No description available.

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Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references and index.

Thesis (M. Phil.)--University of Hong Kong, 1993.

Thesis (doctoral)--University of Newcastle, 1990.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 157-163). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 17, 2009) Includes bibliographical references (p. 67-70).

Orientador: Maria Cristina Dias Tavares / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-10T09:40:09Z (GMT). No. of bitstreams: 1 MestasValero_Patricia_M.pdf: 3064250 bytes, checksum: 898053aa51c68fc5e5e170f255fa1d05 (MD5) Previous issue date: 2007 / Resumo: As sobretensões em um sistema de transmissão não podem ser evitadas assim como a sua total supressão é extremamente difícil, entretanto, suas amplitudes podem ser reduzidas. Tradicionalmente, as sobretensões transitórias advindas das manobras de energização e religamento de linhas de transmissão são limitadas utilizando o ¿método convencional¿ como é o caso do uso de resistores de pré-inserção, este apesar de ser um método efetivo, apresenta uma aceitação de sua tecnologia tendente a diminuir devido ao alto custo de implementação e manutenção. Nos últimos tempos as principais empresas de transmissão do mundo têm se mostrado mais favoráveis a utilização de pára-raios e chaveamento controlado de disjuntores para o controle de sobretensões, mas na prática esta aplicação está apenas sendo iniciada. O presente trabalho foi realizado com o objetivo de analisar os diferentes métodos para o controle de sobretensões associadas às manobras de energização e religamento trifásico de linhas de transmissão em vazio determinando assim as melhores condições técnicas para a otimização destes processos. Apresentam-se os resultados obtidos através de simulações com o programa PSCAD/EMTDC de um caso específico com dados reais dos geradores, transformadores, características dos trechos de linhas de transmissão, pára-raios e reatores de compensação em derivação tendo como base um sistema de 500 kV / Abstract: The switching transient in transmission system cannot be prevented as well as its total suppression is extremely difficult, however, its magnitudes have to be limited. For long transmission lines, traditionally the switching transient overvoltages due to energization and reclosure are limited by the ¿conventional method¿ as is the case of preinsertion resistors in the line circuit breakers. Although this is an effective mitigation method it presents a decreasing acceptance due to the high cost of implementation and maintenance. Recently, important transmission firms in the world have shown the trend to the use of surge arresters and controlled switching breakers, in practical this application is only being initiated. The present work was realized with the objective of analyzing the different methods for the overvoltages control associates to energization and three-phase reclosing maneuvers of transmission lines to determine the best technique for the optimization of these processes. The results was obtained through digital simulations with PSCAD/EMTDC software for an specific case with real dates for generators, transformer, transmission lines, surge arresters and shunt compensation reactors of a 500 kV system / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Orientador: Maria Cristina Dias Tavares / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T12:17:57Z (GMT). No. of bitstreams: 1 Montanari_AllanAlves_M.pdf: 7585929 bytes, checksum: 4c00ba94f40e488cc4da50c4089e8630 (MD5) Previous issue date: 2009 / Resumo: Este trabalho apresenta um esquema de religamento monopolar adaptativo rápido para otimizar o tempo compreendido entre a abertura e o religamento da fase sob falta. A proteção adaptativa recompõe rapidamente o sistema de transmissão de energia elétrica, minimizando a probabilidade de propagação de perturbações severas no sistema. O método é fundamentado na análise de dados de ensaios de arco secundário gerados e monitorados numa estrutura de testes construída em campo, composta por um trecho real de linha de transmissão (três torres e dois vãos). Analisou-se o conteúdo harmônico da tensão e da corrente de arco secundário através da aplicação da Transformada de Fourier Janelada. Tais análises viabilizaram a realização de um tratamento estatístico para a caracterização da assinatura harmônica de arco secundário. Simulações de faltas monofásicas foram realizadas utilizando dados provenientes dos Ensaios de arco secundário. Desenvolveu-se um algoritmo baseado nas características Harmônicas da tensão da fase sob falta, calculadas através do deslocamento de uma janela de tempo sobre os sinais analisados (Transformada de Fourier Janelada). O algoritmo determina a existência do arco secundário e fornece informações a respeito do instante no qual o religamento pode ser realizado com sucesso. O método apresenta também um mecanismo para a detecção da característica permanente ou transitória da falta. / Abstract: This work presents a fast adaptive single-phase autorec1osingseheme to optimize the period between the tripping operation and the rec10sure of the faulted phase breakers. The adaptive proteetion quiekly reeomposes the eleetric power transmission, minimizing the probability of severe damages propagation in the system. The method is based on the analysis of secondary are field tests data that were generated and monitored in an infra-structure which consists of a real transmission line section (three towers and two spans). The harmonic content of the secondary are voltage and eurrent was analyzed by the application of Short Time Discrete Fourier Transform. Such analysis made it possible to implement a statistical approach in order to obtain the secondary are harmonic signature. Single-phase faults computer simulations were performed using the data obtained from the secondary are tests. It was developed an algorithm based on the voltage harmonic content of the faulted phase, which was ea1culated by shifting a window on the analyzed signals (Short Time Discrete Fourier Transform). The algorithm determines the secondary are existence and provides information in order to suceessfully rec10se the circuit breaker. The method also presents a control mechanism responsible for identifying whether the fault is a permanent one or a transient fault. / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Transient stability analysis is an important part of power system planning and operation. For large power systems, such analysis is very demanding in computation time. On-line transient stability assessment will be necessary for secure and reliable operation of power systems in the near future because systems are operated close to their maximum limits. In the last two decades, a vast amount of research work has been done in the area of fast transient stability assessment by direct methods. The major difficulties associated with direct methods are the limitations in the power system model, determination of transient stability regions and adaptation to changes in operating conditions. In this thesis catastrophe theory is used to determine the transient stability regions. Taylor series expansion is used to find the energy balance equation in terms of clearing time and system transient parameters. The energy function is then put in the form of a catastrophe manifold from which the bifurcation set is extracted. The bifurcation set represents the transient stability region in terms of the power system transient parameters bounded by the transient stability limits. The transient stability regions determined are valid for any changes in loading conditions and fault location. The transient stability problem is dealt with in the two dimensions of transient stability limits and critical clearing times. Transient stability limits are given by the bifurcation set and the critical clearing times are calculated from the catastrophe manifold equation. The method achieves a breakthrough in the modelling problem because the effects of exciter response, flux decay and systems damping can all be included in the transient stability analysis. Numerical examples of one-machine infinite-bus and multi-machine power systems show very good agreement with the time solution in the practical range of first swing stability analysis. The method presented fulfills all requirements for on-line assessment of transient stability of power systems. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate