Navegando por Assunto "Transmission lines (energy)"

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Acesso aberto (Open Access)
Modelagem de par-trançado para comunicações em banda larga
(Universidade Federal do Pará, 2016-03-07) BORGES, Gilvan Soares; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
Ultimately, the purpose of a model for transmission lines is to describe how the transmission properties of a line are frequency dependent. The sources of such dependency can be grouped in two areas: that one related to longitudinal changes on the line geometry and constituting materials (non-uniformities), and that related to electromagnetic phenomena such as the skin effect and the dielectric dispersion (present even when the line is uniform). The contribution of this thesis is related to the above mentioned areas, focused on a specific type of transmission line, the twisted-pair. The models for twisted pairs found in literature assume simplistic considerations which are not always realistic, e.g., they ignore that the dielectric medium is heterogeneous and with losses, ignore the effect of the non-uniformities that are inevitable to all transmission lines, etc. These and other issues are taken into account during the development of a new twisted-pair model. This model is composed for two components, a deterministic one which is a function of the constructive characteristics of the twisted-pair, and a stochastic one which is a function of the inherent defects in twisted-pair cables. Regarding the deterministic component, it employs a realistic and straightforward approach to describe: the proximity effect of the conductors, the presence of conductors’ insulation, the dielectric losses and pair twisting. As a result, the model is more accurate than the models from the literature. Regarding the stochastic component, it was not found in literature similar models for comparison. Nevertheless, it was shown that the proposed stochastic model has good agreement with experimental observation.
Acesso aberto (Open Access)
Solução estrutural para a segurança do suprimento de energia elétrica no estado do Amazonas
(Universidade Federal do Pará, 2009-12-17) FROTA, Willamy Moreira; ROCHA, Brigida Ramati Pereira da; http://lattes.cnpq.br/9943372249006341
The electric energy vector assumes significant importance in the process of the Amazon integration to the national development. The electric energy support on this region, reaches a high priority level among the constitutional objectives on reduction the regional differences (FROTA, 2004). In the Amazon state, it can be stated that the lack of energy is a fact that decreases the regional development, and in many locations, smaller and more isolated, a factor of social, economic and cultural marginalization. The historical situation of the increasing use of fuel derived petroleum to the power generation in the Amazon state brings huge economic and environmental damage to the Brazilian society, and it has to be solved by the energetic Brazilian planning organ, by imposing the need of reaching other cleaner, safer and less expensive sources. The state is different from other regions of the country due to the existence of several isolated systems, mainly from its capital, Manaus, that shows low reliability and quality in its energy service, adding to that the high cost, considering the need of thermal diesel and oil generation, their amount represents about 73% of all fuel that have to be used in Brazil to thermoelectric power generation (GTON, 2009), having a final cost of 3 billions (US$ 1.5 billion) which is supported, most of it, by the sources transferences obtained through the subsidies of the Consumption Account of Fossil Fuels - CCC. Having this in mind, this assignment has as objective to present an approach of the mainly existing problems, as well as a proposal of structural solution for the energy business to the Amazon state, that can contribute to the improvement of the principles that rule, the compatible energetic politics with the goals of the updated institutional model of the Brazilian electric sector, giving birth to a new cycle of development and growing to the Amazon state and to the Amazon region.