Thesis (M. Tech. Electrical engineering) -- Central University of technology, Free State, 2012 / Infrared thermography is a non-contact method of identifying the thermal behaviour of various plant equipment and machines, including their components, qualitatively via pattern recognition and quantitatively via statistical analysis. This allows for the development of condition monitoring and predictive failure analysis. It is well established that optimized maintenance planning can be more effective when a problem is detected in the early stages of failure. For example, in electrical systems an elevated electrical resistance caused by loose or corroded connections, broken conductor strands and dirty contact surfaces, results in localized heating, and a unique infrared pattern when analysed leads to the location of the problem and an indication of its severity. In recent years industrial thermography has used infrared detectors in the long wave portion of the electromagnetic spectrum normally between 8μm and 15μm, due partly to the fact that these wavelengths are not susceptible to solar radiation and/or solar glint. A number of scientific experiments were carried out on test apparatus to improve the understanding of the impact of convection, ambient air temperature and relative humidity on resultant infrared thermal images. Two similar heat sources, simulating a hotspot, at different temperature settings were used to determine whether the hotspot temperature should also be considered in conjunction with the atmospheric elements. The need for these experiments has also been identified by EPRI (Electrical Power Research Institute) in the USA as necessary to develop international severity criteria, and it is hoped that this study will contribute to this goal.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

O mundo moderno está cada dia mais conectado por todos os meios tecnológicos que existem hoje. Isto permite que mais e mais pessoas possam se comunicar, tornando a estrada da comunicação virtual obrigatória para a sobrevivência das pequenas, médias e grandes empresas públicas e privadas. O grande avanço tecnológico do século 20 foi à utilização em grande escala do PC (personal computer) comumente chamados de microcomputadores. Este avanço também chegou aos sistemas elétricos de potência, tornando as subestações digitalizadas. Estas subestações sendo digitais correm riscos de invasão cibernética interna ou mesmo externa. Embora a possibilidade de invasão cibernética externa seja pequena, ela existe. Diante dessa situação este trabalho propõe a aplicação de um sistema de segurança, aplicado em um sistema elétrico de potência. O trabalho concentra-se especificamente no estudo dos sistemas de detecção de intruso (SDI), nos seus dois modos básicos: o SDI por abuso e SDI por anomalia utilizando redes neurais artificiais. Estes conceitos serão testados em um sistema elétrico de potência simulado, com uma rede de comunicação baseada em microcomputadores e/ou equipamentos microprocessados, com relés digitais reais. Os Softwares, denominados SNORT e Carcará, foram utilizados e extensivamente testados com resultados altamente encorajadores para a função descrita. / Modern world is more connected each day by all technological means available. This allows more people to communicate, turning the virtual communication road obligatory to the survival of small, medium and large companies, whether public or private. The great technological advance of the 20th century was the large use of the PCs (personal computer), usually called microcomputers. This advance also reached the power electric systems with the digitalization of the substations. These digitalized substations, run the risk of cybernetic invasion, internal or even external. Although the possibility of external cybernetic invasion is small, it exists. In that context, the present thesis proposes the application of a security system for an electric power system. The focus will be the study of intruder detection systems (IDS), on its two basic forms: the IDS by abuse and the IDS by anomaly, using artificial neural networks. These concepts will be tested in a simulated electric power system, with a communication network based on microcomputers, with actual digital relays with the digitalization of the substations.

