Numerical relays are the result of the application of microprocessor technology in relay industry. Numerical relays have the ability to communicate with its peers, are economical and are easy to operate, adjust and repair. Modeling of digital and numerical relays is important to adjust and settle protection equipment in electrical facilities and to train protection personnel. Designing of numerical relays is employed to produce new prototypes and protection algorithms. Computer models of numerical relays for the study of protection systems are greatly enhanced when working along with an electromagnetic transient program (emtp). A literature survey has revealed that previous modeling techniques presented a lack of automation in the generation of relay models, or show high complexity in linking the numerical relay models with the power system modeled in the emtp. <p> This thesis describes a new approach of modeling and designing of numerical relays. The proposed methodology employs a Visual C++-based program (PLSA) to obtain from the user the specifications of the relay to be designed, and to process this information to generate the FORTRAN code that represents the functional blocks of the relay. This generated code is incorporated in a PSCAD/EMTDC case using a resource called component, which facilitates the creation of user-custom models in PSCAD/EMTDC. Convenient electrical and logical signals are connected to the inputs and outputs of the PSCAD/EMTDC component. Further additions of digital relay models into the PSCAD/EMTDC case constitute the protection system model. The thesis describes a procedure for designing distance and differential relay models, but the methodology may be extended to design models of other relay elements. <p> A number of protection system studies were performed with the structure created with the proposed methodology. Adjustment of distance and differential relays were studied. Relay performance under CT saturation and the effects of the removal of anti-aliasing analog filter were investigated. Local and remote backup distance protection of transmission lines was simulated. The adjustment of differential protection of power transformer to overcome the effects of inrush current was performed. Power transformer differential protection responses to internal and external faults were considered. <p>Additionally, a set of tests were performed to investigate the consistency of the relay models generated with the proposed methodology. The results showed that the numerical relay models respond satisfactorily according with the expected results of the tests.

Numerical relays are the result of the application of microprocessor technology in relay industry. Numerical relays have the ability to communicate with its peers, are economical and are easy to operate, adjust and repair. Modeling of digital and numerical relays is important to adjust and settle protection equipment in electrical facilities and to train protection personnel. Designing of numerical relays is employed to produce new prototypes and protection algorithms. Computer models of numerical relays for the study of protection systems are greatly enhanced when working along with an electromagnetic transient program (emtp). A literature survey has revealed that previous modeling techniques presented a lack of automation in the generation of relay models, or show high complexity in linking the numerical relay models with the power system modeled in the emtp. <p> This thesis describes a new approach of modeling and designing of numerical relays. The proposed methodology employs a Visual C++-based program (PLSA) to obtain from the user the specifications of the relay to be designed, and to process this information to generate the FORTRAN code that represents the functional blocks of the relay. This generated code is incorporated in a PSCAD/EMTDC case using a resource called component, which facilitates the creation of user-custom models in PSCAD/EMTDC. Convenient electrical and logical signals are connected to the inputs and outputs of the PSCAD/EMTDC component. Further additions of digital relay models into the PSCAD/EMTDC case constitute the protection system model. The thesis describes a procedure for designing distance and differential relay models, but the methodology may be extended to design models of other relay elements. <p> A number of protection system studies were performed with the structure created with the proposed methodology. Adjustment of distance and differential relays were studied. Relay performance under CT saturation and the effects of the removal of anti-aliasing analog filter were investigated. Local and remote backup distance protection of transmission lines was simulated. The adjustment of differential protection of power transformer to overcome the effects of inrush current was performed. Power transformer differential protection responses to internal and external faults were considered. <p>Additionally, a set of tests were performed to investigate the consistency of the relay models generated with the proposed methodology. The results showed that the numerical relay models respond satisfactorily according with the expected results of the tests.

