Este trabalho apresenta uma metodologia de tratamento e análise baseada em medições de tensões e correntes com conteúdo harmônico para avaliar a contribuição de harmônicos dos elementos da rede elétrica baseando-se somente nas medições sincronizadas de alguns pontos da rede. Os métodos de análise propostos neste trabalho consistem em análises por correlação entre as correntes harmônicas de dois locais diferentes, utilizando os registros semanais de valores eficazes das correntes harmônicas medidas, buscando identificar as linhas de transmissão que possuem o mesmo comportamento de correntes harmônicas quanto a sua variação semanal em amplitude e em análises de fasores medidos nestes locais para determinar os fluxos de correntes sobre as barras do sistema. Para demonstrar o método, é apresentado um estudo de caso de uma campanha de medição feita pelo Operador Nacional do Sistema e pela Universidade de São Paulo, nos anos de 2007 e 2008, sobre as correntes de 5ª harmônica que sobrecarregavam os filtros na Subestação de Ibiúna. O método foi utilizado para investigar as origens dessas correntes no sistema de alta tensão. Os resultados da análise por correlação indicaram as linhas de transmissão com maior contribuição para as correntes absorvidas pelos filtros. Essas correntes são originárias de duas subestações e foi possível detectar a influência dos cabos subterrâneos ligados a estas subestações na amplificação destas correntes. Análises fasoriais nas subestações ao longo dos corredores estudados serviram para validar os resultados obtidos da análise por correlação e uma simulação do fenômeno de ressonância harmônica foi realizada, confirmando a suspeita de amplificação das correntes de 5ª harmônica nos cabos subterrâneos. / This MSc thesis presents a methodology of treatment and analysis based on measurements of harmonic voltage and current to evaluate the harmonic contribution of the network elements in power systems based only on synchronized measurements of few points in the network. The method consists in a correlation analysis of weekly recordings of RMS values of harmonic currents measurements, to identify power lines that present the same behavior in harmonic currents regarding their weekly variation in amplitude. Another approach performs a phasor analysis of currents measured to determine current flows incoming some specific network buses. In order to demonstrate the method, a case study is considered, which consists in a measurement campaign carried out by the ISO and the University of São Paulo, in the years of 2007 and 2008, on the pattern of 5th harmonic currents that overload the filters installed at the Ibiúna Substation. The method was used to investigate the origins of these currents at the high voltage system. The outcome of the correlation analysis indicated the transmission lines with greater contribution to the currents absorbed by the filters. These currents originate from two substations and it was also detected the influence of underground cables connected to these substations in the amplification of these currents. Phasor analysis in substations applied to the studied power lines validated the results obtained from correlation analysis and a simulation of the phenomenon of harmonic resonance was performed, bringing confirmation of the amplification of the 5th harmonic current on the underground cables.

No description available.