<p>We present a detailed study on application of factor<br />graphs and the belief propagation (BP) algorithm to the<br />power system state estimation (SE) problem. We start<br />from the BP solution for the linear DC model, for which<br />we provide a detailed convergence analysis. Using BPbased<br />DC model we propose a fast real-time state<br />estimator for the power system SE. The proposed<br />estimator is easy to distribute and parallelize, thus<br />alleviating computational limitations and allowing for<br />processing measurements in real time. The presented<br />algorithm may run as a continuous process, with each<br />new measurement being seamlessly processed by the<br />distributed state estimator. In contrast to the matrixbased<br />SE methods, the BP approach is robust to illconditioned<br />scenarios caused by significant differences<br />between measurement variances, thus resulting in a<br />solution that eliminates observability analysis. Using the<br />DC model, we numerically demonstrate the performance<br />of the state estimator in a realistic real-time system<br />model with asynchronous measurements. We note that<br />the extension to the non-linear SE is possible within the<br />same framework.<br />Using insights from the DC model, we use two different<br />approaches to derive the BP algorithm for the non-linear<br />model. The first method directly applies BP methodology,<br />however, providing only approximate BP solution for the<br />non-linear model. In the second approach, we make a key<br />further step by providing the solution in which the BP is<br />applied sequentially over the non-linear model, akin to<br />what is done by the Gauss-Newton method. The resulting<br />iterative Gauss-Newton belief propagation (GN-BP)<br />algorithm can be interpreted as a distributed Gauss-<br />Newton method with the same accuracy as the<br />centralized SE, however, introducing a number of<br />advantages of the BP framework. The thesis provides<br />extensive numerical study of the GN-BP algorithm,<br />provides details on its convergence behavior, and gives a<br />number of useful insights for its implementation.<br />Finally, we define the bad data test based on the BP<br />algorithm for the non-linear model. The presented model<br />establishes local criteria to detect and identify bad data<br />measurements. We numerically demonstrate that the<br />BP-based bad data test significantly improves the bad<br />data detection over the largest normalized residual test.</p> / <p>Glavni rezultati ove teze su dizajn i analiza novih<br />algoritama za re&scaron;avanje problema estimacije stanja<br />baziranih na faktor grafovima i &bdquo;Belief Propagation&ldquo; (BP)<br />algoritmu koji se mogu primeniti kao centralizovani ili<br />distribuirani estimatori stanja u elektroenergetskim<br />sistemima. Na samom početku, definisan je postupak za<br />re&scaron;avanje linearnog (DC) problema kori&scaron;ćenjem BP<br />algoritma. Pored samog algoritma data je analiza<br />konvergencije i predloženo je re&scaron;enje za unapređenje<br />konvergencije. Algoritam se može jednostavno<br />distribuirati i paralelizovati, te je pogodan za estimaciju<br />stanja u realnom vremenu, pri čemu se informacije mogu<br />prikupljati na asinhroni način, zaobilazeći neke od<br />postojećih rutina, kao npr. provera observabilnosti<br />sistema. Pro&scaron;irenje algoritma za nelinearnu estimaciju<br />stanja je moguće unutar datog modela.<br />Dalje se predlaže algoritam baziran na probabilističkim<br />grafičkim modelima koji je direktno primenjen na<br />nelinearni problem estimacije stanja, &scaron;to predstavlja<br />logičan korak u tranziciji od linearnog ka nelinearnom<br />modelu. Zbog nelinearnosti funkcija, izrazi za određenu<br />klasu poruka ne mogu se dobiti u zatvorenoj formi, zbog<br />čega rezultujući algoritam predstavlja aproksimativno<br />re&scaron;enje. Nakon toga se predlaže distribuirani Gaus-<br />Njutnov metod baziran na probabilističkim grafičkim<br />modelima i BP algoritmu koji postiže istu tačnost kao i<br />centralizovana verzija Gaus-Njutnovog metoda za<br />estimaciju stanja, te je dat i novi algoritam za otkrivanje<br />nepouzdanih merenja (outliers) prilikom merenja<br />električnih veličina. Predstavljeni algoritam uspostavlja<br />lokalni kriterijum za otkrivanje i identifikaciju<br />nepouzdanih merenja, a numerički je pokazano da<br />algoritam značajno pobolj&scaron;ava detekciju u odnosu na<br />standardne metode.</p>

Este trabalho propõe um novo método de proteção de geradores síncronos baseado em inteligência artificial, mais especificamente lógica fuzzy, com o propósito de melhorar a proteção destes componentes vitais aos sistema elétricos de potência. Um sistema elétrico de potência completo composto por geradores, linhas de transmissão e cargas foi simulado através do Real Time Digital Simulator para fornecer dados para realização de testes e validação do algoritmo de proteção inteligente. Adicionalmente, foram desenvolvidos dois esquemas experimentais que proporcionaram a obtenção de um conjunto extensivo de ensaios de faltas internas em dois geradores síncronos reais, com o objetivo de fornecer dados para comprovar a eficácia da proteção proposta. Um sistema integrado de software e hardware cujo objetivo é servir de plataforma para desenvolver e executar em tempo real algoritmos de proteção aplicados foi desenvolvido. Esse sistema integrado foi utilizado nos testes embarcados em tempo-real do algoritmo de proteção desenvolvido. Apresenta-se também um arranjo composto por funções de proteção tradicionais mais utilizadas em campo, as quais serviram como base de comparação de desempenho para o esquema de proteção inteligente desenvolvido. Os resultados apresentados mostram que o método de proteção inteligente proposto é mais sensível para detectar instantaneamente faltas fase-terra em geradores síncronos com aterramento de alta-impedância, além de ser capaz de identificar faltas entre-espiras e entre-caminhos / This work presents the development of a synchronous generator protective technique based on artificial intelligence, specifically fuzzy logic, in