This thesis presents a new way of combining non-linear optimization algorithms and electromagnetic transient (EMT) simulation. In this new combination, a non-linear optimization algorithm utilizes a real-time EMT simulation environment as objective function evaluator. However, as more applications of the off-line EMT simulation software implementation were made, the combination between non-linear optimization algorithms and off-line EMT simulation software revealed new need, which this research work attempts to address. The first need arose from the speed of simulation of the off-line EMT simulation software. With a certain breed of non-linear optimization algorithms, heuristics bases algorithms in particular, a large number of objective function evaluations are required before the termination or convergence criterion in the selected algorithms is satisfied. Sometimes, the number of evaluations as well as the complexity of the simulation case where the objective function is based upon translates into a very long simulation time, which goes beyond the boundary of given resources. This research work attempts to address this simulation timing issue by capitalizing on the real timeness of the simulation environment as well as utilizing the multiple instances of the simulation environment in parallel. The second need arose from the modeling requirement of the off-line EMT simulation software. In order to properly design the necessary objective function evaluator, which is largely a simulation case, a large amount of information needs to be embedded into the case. Under certain circumstances, the necessary information would not be available. Therefore, the simulation case needs to include approximations which may cause compromise in the end result. This limitation becomes more obvious when a real world device such as a commercial controller becomes involved. On the contrary, this limitation can be addressed by the real-time simulation environment because this environment can be directly interfaced with the real world device. In this way, the need for detailed information regarding the device is eliminated. This elimination would enlarge the application of the combination, between the non-linear optimization algorithm and EMT type simulation environment. The effectiveness of the proposed approach is demonstrated by various examples throughout this thesis.

This thesis presents a new way of combining non-linear optimization algorithms and electromagnetic transient (EMT) simulation. In this new combination, a non-linear optimization algorithm utilizes a real-time EMT simulation environment as objective function evaluator. However, as more applications of the off-line EMT simulation software implementation were made, the combination between non-linear optimization algorithms and off-line EMT simulation software revealed new need, which this research work attempts to address. The first need arose from the speed of simulation of the off-line EMT simulation software. With a certain breed of non-linear optimization algorithms, heuristics bases algorithms in particular, a large number of objective function evaluations are required before the termination or convergence criterion in the selected algorithms is satisfied. Sometimes, the number of evaluations as well as the complexity of the simulation case where the objective function is based upon translates into a very long simulation time, which goes beyond the boundary of given resources. This research work attempts to address this simulation timing issue by capitalizing on the real timeness of the simulation environment as well as utilizing the multiple instances of the simulation environment in parallel. The second need arose from the modeling requirement of the off-line EMT simulation software. In order to properly design the necessary objective function evaluator, which is largely a simulation case, a large amount of information needs to be embedded into the case. Under certain circumstances, the necessary information would not be available. Therefore, the simulation case needs to include approximations which may cause compromise in the end result. This limitation becomes more obvious when a real world device such as a commercial controller becomes involved. On the contrary, this limitation can be addressed by the real-time simulation environment because this environment can be directly interfaced with the real world device. In this way, the need for detailed information regarding the device is eliminated. This elimination would enlarge the application of the combination, between the non-linear optimization algorithm and EMT type simulation environment. The effectiveness of the proposed approach is demonstrated by various examples throughout this thesis.

Apesar do grande interesse no comportamento dinâmico das cargas, existe uma lacuna em investigações considerando o seu desempenho transitório, quando alimentadas por linhas de transmissão e a rejeição de carga ocorre com a abertura dos disjuntores do lado fonte, causando sobretensões temporárias. Este trabalho analisa as sobretensões temporárias causadas por este evento em uma carga de grande porte, constituída por motores síncronos e assíncronos, que pode operar parte do tempo somente com motores assíncronos. Para tanto, foi desenvolvido um modelo de motor de indução, segundo uma trnsformaçãoos eixos direto e de quadratura, com a finalidade de validar e efetuar comparações com o modelo existente no programa ATP. Dos vários testes de validação realizados e de posse de modelos confiáveis de máquinas, principalmente para os motores de indução, foram examinadas diversas situações operativas, com o programa ATP, procurando investigar as solicitações dielétricas em equipamentos e sobre-excitação de transformadores, quando a linha de transmissão opera com e sem compensação reativa. Dessa análise pode-se obter um panorama do risco operativo em diferentes cenários, verificando-se a necessidade de compensação reativa da linha. / In spite of the great interest in the dynamic behavior of loads, there is a gap in investigations considering their transient performance, when they are fed by transmission lines and a load rejection occurs with the tripping of the breakers of the source side, causing temporary overvoltages. This paper analyzes the temporary overvoltages caused by this event in a large load, constituted by synchronous and asynchronous motors, that can operate part of the time only with asynchronous motors. Therefore, a model of induction motor was developed, according to the direct and quadrature axes transformation, with the purpose to validate and make comparisons with the existent model in the ATP program. From several validation tests and using reliable machine models, mainly for the induction motors, some operative conditions were examined with the ATP program, trying to investigate equipment dielectric stresses and over-excitation of transformers, when the transmission line operates with and without reactive compensation. From this analysis it can be obtained an overview of the operative risk in different sceneries, being verified the need of reactivate compensation of the line.