Este trabalho apresenta uma metodologia de tratamento e análise baseada em medições de tensões e correntes com conteúdo harmônico para avaliar a contribuição de harmônicos dos elementos da rede elétrica baseando-se somente nas medições sincronizadas de alguns pontos da rede. Os métodos de análise propostos neste trabalho consistem em análises por correlação entre as correntes harmônicas de dois locais diferentes, utilizando os registros semanais de valores eficazes das correntes harmônicas medidas, buscando identificar as linhas de transmissão que possuem o mesmo comportamento de correntes harmônicas quanto a sua variação semanal em amplitude e em análises de fasores medidos nestes locais para determinar os fluxos de correntes sobre as barras do sistema. Para demonstrar o método, é apresentado um estudo de caso de uma campanha de medição feita pelo Operador Nacional do Sistema e pela Universidade de São Paulo, nos anos de 2007 e 2008, sobre as correntes de 5ª harmônica que sobrecarregavam os filtros na Subestação de Ibiúna. O método foi utilizado para investigar as origens dessas correntes no sistema de alta tensão. Os resultados da análise por correlação indicaram as linhas de transmissão com maior contribuição para as correntes absorvidas pelos filtros. Essas correntes são originárias de duas subestações e foi possível detectar a influência dos cabos subterrâneos ligados a estas subestações na amplificação destas correntes. Análises fasoriais nas subestações ao longo dos corredores estudados serviram para validar os resultados obtidos da análise por correlação e uma simulação do fenômeno de ressonância harmônica foi realizada, confirmando a suspeita de amplificação das correntes de 5ª harmônica nos cabos subterrâneos. / This MSc thesis presents a methodology of treatment and analysis based on measurements of harmonic voltage and current to evaluate the harmonic contribution of the network elements in power systems based only on synchronized measurements of few points in the network. The method consists in a correlation analysis of weekly recordings of RMS values of harmonic currents measurements, to identify power lines that present the same behavior in harmonic currents regarding their weekly variation in amplitude. Another approach performs a phasor analysis of currents measured to determine current flows incoming some specific network buses. In order to demonstrate the method, a case study is considered, which consists in a measurement campaign carried out by the ISO and the University of São Paulo, in the years of 2007 and 2008, on the pattern of 5th harmonic currents that overload the filters installed at the Ibiúna Substation. The method was used to investigate the origins of these currents at the high voltage system. The outcome of the correlation analysis indicated the transmission lines with greater contribution to the currents absorbed by the filters. These currents originate from two substations and it was also detected the influence of underground cables connected to these substations in the amplification of these currents. Phasor analysis in substations applied to the studied power lines validated the results obtained from correlation analysis and a simulation of the phenomenon of harmonic resonance was performed, bringing confirmation of the amplification of the 5th harmonic current on the underground cables.

Orientador: André Nunes de Souza / Banca: Pedro da Costa Junior / Banca: Geraldo Francisco Burani / Resumo: O sistema de transmissão é responsável por conectar os geradores de energia aos consumidores de forma segura e confiável sendo necessária sua constante ampliação para conseguir transportar as crescentes quantidades de energia elétrica. Nesta dissertação é realizada uma análise da situação atual e do processo de planejamento da expansão do sistema de transmissão brasileiro, assim como um estudo de caso sobre as modificações necessárias para a conexão da Usina de Belo Monte. Uma ferramenta de otimização da expansão do sistema de transmissão foi desenvolida, utilizando o método de modelagem do fluxo de carga linearizado e os algoritmos genéticos como técnica de solução, tendo como objetivo a simulação do impacto de diferentes cenários no custo da expansão da transmissão. A ferramenta proposta foi utilizada para simular os efeitos da presença de geração distribuída na expansão de um sistema de transmissão fíctício, onde foi constatado uma clara tendência de queda no investimento necessário para expansão do sistema de transmissão em resposta a índices crescentes de geração distribuída / Abstract: The transmission system is responsible for connecting the power generators to consumers safely and reliably. Its constant expansion is necessary to fit the transportation of increasing amounts of electricity. In this dissertation and analysis of the current configuration and the process of planning expansion of the Brazilian transmission system is provided. A tool to optimize the expansion of the transmission system was developed using the the linearized load flow modeling method and genetic algorithms. This tool was created to simulate the impact of different scenarios on the cost of transmission expansion planning. The proposed tool used to simulate the effecs of the presence of distributed generation in the expansion of a fictious transmission system, where it was found a clear downward trend in the total investment required for expansion of the transmission system as a function of the increasing levels of distributed generation / Mestre

This thesis describes a digital control system used by the Network Analog Group of the Bonneville Power Administration. This system, the Random Sequence Closing Control System, provides automatic control for a special purpose analog computer used in the study of switching surge over voltages on power transmission lines. This system, which uses pseudorandom data, has made it feasible to analyze switching surge phenomena on a statistical basis.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 163-170).

