Os transformadores de potência são alguns dos elementos mais importantes dos sistemas elétricos. A confiabilidade e o bom funcionamento destes equipamentos são vitais para que as companhias de energia forneçam eletricidade com qualidade e segurança. Um dos principais parâmetros que envolvem a normalidade da operação dos transformadores é o estado da isolação interna formada pelo óleo mineral e o papel que cobre as bobinas. Danos nessa isolação resultam na degradação destes dielétricos e, por conseqüência, na diminuição da vida útil dos transformadores. Essa degradação, que advém de processos elétricos, térmicos, ou mesmo mecânicos, geram gases combustíveis cujas quantidades individuais podem indicar o tipo de falha e a gravidade do problema. Desta forma, é importante detectar os principais gases envolvidos. O objetivo deste trabalho é realizar análises e estudos quantitativos da presença de gases inflamáveis dissolvidos no óleo, surgidos através da degradação deste líquido isolante. O cerne deste trabalho está em elaborar ensaios de formação de arco no óleo e, posteriormente, aquecer o fluido para medir a quantidade dos gases combustíveis antes dissolvidos nele. Este estudo visa à melhoria na confiabilidade dos equipamentos projetados para detectar e monitorar o surgimento de gases inflamáveis no interior de transformadores de potência existentes em subestações de companhias de eletricidade. / Power transformers are some of the most important elements of electrical systems. The trustworthiness and the good functioning of this equipment permit power utilities to supply electricity with quality and security. One of the main parameters for transformer\'s operation normality is the state of the internal insulation formed by the mineral oil and the paper that covers the bobbins. Damages in this insulation cause its dielectric degradation and, consequently, the reduction of the equipment useful life. This degradation which originates from electrical, thermal, or even mechanical processes generates chemical products such as gases whose individual amounts may indicate the type of imperfection and gravity of the problem. That\'s why the detection of the main involved gases is important. This work intends to elaborate analyses and studies of the presence of inflammable gases dissolved in oil through the degradation of the insulating liquid. The principal topic of this work is the arc formation elaboration in the oil and later the heating of the oil to measure the amount of gases previously dissolved in it. This study also aims to improve the trustworthiness of the projected equipments in order to detect and monitor the sprouting of existing inflammable gases in the interior of power transformers in substations of power utilities.