Apesar do grande interesse no comportamento dinâmico das cargas, existe uma lacuna em investigações considerando o seu desempenho transitório, quando alimentadas por linhas de transmissão e a rejeição de carga ocorre com a abertura dos disjuntores do lado fonte, causando sobretensões temporárias. Este trabalho analisa as sobretensões temporárias causadas por este evento em uma carga de grande porte, constituída por motores síncronos e assíncronos, que pode operar parte do tempo somente com motores assíncronos. Para tanto, foi desenvolvido um modelo de motor de indução, segundo uma trnsformaçãoos eixos direto e de quadratura, com a finalidade de validar e efetuar comparações com o modelo existente no programa ATP. Dos vários testes de validação realizados e de posse de modelos confiáveis de máquinas, principalmente para os motores de indução, foram examinadas diversas situações operativas, com o programa ATP, procurando investigar as solicitações dielétricas em equipamentos e sobre-excitação de transformadores, quando a linha de transmissão opera com e sem compensação reativa. Dessa análise pode-se obter um panorama do risco operativo em diferentes cenários, verificando-se a necessidade de compensação reativa da linha. / In spite of the great interest in the dynamic behavior of loads, there is a gap in investigations considering their transient performance, when they are fed by transmission lines and a load rejection occurs with the tripping of the breakers of the source side, causing temporary overvoltages. This paper analyzes the temporary overvoltages caused by this event in a large load, constituted by synchronous and asynchronous motors, that can operate part of the time only with asynchronous motors. Therefore, a model of induction motor was developed, according to the direct and quadrature axes transformation, with the purpose to validate and make comparisons with the existent model in the ATP program. From several validation tests and using reliable machine models, mainly for the induction motors, some operative conditions were examined with the ATP program, trying to investigate equipment dielectric stresses and over-excitation of transformers, when the transmission line operates with and without reactive compensation. From this analysis it can be obtained an overview of the operative risk in different sceneries, being verified the need of reactivate compensation of the line.

Orientador: Sérgio Kurokawa / Banca: Luiz Fernando Bovolato / Banca: Afonso José do Prado / Resumo: Esta dissertação descreve um processo alternativo para decompor uma linha de transmissão trifásica, simétrica e não transposta nos seus modos exatos por meio da utilização de duas matrizes de transformação. A primeira é a matriz de Clarke que desacopla a linha em suas componentes a, ß e zero. A componente ß é um modo exato enquanto que as componentes a e zero são acopladas. Em seguida, as componentes a e zero são representadas por uma linha bifásica que pode ser decomposta em seus modos exatos por meio de uma matriz de transformação adequada, cujos elementos podem ser sintetizados, no domínio do tempo, por técnicas de aproximações por curvas. O método pretende unir as vantagens da matriz de transformação exata (que produz modos exatos) com as vantagens da matriz de Clarke, que é real, independente da freqüência e facilmente representável em programas que realizam simulações de transitórios, como é o caso do EMTP. Assim, o método pode ser utilizado em situações em que o acoplamento entre as componentes a e zero não possa ser desconsiderado. O processo foi utilizado para simular a energização de uma linha trifásica, sem transposição, com um plano de simetria vertical, 440 kV e comprimento de 500 km que foi representada no domínio modal por meio do método proposto e também por meio do uso da matriz de autovetores (como sendo a matriz de decomposição modal). O método é coerente, pois foram obtidos resultados semelhantes com os dois métodos de decomposição modal, enquanto que com o uso somente da matriz de Clarke, verificou- se certa diferença em relação aos valores esperados. / Abstract: This dissertation describes an alternative procedure to decompose a non-transposed threephase transmission line into exact modes, by using two transformation matrices. The first one is Clarke's matrix, which separates the line into quasi-modes a, ß e zero. The ß component is an exact mode while a and zero are coupled. After that, the coupled components are represented by using a two-phase transmission line without a vertical symmetry plane that can be decomposed with a modal transformation matrix whose elements can be achieved, in timedomain, through standard curve-fitting techniques. The method intends to join the Clarke's matrix advantages which crucial aspect is being real, frequency-independent and easily represented in computational transient programs (EMTP) with eigenvector's matrix used in situations where the coupling between a and zero components cannot be disconsidered. The process was used to energize a three-phase transmission line with a vertical symmetry plane, which nominal voltage is 440kV and its length, 500km. It was represented in the modal domain by considered method and, on the other hand, by using eigenvector's matrix (as being the decomposition matrix). In fact, the obtained results had shown that the method is coherent, because it is obtained similar results with the application of the two mentioned modal decomposition methods, whereas with the use of Clarke's matrix, a perceptible difference in relation to the expected values was verified. / Mestre

