoring system through direct and indirect measurements performed on a transmission line segment where a special conductor was installed. During the course of the research the performance of the new conductor regarding its electrical and mechanical characteristics was monitored. The measurements performed showed to be coherent with those obtained during the design of the transmission line.
102

[en] CORPORATE GOVERNANCE: ANALYSIS OF BOARD OF DIRECTORS COMPOSITION IN THE BRAZILIAN ELECTRICAL ENERGY SECTOR / [pt] GOVERNANÇA CORPORATIVA: ANÁLISE DA COMPOSIÇÃO DO CONSELHO DE ADMINISTRAÇÃO NO SETOR DE ENERGIA ELÉTRICA DO BRASIL

RENATA SILVA DE ALMEIDA 25 May 2012 (has links)
[pt] A composição dos conselhos de administração é um dos temas mais recorrentes em governança corporativa, uma vez que os conselheiros representam os mediadores no conflito de agência. O objetivo desta dissertação foi avaliar, no setor de energia elétrica, se a composição dos conselhos como tamanho, presença feminina, proporção de conselheiros independentes e diferentes indivíduos nos cargos de diretor executivo e presidente do conselho afetam o valor e o desempenho das empresas do setor. Com uma amostra de 38 companhias do setor no período de 2005 a 2010, os resultados das regressões em painel apontam que o tamanho do conselho de administração mostrou-se positivamente relacionado a valor e desempenho com a presença de uma faixa ótima de conselheiros. A independência do conselho também apresentou relação positiva com valor e desempenho. No entanto, não houve significância estatística para a variável de valor. A porcentagem de mulheres no conselho não apresentou relação positiva com desempenho e a presença de pessoas distintas nos cargos de diretor executivo e presidente do conselho de administração apresentou resultados contraditórios em relação a valor e desempenho. / [en] Board of directors composition is one of the most common themes in corporate governance because directors represent the mediators in the agency conflict. The aim of this work was to analyze in the energy sector if the board composition such as board size, women participation, proportion of independent directors and different people in the positions of CEO and Chairman affect value and performance. With a sample of 38 companies from 2005 to 2010, the results of panel regressions show that board size was positive related to value and performance with an optimal range of directors. Board independence was also positive related with performance. There was no significant statistical relation to the value variable. Proportion of women in the boards was not positive related with value and performance and different people in the positions of CEO and Chairman showed contradictory results on value and performance.
103

Dálkový sběr dat po silových vedeních / Remote data acquisition over the power lines

Neuschl, Martin January 2009 (has links)
The subject of this paper is „remote data acquisition over the power lines“. The first part is engaged in characteristics of power lines. The other part considers PLC technology, its properties and usage. Base on disturbance and noise in power grid is chosen optimal modulation technique and error handling for PLC. The next part describes options of authentication. It has been designed secure way of authentication for data collection over power lines and attack-resistance is considered as well. Practical purpose is dedicated to simulations and noise measuring during communication of narrowband PLC modems. It deals with long-term power grid testing and its influence on transmission rate between PLC modems and also with the influence on primary parameters of power grid. Packets are investigated during communication as well.
104

Návrh vzdáleného řízení malé vodní elektrárny / Small Hydropower Plant Remote Control Project

Šarman, Luděk January 2012 (has links)
The thesis focuses on a proposal of making maintenance and control of a small hydroelectric power station more effective. It is adjusted to the concrete situation and contains a selection of management, suitable technology, design of network infrastructure and description of an active element configuration with an appropriate proposition of financing. Then the final directions for installation and usage of a remote control system of the power station are presented as the result of this thesis.
105

Obchodování elektrické energie v soudobých podmínkách České republiky / Trading of Electricity in the Current Conditions of the Czech Republic

Lomjanský, Michal January 2015 (has links)
This diploma thesis deals with trading of electricity in the current conditions of the Czech Republic. First it defines the theoretical and legal aspects of the electricity market and introduces several basic terms related to the given topic such as producer, electricity dealer, end user etc. Then it analyses selected areas of an electricity dealer’s activities directed at optimization of his/her business strategy concerning electrical energy trading in the current conditions of the Czech energy market.
106

Análise de sensibilidade através de um modelo implicitamente acoplado para alívio de sobrecargas em redes de transmissão /