order to improve the protection of these vital components of the electric power system. A complete electric power system composed of generators, transmission lines and loads was simulated using the Real Time Digital Simulator to provide data for testing and validating the intelligent protection algorithm. Additionally, an extensive set of internal fault experiments conducted on two actual synchronous generators provided oscillograms to demostrate the proposed protection effectiveness. An integrated hardware and software system whose purpose is to serve as a platform for developing and executing real-time protection algorithms is presented. This integrated system was used for real-time embedded testing of the protection algorithm developed. An arrangement composed of traditional protection functions most used in the field is also presented, this arrangement served as a comparison basis for the intelligent protection scheme performance. The results show that the intelligent protection is more sensitive to detect instantly ground faults in synchronous generators with high-impedance grounding, it is also shown that the proposed scheme is able to identify inter-turns and inter-circuits faults

Submitted by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-24T11:43:12Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) A influência da resolução espacial em modelos de previsão em mesoescala na programação de despacho da produção de usinas eólicas.pdf: 2764488 bytes, checksum: 81db7c3fde344866addede3ebc92a198 (MD5) / Approved for entry into archive by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-24T11:44:33Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) A influência da resolução espacial em modelos de previsão em mesoescala na programação de despacho da produção de usinas eólicas.pdf: 2764488 bytes, checksum: 81db7c3fde344866addede3ebc92a198 (MD5) / Made available in DSpace on 2017-01-24T11:44:33Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) A influência da resolução espacial em modelos de previsão em mesoescala na programação de despacho da produção de usinas eólicas.pdf: 2764488 bytes, checksum: 81db7c3fde344866addede3ebc92a198 (MD5) Previous issue date: 2014-07-01 / O uso da energia eólica para produção de eletricidade tem crescido em todo o mundo. De acordo com o PDE 2023 (Plano Decenal de Expansão Energia) disponibilizado pela EPE (Empresa de Pesquisa Energética) a capacidade instalada provinda de energia eólica em 2013 foi de 2,2 GW, cerca de 1,8% da matriz energética brasileira. A perspectiva de aumento para 22,4 GW, que em 2023 representará cerca de 11,8% da matriz energética brasileira. Com isso, a necessidade de se ter uma programação da disponibilidade de energia de parques eólicos se torna extremamente importante na operação do sistema elétrico brasileiro. Usando os dados de velocidade de vento gerados pelo modelo WRF com resoluções espaciais de 15 km e 5 km a 100 m de altura fez-se a estimativa de geração de energia para os complexos eólicos de Cerro Chato e Osório no período de 9 de agosto de 2014 a 29 de agosto de 2014. Então comparou-se com os dados de programação diária de produção de energia feitos pelas usinas, pelo modelo ETA e com os de geração real, do mesmo período, fornecidos pelo Operador Nacional do Sistema em seus boletins semanais. No período de estudo deste trabalho os erros médios percentuais absolutos da previsão de geração no complexo eólico de Cerro Chato foram de 18,42% do PDP da Usina, 15,97% do modelo ETA, 20,96% e 20,30% do modelo WRF com resolução espacial de 15 km desconsiderando e considerando a influência da variação da temperatura, respectivamente, e de 7,55% e 6,89% do modelo WRF com resolução espacial de 5 km desconsiderando e considerando a influência da variação da temperatura, respectivamente. Os erros médios percentuais absolutos das programações de geração de energia do complexo eólico de Osório foram de 16,29% do PDP da usina, 19,19% do modelo ETA, 9,38% e 8,78% do modelo WRF com resolução espacial de 15 km desconsiderando e considerando a influência da variação da temperatura, respectivamente, e de 5,94% e 5,09% do modelo WRF com resolução espacial de 5 km desconsiderando e considerando a influência da variação da temperatura, respectivamente. / The use of wind energy for electricity production has increased worldwide. According to the PDE 2022 (Ten Year Plan for Energy Expansion) provided by EPE (Energy Research Company) installed capacity of wind power stemmed in 2013 was 2,2 GW, about 1.8% of the Brazilian. The energy matrix, with perspective increase to 22.4 GW, which in 2023 represent about 11.8% of the Brazilian energy matrix. Thus the need to have a schedule of availability of power wind farms is extremely important in the operation of the Brazilian electrical system. Using the wind speed data generated by the WRF model with spatial resolution of 15 km and 5 km 100 m long made up an estimated power generation for wind complex of Cerro Chato and Osorio from 9 August 2014 to 29 August 2014. Then compared with the daily schedule of data for energy production made by plants, by ETA model and the actual generation of the same period, provided by the National System Operator in its weekly newsletters. During the study period of this study, the absolute percentage mean errors of prediction in wind generation complex of Cerro Chato were 18.42% of the Plant PDP, 15.97% of the ETA model, 20.96% and 20.30% of the WRF model with spatial resolution of 15 km disregarding and considering the influence of temperature variation, respectively, and 7.55% and 6.89% of the WRF model with spatial resolution of 5 km disregarding and considering the influence of temperature variation, respectively. The absolute percentage mean errors schedules of the wind farm of Osório power generation were 16.29% of the plant's PDP, 19.19% of the ETA model, 9.38% and 8.78% of the WRF model with spatial resolution 15 km disregarding and considering the influence of temperature variation, respectively, and 5.94% and 5.09% of the WRF model with spatial resolution of 5 km disregarding and considering the influence of temperature variation, respectively.