The thesis introduces an approach for obtaining higher level decision support information using electromagnetic transient (EMT) simulation programs. In this approach, a suite of higher level driver programs (decision support tools) control the simulator to gain important information about the system being simulated. These tools conduct a sequence of simulation runs, in each of which the study parameters are carefully selected based on the observations of the earlier runs in the sequence. In this research two such tools have been developed in conjunction with the PSCAD/EMTDC electromagnetic transient simulation program. The first tool is an improved optimization algorithm, which is used for automatic optimization of the system parameters to achieve a desired performance. This algorithm improves the capabilities of the previously reported method of optimization-enabled electromagnetic transient simulation by using an enhanced gradient-based optimization algorithm with constraint handling techniques. In addition to allow handling of design problems with more than one objective the thesis proposes to augment the optimization tool with the technique of Pareto optimality. A sequence of optimization runs are conducted to obtain the Pareto frontier, which quantifies the tradeoffs between the design objectives. The frontier can be used by the designer for decision making process. The second tool developed in this research helps the designer to study the effects of uncertainties in a design. By using a similar multiple-run approach this sensitivity analysis tool provides surrogate models of the system, which are simple mathematical functions that represent different aspects of the system performance. These models allow the designer to analyze the effects of uncertainties on system performance without having to conduct any further time-consuming EMT simulations. In this research it has been also proposed to add probabilistic analysis capabilities to the developed sensitivity analysis tool. Since probabilistic analysis of a system using conventional techniques (e.g. Monte-Carlo simulations) normally requires a large number of EMT simulation runs, using surrogate models instead of the actual simulation runs yields significant savings in terms of shortened simulation time. A number of examples have been used throughout the thesis to demonstrate the application and usefulness of the proposed tools.

Natural lightning strikes induce impulsive overvoltages on transmission lines and its terminal equipment. These overvoltages may cause failures in insulation mechanisms of electrical devices in the power system. It is important to test the insulation strength of a device against these impulsive overvoltages. Usually, Marx generators are used to generate impulse waveforms for testing purposes. A novel approach is proposed to obtain resistor settings of a Marx generator for impulse testing of power transformers. This approach enables us to overcome most of the major challenges in the commonly used trial-and-error method, including excessive time consumption and potential damage to the transformer. The proposed approach uses the frequency response of the transformer to synthesize a circuit model. Then, a genetic algorithm based optimization-enabled electromagnetic transient simulation approach is used to obtain the resistor settings. The proposed approach is validated by a real impulse test conducted on a three phase power transformer.

The thesis introduces an approach for obtaining higher level decision support information using electromagnetic transient (EMT) simulation programs. In this approach, a suite of higher level driver programs (decision support tools) control the simulator to gain important information about the system being simulated. These tools conduct a sequence of simulation runs, in each of which the study parameters are carefully selected based on the observations of the earlier runs in the sequence. In this research two such tools have been developed in conjunction with the PSCAD/EMTDC electromagnetic transient simulation program. The first tool is an improved optimization algorithm, which is used for automatic optimization of the system parameters to achieve a desired performance. This algorithm improves the capabilities of the previously reported method of optimization-enabled electromagnetic transient simulation by using an enhanced gradient-based optimization algorithm with constraint handling techniques. In addition to allow handling of design problems with more than one objective the thesis proposes to augment the optimization tool with the technique of Pareto optimality. A sequence of optimization runs are conducted to obtain the Pareto frontier, which quantifies the tradeoffs between the design objectives. The frontier can be used by the designer for decision making process. The second tool developed in this research helps the designer to study the effects of uncertainties in a design. By using a similar multiple-run approach this sensitivity analysis tool provides surrogate models of the system, which are simple mathematical functions that represent different aspects of the system performance. These models allow the designer to analyze the effects of uncertainties on system performance without having to conduct any further time-consuming EMT simulations. In this research it has been also proposed to add probabilistic analysis capabilities to the developed sensitivity analysis tool. Since probabilistic analysis of a system using conventional techniques (e.g. Monte-Carlo simulations) normally requires a large number of EMT simulation runs, using surrogate models instead of the actual simulation runs yields significant savings in terms of shortened simulation time. A number of examples have been used throughout the thesis to demonstrate the application and usefulness of the proposed tools.