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The thesis reports the results of comprehensive studies carried out to explore the impact of midpoint FACTS Controllers (STATCOM and SVC) on the generator distance phase backup protection in order to identify important issues that protection engineers need to consider when designing and setting a generator protection system. In addition, practical, feasible and simple solutions to mitigate the adverse impact of midpoint FACTS Controllers on the generator distance phase backup protection are explored. The results of these studies show that midpoint FACTS Controllers have an adverse effect on the generator distance phase backup protection. This adverse effect, which can be in the form of underreach, overreach or a time delay, varies according to the fault type, fault location and generator loading. Moreover, it has been found that the adverse effect of the midpoint FACTS Controllers extends to affect the coordination between the generator distance phase backup protection and the generator steady-state overexcited capability limit. The Support Vector Machines classification technique is proposed as a replacement for the existing generator distance phase backup protection relay in order to alleviate potential problems. It has been demonstrated that this technique is a very promising solution, as it is fast, reliable and has a high performance efficiency. This will result in enhancing the coordination between the generator phase backup protection and the generator steady-state overexcited capability limit in the presence of midpoint FACTS Controllers. The thesis also presents the results of investigations carried out to explore the impact of the generator distance phase backup protection relay on the generator overexcitation thermal capability. The results of these investigations reveal that with the relay settings according to the current standards, the generator is over-protected and the generator distance phase backup protection relay restricts the generator overexcitation thermal capability during system disturbances. This restriction does not allow the supply of the maximum reactive power of the generating unit during such events. The restriction on the generator overexcitation thermal capability caused by the generator distance phase backup protection relay highlights the necessity to revise the relay settings. The proposed solution in this thesis is to reduce the generator distance phase backup protection relay reach in order to provide secure performance during system disturbances.

The thesis reports the results of comprehensive studies carried out to explore the impact of midpoint FACTS Controllers (STATCOM and SVC) on the generator distance phase backup protection in order to identify important issues that protection engineers need to consider when designing and setting a generator protection system. In addition, practical, feasible and simple solutions to mitigate the adverse impact of midpoint FACTS Controllers on the generator distance phase backup protection are explored. The results of these studies show that midpoint FACTS Controllers have an adverse effect on the generator distance phase backup protection. This adverse effect, which can be in the form of underreach, overreach or a time delay, varies according to the fault type, fault location and generator loading. Moreover, it has been found that the adverse effect of the midpoint FACTS Controllers extends to affect the coordination between the generator distance phase backup protection and the generator steady-state overexcited capability limit. The Support Vector Machines classification technique is proposed as a replacement for the existing generator distance phase backup protection relay in order to alleviate potential problems. It has been demonstrated that this technique is a very promising solution, as it is fast, reliable and has a high performance efficiency. This will result in enhancing the coordination between the generator phase backup protection and the generator steady-state overexcited capability limit in the presence of midpoint FACTS Controllers. The thesis also presents the results of investigations carried out to explore the impact of the generator distance phase backup protection relay on the generator overexcitation thermal capability. The results of these investigations reveal that with the relay settings according to the current standards, the generator is over-protected and the generator distance phase backup protection relay restricts the generator overexcitation thermal capability during system disturbances. This restriction does not allow the supply of the maximum reactive power of the generating unit during such events. The restriction on the generator overexcitation thermal capability caused by the generator distance phase backup protection relay highlights the necessity to revise the relay settings. The proposed solution in this thesis is to reduce the generator distance phase backup protection relay reach in order to provide secure performance during system disturbances.

