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

Atualmente, os avanços tecnológicos, especialmente dos recursos computacionais, possibilitam a realização de cálculos cada vez mais complexos. Em função destes avanços, transitórios hidráulicos antes desprezados ou estimados de forma rudimentar já podem ser calculados, especialmente nos casos em que o comportamento dos transitórios é crítico. Assim, torna-se necessário o desenvolvimento de métodos de cálculo que permitam prever quantitativamente tais transitórios uma vez que não há solução analítica para este problema. Neste trabalho são estudadas as condições de contorno para a utilização do modelo rígido de coluna líquida e sua respectiva solução numérica para o cálculo de transitórios durante o enchimento de uma tabulação com ramificação. Os modelos matemáticos foram testados em laboratório sob diversas condições, comprovando a viabilidade da utilização das ferramentas teóricas e numéricas desenvolvidas. / Nowadays there have been many technological advances, especially related to computational resources, that make possible more complex and huge calculations. Due to these advances, the evaluation of hydraulics transients, which have been disregarded or roughly estimated, is allowed to be more precisely performed especially when transient phenomena have significant importance. Then, the development of calculating methods that evaluates these transients effects becomes necessary once the analitic solution to these problems does not exist. This work presents the study of the boundary conditions of the rigid model applied to the fluid column and its numeral solution in order to calculate the transient behavior during filling of pipeline with ramifications. The results of mathematical models were compared with those from laboratory experiments under several conditions proving the feasibility of theoretical and numeral models.

This thesis is based on research made by the intermediate Palomar Transient Factory [(i)PTF]. The focus is on stripped-envelope (SE) supernovae (SNe) discovered by (i)PTF, and it is closely tied to the research on the SE SN iPTF13bvn, that occurred in the nearby galaxy NGC 5806. This SN was initially thought to have been the explosion of a very massive Wolf-Rayet star, but we have shown that this is very likely not the case. We suggest instead that iPTF13bvn originated from a binary system where the envelope was stripped off from the SN progenitor by tidal forces from a companion (Paper I). PTF12os exploded in the same galaxy as iPTF13bvn, and our analysis shows that PTF12os and  iPTF13bvn were very similar, and that both were also remarkably similar to the Type IIb SN 2011dh, in terms of their light-curves and spectra. In Paper II, hydrodynamical models were used to constrain the explosion parameters of iPTF13bvn, PTF12os and SN 2011dh; finding 56Ni masses in the range 0.063-0.075 solar masses (Ms), ejecta masses in the range 1.85-1.91 Ms, and kinetic energies in the range 0.54-0.94 x 1051 erg. Furthermore, using nebular models and late-time spectroscopy we were able to constrain the Zero-Age Main Sequence (ZAMS) mass to ~ 12 Ms, for iPTF13bvn and ≤ 15 Ms for PTF12os. In current stellar evolution models, stars with these masses on the ZAMS cannot lose their envelopes and become SE SNe without binary interactions. In Paper III we investigate a peculiar SE SN, iPTF15dtg; this SN lacks both hydrogen and helium and shows a double-peaked LC with a broad main LC peak. Using hydrodynamical modeling we show that iPTF15dtg had a very large ejecta mass (~ 10 Ms), resulting from an explosion of a very massive star (~ 35 Ms). The initial peak in the LC can be explained by the presence of extended material around the star, likely due to an episode of strong mass-loss experienced by the progenitor prior to the explosion. In Paper IV we perform a statistical study of the spectra of all 176 SE SNe (Type IIb, Ib and Ic) discovered by (i)PTF. The spectra of Type Ic SNe show O absorption features that are both stronger and broader (indicating faster expansion velocities) compared to Type IIb and Type Ib SNe. These findings along with very weak He absorption support the traditional picture with Type Ic SNe being heavily stripped of their He envelopes prior to the explosions, and argue against alternative explanations, such as differences in explosive mixing of 56Ni among the SE SN subtypes. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