Hoji, Eduardo Shigueo. January 2006 (has links)
Orientador: Antonio Padilha Feltrin / Banca: Jose Roberto Sanches Mantovani / Banca: Ariovaldo Verandio Garcia / Resumo: A reestruturação dos mercados de energia para fornecer livre acesso ao sistema de transmissão e o conseqüente aumento no número de transações de compra e venda de energia tem causado congestionamento nos sistemas de transmissão. Como conseqüência, as redes têm sofrido sobrecargas nas linhas de maneira mais freqüente. Uma maneira prática de se melhorar a capacidade de transferência de potência ativa em uma linha de transmissão é a redução de seu fluxo reativo. Esse controle pode ser feito através de alterações nos controles das fontes de potência reativa e nos taps de transformadores. A definição de quais ações serão tomadas de modo a minimizar o fluxo reativo e aliviar, ou mesmo eliminar, a sobrecarga em uma determinada linha, pode ser realizada através da análise de sensibilidade. Uma vez que se está interessado na resposta do sistema às variações de injeções de reativos, utilizamos a matriz Lc do método CRIC (Calcul de Reseaux Implicitement Couples) de fluxo de potência. Também foi utilizado o modelo constante do método CRIC. A metodologia desenvolvida consiste da manipulação da matriz Lc com outras sensibilidades de primeira ordem, de modo a se obter as sensibilidades entre fluxo reativo nas linhas e injeção de reativos nas barras e fluxo reativo nas linhas e taps dos transformadores. As sensibilidades obtidas fornecem as barras e transformadores mais indicados para alívio de uma determinada sobrecarga e são úteis principalmente em casos emergenciais, nos quais não seja necessária a instalação de novas fontes de reativos. Os resultados obtidos são comparados com os obtidos através de uma metodologia semelhante, que utiliza a matriz jacobiana do método de Newton. Foram utilizados para os testes o sistema Cigré de 32 barras, e o sistema Sul-Sudeste brasileiro em duas configurações de carga diferentes. / Abstract: The restructuring of energy markets to supply free access to the transmission system and the consequent increase of the number of power transactions has been causing congestions in the transmission systems. As consequence, the networks have been suffering overloads in the lines in a more frequent way. A practice way of improving the transfer capability of active power in a transmission line is to decrease its reactive power flow. That control can be made through changes in the reactive power sources injections and in the transformer ratios of transformers. The definition of which actions will be taken to minimize the reactive flow and to alleviate, or even to eliminate, the overload in a determined line can be accomplished through the sensibility analysis. Once it is interested in the answer of the system to the variations of reactive power injections, we used the matrix Lc from the CRIC (Calcul of Reseaux Implicitement Couples) power flow method. The constant model of CRIC is also used. The developed methodology consists of the manipulation of the matrix Lc with other first order sensibilities, in order to obtain the sensibilities among reactive flow in the lines and reactive power injections in the buses and reactive flow in the lines and transformer ratios of the transformers. The obtained sensibilities indicate the buses and transformers for relieving a certain overload and they are mainly useful in emergency cases, which it is not necessary the installation of new sources of reagents. The obtained results are compared with the obtained through a similar methodology, that uses the of Newton's method jacobian matrix. The methodologies were tested using the 32-bus Cigré network and the South-southeast Brazilian system in two different load configurations. / Mestre
107

Investigation on solar powered organic Rankine cycle with energy storage, economic and environmental benefits at different climate zones in various buildings types in the United States of America

Hemmati, Hadis 25 November 2020 (has links)
This study investigates the potential of installing an integrated solar powered Organic Rankine Cycle (ORC) with electric energy storage (EES) to provide clean energy to commercial buildings in different climate zones in the US. Reducing the primary energy consumption (PEC), lowering the carbon dioxide emissions (CDE) and increasing the operational cost savings are primary objectives. Firstly, a large office building for eight US climates is studied. The EES is sized to store all the electricity generated by the system. Secondly, the system is studied for sixteen different commercial buildings, in the best climate zone, by considering two operational strategies. Finally, the influence of variable expander efficiency on the system performance is investigated. Results indicate that Phoenix is the best location in the US, among the evaluated locations, to install the ORC-EES. The model for the full-service restaurant shows higher savings and more electricity supply percentage than the other buildings. The model under the variable expander efficiency lowers the yearly PEC by 1.6% and CDE and operational cost savings both by 11%.
108

Energy performance regulations and methodologies of energy saving in office buildings in southern Europe

Tsave, A. January 2009 (has links)
The Directive 2002/91/EC of the European Parliament and Council on energy performance of buildings entered into force on 4th January 2003, setting the minimum requirements of energy performance. All Member States had to incorporate the requirements of the new directive in national legislation by January 2006 and build up relevant systems and measures to transpose and implement these requirements. The stage of Directive’s implementation in the countries of Southern Europe is reported because of the similar climatic conditions and the geographical location for a future enforcement in Greece, as the building code in Greece is still under development. As energy use in buildings accounts for about 40% of the final energy demand in the European Union, the application of building standards can achieve a reduction in electric energy consumption and therefore an increase in energy performance of buildings. A record of the electric energy consumption of office buildings in the four Prefectures of Crete is implemented aiming at a future energy saving, which may be obtained by either through increased efficiency or by reducing electric energy consumption.
109