Tecnologias HVDC que utilizam conversores do tipo fonte de tensão, o VSC-HVDC, ainda não são completamente difundidas e aplicadas no Brasil, em contraste com outros países que começaram a estudar e empregar este tipo de transmissão. Comparado com o HVDC tradicional, o VSC-HVDC é uma tecnologia de transmissão mais eficiente e pode superar deficiências encontradas na transmissão em corrente contínua convencional. O VSC-HVDC pode ser utilizado de maneira mais eficiente nas novas redes de energia, para alimentar ilhas, integração de geração eólica, renovação das linhas em centros urbanos, aplicações multiterminais e conexão com sistemas fracos. Por se tratar de uma tecnologia recente, o VSC-HVDC ainda não é amplamente adotado e uma das principais limitações da utilização destes sistemas é a sua fragilidade diante faltas na linha de corrente contínua. Neste contexto, limitadores de corrente de falta (LCF) podem ser utilizados para minimizar o impacto das faltas. A ação dos limitadores é benéfica ao sistema durante condições de falta, contudo, ainda assim é necessária a atuação do sistema de proteção para extinguir a condição faltosa. Portanto, este trabalho visa propor e avaliar um novo esquema de proteção que opere de maneira seletiva e confiável para sistemas VSC-HVDC na presença de LCF baseados em materiais supercondutores ou LCF indutivos. Para tanto, foram implementadas quatro funções de proteção tradicionais das linhas em CC, a saber: direcional de corrente, diferencial, sobrecorrente com restrição de tensão e ondas viajantes, e ainda, foi proposta uma nova função de proteção, a de condutância, a qual apresentou o menor tempo de identificação de falta, considerando as faltas mais severas. Adicionalmente, foi avaliado o comportamento destas funções quando o sistema apresenta os LCF em série com a linha. Foi demonstrado que é possível extrair os benefícios dos LCF sem deteriorar a qualidade dos resultados das funções de proteção, o que aumenta a segurança e confiabilidade dos sistemas VSC-HVDC, uma vez que os impactos das faltas são minimizados e as mesmas são identificadas em um curto intervalo de tempo. / HVDC technology based on voltage source converters, VSC-HVDC, are not yet fully disseminated and applied in Brazil, in contrast to other countries that have begun to study and widely employ this type of transmission technology. When compared with traditional HVDC systems, VSC-HVDC systems are more efficient and can overcome the challenges encountered in the conventional direct current transmission. The VSC-HVDC can be used more efficiently in the new energy networks to feed islands, integration of wind generation, renewal of lines in urban centers, multiterminal applications and connection with weak systems. Because it is a recent technology, VSC-HVDC is not yet widely adopted and a major limitation of using these systems is their weakness against faults in the DC line. In this context, fault current limiters (FCL) can be used to minimize the impact of faults. The action of the limiters is beneficial to the system during fault conditions, however, the use of protection schemes to detect the fault and extinguish the faulty condition is still required. Therefore, this work aims to propose and evaluate a new protection scheme operating in selective and reliable way for VSC-HVDC systems in the presence of FCL based in superconductor materials or inductive FCL. To reach such a goal, in this work it has been implemented four traditional DC lines protection functions, namely: directional current, differential, overcurrent with voltage restraint and traveling waves, and also proposed a new protection function, which is based on the conductance. This last protection function has presented the lowest detection time, when considering the most severe faults. In addition, it was evaluated the behavior of these functions when the system presents the FCL in series with the DC line. It has been shown that it is possible to extract the benefits of FCL without deteriorating the quality of the results of the protection functions, which increases the safety and reliability of the VSC-HVDC systems, since the impact of faults is minimized and they are identified in a short time.

Tecnologias HVDC que utilizam conversores do tipo fonte de tensão, o VSC-HVDC, ainda não são completamente difundidas e aplicadas no Brasil, em contraste com outros países que começaram a estudar e empregar este tipo de transmissão. Comparado com o HVDC tradicional, o VSC-HVDC é uma tecnologia de transmissão mais eficiente e pode superar deficiências encontradas na transmissão em corrente contínua convencional. O VSC-HVDC pode ser utilizado de maneira mais eficiente nas novas redes de energia, para alimentar ilhas, integração de geração eólica, renovação das linhas em centros urbanos, aplicações multiterminais e conexão com sistemas fracos. Por se tratar de uma tecnologia recente, o VSC-HVDC ainda não é amplamente adotado e uma das principais limitações da utilização destes sistemas é a sua fragilidade diante faltas na linha de corrente contínua. Neste contexto, limitadores de corrente de falta (LCF) podem ser utilizados para minimizar o impacto das faltas. A ação dos limitadores é benéfica ao sistema durante condições de falta, contudo, ainda assim é necessária a atuação do sistema de proteção para extinguir a condição faltosa. Portanto, este trabalho visa propor e avaliar um novo esquema de proteção que opere de maneira seletiva e confiável para sistemas VSC-HVDC na presença de LCF baseados em materiais supercondutores ou LCF indutivos. Para tanto, foram implementadas quatro funções de proteção tradicionais das linhas em CC, a saber: direcional de corrente, diferencial, sobrecorrente com restrição de tensão e ondas viajantes, e ainda, foi