Este trabalho propõe um novo método de proteção de geradores síncronos baseado em inteligência artificial, mais especificamente lógica fuzzy, com o propósito de melhorar a proteção destes componentes vitais aos sistema elétricos de potência. Um sistema elétrico de potência completo composto por geradores, linhas de transmissão e cargas foi simulado através do Real Time Digital Simulator para fornecer dados para realização de testes e validação do algoritmo de proteção inteligente. Adicionalmente, foram desenvolvidos dois esquemas experimentais que proporcionaram a obtenção de um conjunto extensivo de ensaios de faltas internas em dois geradores síncronos reais, com o objetivo de fornecer dados para comprovar a eficácia da proteção proposta. Um sistema integrado de software e hardware cujo objetivo é servir de plataforma para desenvolver e executar em tempo real algoritmos de proteção aplicados foi desenvolvido. Esse sistema integrado foi utilizado nos testes embarcados em tempo-real do algoritmo de proteção desenvolvido. Apresenta-se também um arranjo composto por funções de proteção tradicionais mais utilizadas em campo, as quais serviram como base de comparação de desempenho para o esquema de proteção inteligente desenvolvido. Os resultados apresentados mostram que o método de proteção inteligente proposto é mais sensível para detectar instantaneamente faltas fase-terra em geradores síncronos com aterramento de alta-impedância, além de ser capaz de identificar faltas entre-espiras e entre-caminhos / This work presents the development of a synchronous generator protective technique based on artificial intelligence, specifically fuzzy logic, in order to improve the protection of these vital components of the electric power system. A complete electric power system composed of generators, transmission lines and loads was simulated using the Real Time Digital Simulator to provide data for testing and validating the intelligent protection algorithm. Additionally, an extensive set of internal fault experiments conducted on two actual synchronous generators provided oscillograms to demostrate the proposed protection effectiveness. An integrated hardware and software system whose purpose is to serve as a platform for developing and executing real-time protection algorithms is presented. This integrated system was used for real-time embedded testing of the protection algorithm developed. An arrangement composed of traditional protection functions most used in the field is also presented, this arrangement served as a comparison basis for the intelligent protection scheme performance. The results show that the intelligent protection is more sensitive to detect instantly ground faults in synchronous generators with high-impedance grounding, it is also shown that the proposed scheme is able to identify inter-turns and inter-circuits faults

This thesis is devoted to the development of new approaches for control coordination of PSSs (power system stabilisers) and FACTS (flexible alternating current transmission system) devices for achieving and enhancing small-disturbance stability in multi-machine power systems. The key objectives of the research reported in the thesis are, through optimal control coordination of PSSs and/or FACTS devices, those of maintaining satisfactory power oscillation damping and secure system operation when the power system is subject to persisting disturbances in the form of load demand fluctuations and switching control. Although occurring less frequently, fault disturbances are also considered in the assessment of the control coordination performance. Based on the constrained optimisation method in which the eigenvalue-based objective function is minimised to identify the optimal parameters of power system damping controllers, the thesis first develops a procedure for designing the control coordination of PSSs and FACTS devices controllers. The eigenvalue-eigenvector equations associated with the selected electromechanical modes form a set of equality constraints in the optimisation. The key advance of the procedure is that there is no need for any special software system for eigenvalue calculations, and the use of sparse Jacobian matrix for forming the eigenvalue-eigenvector equations leads to the sparsity formulation which is essential for large power systems. Inequality constraints include those for imposing bounds on the controller parameters. Constraints which guarantee that the modes are distinct ones are derived and incorporated in the control coordination formulation, using the property that eigenvectors associated with distinct modes are linearly independent. The robustness of the controllers is achieved very directly through extending the sets of equality constraints and inequality constraints in relation to selected eigenvalues and eigenvectors associated with the state matrices of power systems with loading conditions and/or network configurations different from that of the base case. On recognising that the fixed-parameter controllers, even when designed with optimal control coordination, have an inherent limitation which precludes optimal system damping for each and every