[en] ADJUSTING LOAD SERIES BY THE CALENDAR AND TEMPERATURE EFFECTS / [pt] AJUSTE DAS SÉRIES DE CARGA DE ENERGIA ELÉTRICA INFLUENCIADAS PELOS OFENSORES CALENDÁRIO E TEMPERATURA

THIAGO GOMES DE ARAUJO 08 January 2015 (has links)
[pt] O objetivo do presente trabalho é a geração de uma série mensal de carga elétrica livre das variações de calendário e de temperatura. Para tal, foram comparadas duas abordagens, uma totalmente empírica e outra híbrida com métodos empíricos e modelagens de regressão dinâmica, para identificar a mais adequada para a retirada desses ofensores. Os dados utilizados são provenientes de observações diárias de cada um dos quatro subsistemas que integram o Sistema Interligado Nacional (SIN), porém a ideia é produzir séries mensais do SIN e não apenas de cada um dos subsistemas. A série trimestral do PIB foi utilizada para decidir qual abordagem melhor ajustou os dados de Carga. A série mensal de carga ajustada do SIN será utilizada para subsidiar decisões, de compra e venda de energia nos leilões, das empresas distribuidoras de energia elétrica. / [en] This thesis proposes a method to generate monthly load series free of variations coming from two sources: calendar and temperature. Two approaches were considered, one totally empirical and another one called hybrid, as it use empirical procedure to remove the calendar effect and a dynamic regression type of model to remove the temperature effects. The data set used comes found to daily observations from each one of the four subsystems that form the SIN (Brazilian Integrated Grid). However the final task is to obtain a unique monthly series for the SIN and not only the four subsystems monthly series. The quarterly PIB series was used to check the performance of the two proposed methods. Such adjusted series are quite important tools to hold on the decision of acquisitions and dailes of energy in the energy audits.
110

Curvas típicas de carga para o planejamento operacional do sistema de distribuição. / Typical load curves for operational planning of distribution systems.

Paula, Guilherme Marques de Faria 25 April 2006 (has links)
Nesta dissertação é proposto e avaliado um modelo de caracterização da carga para utilização no planejamento operacional dos sistemas de distribuição baseado na caracterização dos consumidores através de curvas típicas de carga. A identificação dos padrões de curvas típicas baseou-se na aplicação da rede neural tipo mapa auto organizável, sobre a grande massa de dados de medições de clientes da campanha de medidas realizada pela distribuidora no processo de revisão tarifária o que permitiu a identificação dos padrões de consumo de energia ativa e fator de potência para os consumidores ao longo do dia. O módulo de agrupamento baseado no mapa auto organizável associado a técnica clássica de agrupamento das k-médias mostrou-se uma ferramenta extremamente robusta e eficaz na identificação de padrões para grandes bases de dados. A comparação dos resultados das estimativas de carga para cerca de 200 alimentadores de distribuição medidos através do sistema SCADA complementa e valida a aplicação desta metodologia, que culmina com a proposição de um modelo de otimização, que com base nas medições, possibilita melhorias significativas na estimativa de carga dos alimentadores estudados. A metodologia proposta neste trabalho demonstra ser uma ferramenta eficaz para que a distribuidora de energia elétrica possa constantemente realimentar os dados sobre os hábitos de consumo de seus clientes, garantindo assim a manutenção de estimativas consistentes para o planejamento operacional de seu sistema de distribuição. / This dissertation presents and validate a load characterization framework for the operational planning of electric distribution networks based on characterization of customer typical load curves. The pattern recognition of typical load curves was based on the usage of self organizing maps, a type of neural network, over the huge database of customer field measurements performed by the electric energy utility for tariff review process, allowing the characterization of daily active energy consumption and power factor behaviors. The grouping module is based on self organizing map technique along with classic k-means technique, which proved to be an extremely effective tool for pattern recognition over large databases. The results of load estimation for 200 distribution feeders measured by SCADA system ensures the quality and accuracy of this framework which presents also an optimization model based on such measures, resulting significant improvement on load estimation for these feeders. This framework proves to be an effective tool for electric energy utilities for constant evaluation of customer’s power consumption behavior, allowing the maintenance of accurate estimations for operational planning of distribution networks.

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