proposta uma nova função de proteção, a de condutância, a qual apresentou o menor tempo de identificação de falta, considerando as faltas mais severas. Adicionalmente, foi avaliado o comportamento destas funções quando o sistema apresenta os LCF em série com a linha. Foi demonstrado que é possível extrair os benefícios dos LCF sem deteriorar a qualidade dos resultados das funções de proteção, o que aumenta a segurança e confiabilidade dos sistemas VSC-HVDC, uma vez que os impactos das faltas são minimizados e as mesmas são identificadas em um curto intervalo de tempo. / HVDC technology based on voltage source converters, VSC-HVDC, are not yet fully disseminated and applied in Brazil, in contrast to other countries that have begun to study and widely employ this type of transmission technology. When compared with traditional HVDC systems, VSC-HVDC systems are more efficient and can overcome the challenges encountered in the conventional direct current transmission. The VSC-HVDC can be used more efficiently in the new energy networks to feed islands, integration of wind generation, renewal of lines in urban centers, multiterminal applications and connection with weak systems. Because it is a recent technology, VSC-HVDC is not yet widely adopted and a major limitation of using these systems is their weakness against faults in the DC line. In this context, fault current limiters (FCL) can be used to minimize the impact of faults. The action of the limiters is beneficial to the system during fault conditions, however, the use of protection schemes to detect the fault and extinguish the faulty condition is still required. Therefore, this work aims to propose and evaluate a new protection scheme operating in selective and reliable way for VSC-HVDC systems in the presence of FCL based in superconductor materials or inductive FCL. To reach such a goal, in this work it has been implemented four traditional DC lines protection functions, namely: directional current, differential, overcurrent with voltage restraint and traveling waves, and also proposed a new protection function, which is based on the conductance. This last protection function has presented the lowest detection time, when considering the most severe faults. In addition, it was evaluated the behavior of these functions when the system presents the FCL in series with the DC line. It has been shown that it is possible to extract the benefits of FCL without deteriorating the quality of the results of the protection functions, which increases the safety and reliability of the VSC-HVDC systems, since the impact of faults is minimized and they are identified in a short time.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-09-21T15:12:21Z No. of bitstreams: 1 Thiago Guimarães Tavares_.pdf: 1283558 bytes, checksum: b458af354b61f6414921f26690f0c06f (MD5) / Made available in DSpace on 2016-09-21T15:12:21Z (GMT). No. of bitstreams: 1 Thiago Guimarães Tavares_.pdf: 1283558 bytes, checksum: b458af354b61f6414921f26690f0c06f (MD5) Previous issue date: 2016-07-22 / Nenhuma / O objetivo do trabalho é a compreensão sobre como os aspectos técnicos, regulatórios e econômicos impactam na cadeia produtiva da piscicultura no Sudeste do Tocantins. O consumo de pescado tem aumentado gradativamente, considerando-se tanto a demanda mundial, quanto a do mercado brasileiro. A causa desse aumento de consumo, pode ser resumida pelo aumento da população e pela necessidade de se consumir alimentos mais saudáveis e nutritivos, como o peixe. O Estado do Tocantins tem apresentado um grande crescimento na cadeia produtiva da piscicultura, e o sudeste do Estado é responsável por mais da metade dessa produção. Esse crescimento tem impactado positivamente em vários setores gerando emprego e arrecadação. Apesar de um notável desenvolvimento do setor nos últimos anos, encontra-se na literatura relatos de que limitadores devem ser transpostos para que a cadeia se estabeleça de forma sustentável. Dentre as lacunas apresentadas estão as relativas aos aspectos técnicos, regulatórios e econômicos, consideradas como os maiores entraves de crescimento da cadeia da piscicultura. Para o desenvolvimento do trabalho utiliza-se como metodologia a aplicação de um estudo de caso que se desenvolve através de entrevistas com diversos elos importantes da cadeia. Busca-se, após a caracterização da cadeia compreender como os aspectos estão impactando a cadeia no Sudeste do Estado. / The objective is the understanding of how the technical, regulatory and economic aspects impact the productive chain of fish farming in Southeastern Tocantins. The fish consumption has gradually increased, considering both global demand, and the Brazilian market. The cause of this increase in consumption can be summed up by the increase in population and the need to consume more healthy and nutritious foods, such as fish. The State of Tocantins has shown strong growth in the productive chain of fish, and the southeast of the State is responsible for more than half of this production. This growth has impacted positively in various sectors generating jobs and revenue. Despite a remarkable development of the sector in recent years, it is reported in the literature that constraints must be tackled so that the chain is established sustainably. Among the gaps presented are those relating to technical, regulatory and economic, regarded as the biggest barriers to the growth of the fish chain. In this context, this study establishes the theme of the production chain in Southeastern Tocantins fish. For the development work is used as a methodology to apply a case study that is developed through interviews with several important links in the chain. After that impact the chain in the Southeastern State are described and characterized.