possible system operating condition, the second part of ii the research has a focus on adaptive control techniques and their applications to power system controllers. In this context, the thesis reports the development of a new design procedure for online control coordination which leads to adaptive PSSs and/or supplementary damping controllers (SDCs) of FACTS devices for enhancing the stability of the electromechanical modes in a multi-machine power system. The controller parameters are adaptive to the changes in system operating condition and/or configuration. Central to the design is the use of a neural network synthesised to give in its output layer the optimal controller parameters adaptive to system operating condition and configuration. A novel feature of the neural adaptive controller is that of representing the system configuration by a reduced nodal impedance matrix which is input to the neural network.

Disturbances in the supply of electric power can have serious implications for everyday life as well as for national (homeland) security. A power outage can be initiated by natural disasters, adverse weather, technical failures, human errors, sabotage, terrorism, and acts of war. The vulnerability of a system is described as a sensitivity to threats and hazards, and is measured by P (Q(t) &gt; q), i.e. the probability of at least one disturbance with negative societal consequences Q larger than some critical value q, during a given period of time (0,t]. The aim of the thesis is to present methods for quantitative vulnerability analysis of electric power delivery networks to enable effective strategies for prevention, mitigation, response, and recovery to be developed. Paper I provides a framework for vulnerability assessment of infrastructure systems. The paper discusses concepts and perspectives for developing a methodology for vulnerability analysis, and gives examples related to power systems. Paper II analyzes the vulnerability of power delivery systems by means of statistical analysis of Swedish disturbance data. It is demonstrated that the size of large disturbances follows a power law, and that the occurrence of disturbances can be modeled as a Poisson process. Paper III models electric power delivery systems as graphs. Statistical measures for characterizing the structure of two empirical transmission systems are calculated, and a structural vulnerability analysis is performed, i.e. a study of the connectivity of the graph when vertices and edges are disabled. Paper IV discusses the origin of power laws in complex systems in terms of their structure and the dynamics of disturbance propagation. A branching process is used to model the structure of a power distribution system, and it is shown that the disturbance size in this analytical network model follows a power law. Paper V shows how the interaction between an antagonist and the defender of a power system can be modeled as a game. A numerical example is presented, and it is studied if there exists a dominant defense strategy, and if there is an optimal allocation of resources between protection of components, and recovery. / QC 20100831

Security analysis of a power system requires a process called contingency analysis that analyzes results from all possible single contingencies (i.e. outages) in the system. The process of contingency analysis requires the definition of a parameter that is used to monitor a certain aspect of the system, which is called a performance index. The performance index definitions used traditionally have been highly nonlinear, and the results have not accurately predicted the outcome of the performance index in some cases. These incorrect results are referred to as misrankings since the contingency results are usually placed in order of severity so that the most severe cases are evident. This thesis considers a new definition of contingency ranking using a more linearized definition of the performance index. The construction of both the new, proposed definition and the classic definition both consider the current loading of circuits in the system as compared to their rated values. Specifically, the parameter measured by the proposed definition measures the difference, while the more nonlinear definition uses a ratio of the two quantities, which is then raised to a higher power. A small, four bus test system is used to demonstrate the benefits of the new, more linearized definition. The average percent error for all single line contingencies of the system decreased by over 9.5% using the proposed definition as compared to the previous one. This decrease in error allows this performance index to monitor a similar parameter (comparing current loading and current rating of the lines) and achieve a higher degree of accuracy. Further linearization of this proposed definition also shows a reduction in the average percent error by an additional 22% so that when compared to the original, highly nonlinear definition, the average error is reduced by almost 30%. By linearizing the definition of the performance index, the results are more accurate and misrankings are less likely to occur from the security analysis process.