Transient stability analysis is an important part of power planning and operation. For large power systems, such analysis is very time consuming and expensive. Therefore, an online transient stability assessment will be required as these large power systems are operated close to their maximum limits. In this thesis swallowtail catastrophe is used to determine the transient stability regions. The bifurcation set represents the transient stability region in terms of power system transient parameters bounded by the transient stability limits. The system modelling is generalized in such, that the analysis could handle either one or any number of critical machines. This generalized model is then tested on a three-machine as well as a seven-machine system. The results of the stability analysis done with the generalized method is compared with the time solution and the results were satisfactory. The transient stability regions determined are valid for any changes in loading conditions and fault location. This method is a good candidate for on-line assessment of transient stability of power systems. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This work demonstrates the use of digital simulation for analyzing protection system performance. For studies of complex, multi-relay protection systems, digital simulation provides utility engineers with an attractive alternative to relay testing techniques. The cost of digital simulation facilities can be lower than the cost of comparable testing facilities; relay hardware does not have to be made available for the test laboratory. Digital simulation would ordinarily be impractical for security and dependability studies, due to the thousands of individual simulations involved. The number of simulations needed can be greatly reduced by using a technique called "numerical logic replacement" for implementing the protection scheme logic. This unconventional technique makes near-misoperation visible from individual simulations. The likelihood of overlooking potential misoperation is thus much lower than with the usual direct (Boolean) implementations. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Orientador: Edevar Luvizotto Jr / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil / Made available in DSpace on 2018-07-31T23:13:39Z (GMT). No. of bitstreams: 1 Viaro_VivienLuciane_M.pdf: 4505576 bytes, checksum: 18be75ce76921d4bee282a5330042a53 (MD5) Previous issue date: 2001 / Resumo: O transiente hidráulico é definido como a transição entre duas condições de escoamento permanente. Nessa transição a variação das grandezas associadas ao escoamento, principalmente a pressão, é importante no dimensionamento e exploração da instalação hidráulica. Os estudos das situações transitórias e das manobras que as provocaram, são fundamentais para se garantir a segurança operacional das instalações hidráulicas em geral. A análise do escoamento transitório em condutos forcados é feita com base nas equações da continuidade e da quantidade de movimento. Uma das imprecisões associadas à mo delação convencional está no uso de uma formulação quase-estática para o termo de atrito, a qual é válida somente para escoamento permanente. Este trabalho faz uma comparação entre os resultados obtidos em modelo fisico e os da modelação matemática, considerando ou não uma modelação especial para o termo de atrito transitório. Foram utilizados os modelos propostos por Brunone et. al. (1991) e Vardy et. al. (1993), na descrição do termo de atrito variável / Abstract: Hydraulic transient is defined as the transition between two permanent flowing conditions. In this transition, the greatness variation related to the flowing, mainly the pressure, is important to the measuring and exploration of hydraulic installation. Studies about transitory situations and the shuntings that caused them are fundamental to guarantee operational safety of the hydraulic plants in general. The transitory flowing analysis in forced conduits is based on equations of continuity and on the amount of movement. One of the imprecisions related to the conventional modeling is in using a almost-static formulation for the friction term, which is only valid for permanent flowing. This paper compares the results obtained from physical model with the one from the mathematical modeling, considering or not a special modeling for transitory friction term. The models used proposed by Brunone et. al. (1991) and Vardy et. al. (1993), to describe the variable friction term / Mestrado / Recursos Hidricos / Mestre em Engenharia Civil

The Inverse Temperature Crystallization (ITC) and seed-induced method were used to grow high-quality cubic samples within hours using a 1M solution of methylammonium lead bromide (MAPbBr3) samples. The current-voltage (I-V) hysteresis observed within the MAPbBr3 perovskite sample demonstrates anomalous dependence on scan rate and various preconditioning pulses. We investigate this dependence and the relationship of current-transient with slow migrating ions. The current transients fitted using a bi-exponential decay model produced two distinct time constants t1 = 38.4 s and t2 = 6.49 s associated with migrating ionic species. From the Arrhenius plot an activation energy of Ea = 0.410 associated with migrating Br ions was extracted. Future research is required towards the understanding of I-V hysteresis and the link to ion migration in MAPbBr3 perovskite. / Dissertation (MSc (Physics))--University of Pretoria, 2020. / NRF Funding / Physics / MSc (Physics) / Restricted

The output characteristics of five compression hearing aids in response to a transient signal were examined to determine if, the input-output function (i.e. output levels of the hearing aid as a function of input level) for a transient signal could be made to approximate that of a continuous signal, by activating the compression circuit with a second signal (activator). Input-output functions for three input compression and two output compression hearing aids were obtained in order to determine if: 1. the automatic gain control (AGC) was activated by the second signal and the transient signal output approximates that of a continuous tone, and 2. if the second tone was evident in the output of the hearing aid and thereby potentially being an interfering factor in aided auditory brainstem response (ABR) measurement.

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