In the future, space solar power transmission and wireless power transmission will play an important role in gathering clean and infinite energy from space. The rectenna, i.e., a rectifying circuit combined with an antenna, is one of the most important components in the wireless power transmission system. To obtain high power and high output voltage, the use of a large rectenna array is necessary. Many novel rectennas and rectenna arrays for microwave and millimeter-wave wireless power transmission have been developed. Unlike the traditional rectifying circuit using a single diode, dual diodes are used to double the DC output voltage with the same circuit layout dimensions. The rectenna components are then combined to form rectenna arrays using different interconnections. The rectennas and the arrays are analyzed by using a linear circuit model. Furthermore, to precisely align the mainbeams of the transmitter and the receiver, a retrodirective array is developed to maintain high efficiency. The retrodirective array is able to track the incident wave and resend the signal to where it came from without any prior known information of the source location. The ultra-wideband radio has become one of the most important communication systems because of demand for high data-rate transmission. Hence, ultra-wideband antennas have received much attention in mobile wireless communications. Planar monopole ultra-wideband antennas for UHF, microwave, and millimeter-wave bands are developed, with many advantages such as simple structure, low cost, light weight, and ease of fabrication. Due to the planar structures, the ultra-wideband antennas can be easily integrated with other circuits. On the other hand, with an ultra-wide bandwidth, source power can be transmitted at different frequencies dependent on power availability. Furthermore, the ultra-wideband antenna can potentially handle wireless power transmission and data communications simultaneously. The technologies developed can also be applied to dual-frequency or the multi-frequency antennas. In this dissertation, many new rectenna arrays, retrodirective rectenna arrays, and ultra-wideband antennas are presented for microwave and millimeter-wave applications. The technologies are not only very useful for wireless power transmission and communication systems, but also they could have many applications in future radar, surveillance, and remote sensing systems.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 139-145).

Thesis--M. Phil., University of Hong Kong, 1986.

The demand for electrical energy in industrialised countries continues to increase steadily. As a result of this growing demand for electrical energy, there is a need for optimisation of the power system in terms of transmission and control. One option could possibly be an increase in transmission facilities to handle the increase in growth; however factors such as environmental issues as well as the possible cost incurred could hamper this particular approach. An alternative resides in loading the existing transmission network beyond its present operating region but below its thermal limit, which would ensure no degradation of the system. For this approach to be realised, improved control of the flow of power in an interconnected network would be advantageous so as to prevent unwanted loop flows and inadvertent overloading of certain lines. This approach can be made possible by the use of Flexible AC Transmission Systems (FACTS) technology. The concept of FACTS incorporates power-electronic compensation devices that can be typically used in an ac power system to enhance the system's power transfer and controllability. There exists a number of FACTS devices, where each device can be utilised differently to achieve the broad objective. One such device is the Thyristor Controlled Series Capacitor (TCSC). The TCSC is a class of FACTS device that makes it possible to alter the net impedance of a particular transmission line in an effort to force the flow of power along a "contract path". This thesis identifies, in the published literature, a set of strategies for the scheduling of power flow by use of variable compensation; such strategies are then considered in more detail in the analysis of the thesis. Firstly, a detailed dynamic model of a TCSC is developed together with its various controls and associated circuitry within the power systems simulation package PSCAD. In addition to this, a power flow controller scheme is then implemented, which exhibits the functionality of the power flow controller strategies reviewed in the literature. In order to test the validity and operation of the TCSC model as well as the analysis of the power flow controller scheme, a single-machine infinite bus (SMIB) study system model is developed and used as part of the investigation. This thesis, firstly, presents a theoretical analysis of two particular modes of power flow control in an interconnected ac transmission system. Secondly it confirms the results of an analytical study in previously published work with the implementation of the two control modes, and further extends the scope of the previous study by examining the impact of the power flow controller's design on the small-signal and transient stability characteristics of the study system. The key findings of this extended investigation are that the power flow controller's mode of operation has an important influence on both small-signal and transient stability characteristics of a power system: in partiCUlar, it is shown that one mode can be detrimental while the other beneficial to both system damping and first swing stability. Finally, the thesis applies the understanding of the power flow controller's operation obtained from the SMIB study system to the problem of inter-area mode oscillations on a well-known, two-area, multi-:generator study system. Real-time simulator results are presented to exhibit the effect of the power flow controller modes and controller design on the oscillatory characteristics of the two-area study system. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005