<p>The MUSCL-Hancock finite volume method with different slope limiters has been analyzed in the context of a fast transient flow problem. A derivation and analysis of the axial forces inside a pipe system due to a flow transient is also performed. </p><p>The following slope limiters were implemented and compared: MC, van Leer, van Albada, Minmod and Superbee. The comparison was based on the method's ability to calculate the forces due to a flow transient inside a pipe system.</p><p>The tests and comparisons in this thesis show that the MC, van Leer, van Albada and Minmod limiters behave very much the same for the flow transient problem. If one would rank these four limiters with respect to the numerical error, the order would be the one presented above, the MC limiter being the most accurate. The error the four limiters produce is mainly of diffusive nature and it is just the magnitude of the diffusion that seems to differ between the methods. One should also note that the workload rank of the four limiters is the same as the order presented above. The MC limiter being the least efficient of the four and the Minmod limiter the most efficient.</p><p>In most of the tests performed the Superbee limiter display a rather negative unpredictable behavior. For some relatively simple cases this particular approach shows big difficulties maintaining the dynamical properties of the force. However, the upside of the Superbee limiter is its remarkable ability to maintain the maximum value of the forces present in the pipe system, preventing underestimation of the maximum magnitude of the force.</p>

The MUSCL-Hancock finite volume method with different slope limiters has been analyzed in the context of a fast transient flow problem. A derivation and analysis of the axial forces inside a pipe system due to a flow transient is also performed.  The following slope limiters were implemented and compared: MC, van Leer, van Albada, Minmod and Superbee. The comparison was based on the method's ability to calculate the forces due to a flow transient inside a pipe system. The tests and comparisons in this thesis show that the MC, van Leer, van Albada and Minmod limiters behave very much the same for the flow transient problem. If one would rank these four limiters with respect to the numerical error, the order would be the one presented above, the MC limiter being the most accurate. The error the four limiters produce is mainly of diffusive nature and it is just the magnitude of the diffusion that seems to differ between the methods. One should also note that the workload rank of the four limiters is the same as the order presented above. The MC limiter being the least efficient of the four and the Minmod limiter the most efficient. In most of the tests performed the Superbee limiter display a rather negative unpredictable behavior. For some relatively simple cases this particular approach shows big difficulties maintaining the dynamical properties of the force. However, the upside of the Superbee limiter is its remarkable ability to maintain the maximum value of the forces present in the pipe system, preventing underestimation of the maximum magnitude of the force.

For effective operation of microgrid systems (MGSs), it is important to understand the major types of power grid failures and how to deal with them. Detecting the fault, locating it, and isolating the faulty line are important to avoid damaging components and interrupting the service for customers. This will also improve the reliability and protection level of the system during fault conditions. Among the most successful protection methods to limit fault currents in power systems is the fault current limiter (FCL). The FCL improves the reliability of the system, voltage stability, and the fault current reduction. However, limited researches consider its applications inMGSs. The location and impedance size of the FCL play a major role in limiting fault currents in the system. Several studies concluded that installing FCLs near all generators, transformers, or loads in the system enhanced the performance of the system during fault conditions. However, increasing the number of FCLs in the system leads to an increase in cost. This dissertation proposes several effective approaches to specify the optimal locations and impedance values of the required number of installed FCLs in a grid-connected MGS. These FCLs improve the reliability and the protection level of the system by limiting fault currents during fault conditions. The goal is to reduce the required number of installed FCLs in the system. These installed FCLs must be able to reduce fault currents under the interrupting ratings of circuit breakers in the system. This goal will lead to lower the cost of installed protection devices in the system. In order to achieve this goal, this dissertation presents a novel fault management approach, sensitivity analysis, and an optimization model to find the optimal solutions. The study of this dissertation is meant to be used during the planning stage of power distribution system design. The results of this dissertation prove the robustness of the proposed approaches. This enhances the system’s performance while minimizing the required number of installed FCLs. Their sizes limit fault currents within safe ranges. Thus, the FCL significantly improves the reliability and protection scheme of the grid-connected MGS.