Submitted by Gizele Lima (gizele.lima@inpa.gov.br) on 2017-11-03T15:04:48Z No. of bitstreams: 2 Tese_Sonaira_Silva_05-10-17.pdf: 11601812 bytes, checksum: 0127560ec4ee85719f0e6389dc72f9cd (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-11-03T15:04:48Z (GMT). No. of bitstreams: 2 Tese_Sonaira_Silva_05-10-17.pdf: 11601812 bytes, checksum: 0127560ec4ee85719f0e6389dc72f9cd (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-08-17 / Over the last 40 years, forest fires in Amazonia have occurred at intervals of 4 to 5 years, causing economic, environmental and social damage. To understand the spatial and temporal dynamics of forest fires in Brazil’s state of Acre over a period of 33 years (1984 to 2016), we used images from Landsat 5, 7 and 8, applying the burn scar index (BSI) derived from the fractions of photosynthetic material, non-photosynthetic material and soil generated by CLASlite© software. Based on this mapping, we used the weights of evidence method in Dinamica-EGO software to analyze the factors resulting from human action and from natural features of the landscape that have the strongest influence on the occurrence of forest fires. To understand the changes in the forest, we selected four areas based on mapping the 2005 and 2010 fires and their areas of overlap. In this forest inventory we measured the diameter at breast height of all living and dead individuals larger than 10 cm in diameter in three 100 m × 50 m plots and all bamboo culms independent of diameter in 5 m × 5 m sub-plots. Information was collected on the total height of trees, whether the trees were broken or pressured by bamboo and whether termites were present. The total area of forest impacted by the fire in the period of 33 years in the entire State of Acre was 5,251 km 2 . However, of this total there were forests that were affected by fire only once (3,883 km 2 ), twice (598 km 2 ) and three times (57 km 2 ). In 2005, the municipalities (counties) of Acrelândia, Plácido de Castro and Senador Guiomard had more than 50% of their remaining forest impacted by fire. The main factors favoring fire occurrence were fragmentation and the proximity of cattle pastures and roads. Forest types most susceptible to fire were open forest with bamboo, open forest with palms and alluvial forest. Degradation caused by fire caused a strong impact in the reduction of density trees, species richness and decreases in dry above-ground biomass. An additional effect of the impact of the fire was an expansion of bamboo to densities 7 to 9 times that in unburned forest. The expansion of the bamboo had a linear relationship with decrease in the number of trees, in addition to increasing the number of trees damaged and broken, affecting up to 24% of all trees. For the open forests of southwestern Amazonia it is important to consider the contribution of bamboo (Guadua) in estimates of the total above-ground biomass of the forest. Bamboo increases the total biomass by 3 Mg ha -1 in intact forest, 26 Mg ha -1 in forest burned in 2005, 23 Mg ha -1 in forest burned in 2010 and 26 Mg ha -1 in forest burned in both 2005 and 2010, raising the biomass by percentages ranging from 1% to 38% with respect to the tree component. Up to 2016, the reduction of forest biomass caused a committed emission of 38 Tg of CO 2 for the state of Acre in an area of 3800 km 2 of remaining forest that had been affected by fire. This Xcommitted emission reduces by 17% the net climatic benefit of Acre’s goal for reducing the state’s greenhouse-gas emissions by 2020. This study made it possible to understand the scale of forest fires and their impacts in the forests of the state of Acre in drought years, which points to a future full of challenges for reducing the process of forest degradation. / Nos últimos 40 anos, os incêndios florestais têm ocorrido em intervalo de 4 a 5 anos em diferentes regiões da Amazônia brasileira, causando danos econômicos, ambientais e sociais. Para compreender a dinâmica espaço-temporal dos incêndios florestais no Estado do Acre, foi analisado um período de 33 anos (1984 a 2016) de imagens Landsat (5, 7 e 8) através da aplicação do Índice de Cicatriz de Fogo (Burn Scar Index – BSI) derivado das frações de Material Fotossintético, Não-Fotossintético e Solo, geradas pelo software CLASlite©. Com base neste mapeamento, analisamos os fatores fruto da ação antrópicas e características naturais da paisagem que mais influenciam a ocorrência dos incêndios florestais pelo software Dinamica EGO através do método de pesos de evidência. Para compreender as mudanças na floresta, selecionamos quatro áreas com base no mapeamento dos incêndios de 2005 e 2010 e sua reincidência. Neste inventário florestal medimos o diâmetro a altura do peito de todos os indivíduos vivos e mortos maiores que 10 cm em três parcelas de 100 m × 50 m e todos os colmos vivos de bambu independentes do diâmetro em sub-parcelas de 5 m × 5 m em floresta intacta (testemunha), floresta queimada em 2005, floresta queimada em 2010 e floresta queimada em 2005 e 2010. Foram coletadas informações sobre a altura total, árvores quebradas ou danificadas pelo bambu, presença de cupim e infestação de cipós na copa das árvores. A área total de floresta impactada pelo fogo no período de 33 anos em todo o Estado do Acre foi de 5.251 km 2 . No entanto, deste total houve florestas que foram afetadas pelo fogo somente uma vez (3.883 km 2 ), duas vezes (598 km 2 ) e três vezes (57 km 2 ). Em 2005, os municípios de Acrelândia, Plácido de Castro e Senador Guiomard tiveram mais de 50% do remanescente florestal impactado pelo fogo. Os principais fatores que favoreceram à ocorrência de incêndios florestais foram: a fragmentação, proximidade de florestas às áreas de pastagens e estradas. A maior ocorrência dos incêndios foi atribuída às florestas abertas com bambu e palmeira e florestas aluviais. A degradação florestal ocasionada pelo fogo causou a redução na densidade de árvores, na redução da riqueza de espécies e redução na biomassa seca acima do solo. Entretanto, houve aumento no número de espécies pioneiras. Observou-se um efeito adicional ao impacto do fogo, uma expansão da densidade de colmos de bambu na proporção de 7 a 9 vezes com relação a floresta intacta. A expansão do bambu teve relação linear com a redução do número de árvores, além de aumentar o número de árvores danificadas e quebradas, afetando até 24% do total de árvores. Para as florestas abertas da Amazônia Sul Ocidental é importante considerar a contribuição da biomassa do bambu (gênero Guadua) para estimativa da biomassa total da floresta acima do solo. O bambu aumentou a biomassa total em 3 Mg ha -1 na floresta intacta, 26 Mg ha -1 na floresta queimada em 2005, 23 Mg ha -1 na floresta queimada em 2010 e 26 Mg ha -1 na floresta queimada reincidente, elevando a biomassa em termos percentual de 1% a 38% com relação ao componente arbóreo. Até 2016, a redução da biomassa florestal causou uma emissão comprometida de 38 Tg de CO 2 para o Estado do Acre em uma área de floresta remanescente afetada pelo fogo de 3.800 km 2 . Esta emissão significa um comprometimento de 17% da meta de redução de gases de efeito estufa do Acre até 2020. Este estudo possibilitou compreender a dimensão dos incêndios florestais e os seus impactos nas florestas do Estado do Acre em anos de secas extremas, possibilitando visualizar um futuro cheio de desafios para redução do processo de degradação florestal.

Orientador: Antônio André Chivanga Barros. / Dissertação (mestrado) - Universidade Regional de Blumenau, Centro de Ciências Tecnológicas, Programa de Pós-Graduação em Engenharia Ambiental.

Tese de mestrado. Engenharia de Segurança e Higiene Ocupacionais. Faculdade de Engenharia. Universidade do Porto. 2008

Dissertação apresentada para obtenção do grau de Doutor, na Faculdade de Engenharia da Universidade do Porto

Tese de doutoramento. Engenharia Química e Biológica. Faculdade de Engenharia. Universidade do Porto. 2010

Tese de doutoramento. Engenharia Química. 1979. Department of Chemical Engineering and Chemical Technology. Imperial College of Science and Technology

No description available.

A life cycle study was undertaken to assess the economic impact arising from internalised embodied greenhouse gas emissions (GGE) costs for a commercial office building. A limited range of design and materials re-cycling strategies were investigated for their abatement potential. GGE quantities were determined by a hybrid process analysis where input-output data was supplemented with national average data to increase completeness whereby all upstream emissions arising from material inputs to the point of extraction, as well as non-material inputs (e.g. goods and services) into the design and construction process are accounted for. The hypothesis proposed abatement potential of 30%, as measured against the Benchmark Design (BM) would be economically viable in absence of the benefit of early-action credits. The hypothesis was disproved with 15% abatement shown at zero additional capital cost. A Stretch Technology (ST) scenario was investigated which showed 32% abatement potential however the associated marginal capital cost could not be determined. The GGE intensity per meter square of Net Lettable Area (m2 NLA) for the case study building was found to be 5,258 kg CO2-e. The theoretical value of abatement credits was determined at $12 to $1,031 / m2 NLA (depending on price) and is shown to present a reasonable economic and market transformation opportunity at medium range values. The results demonstrate that the cost-push inflation risk posed to commercial office construction is large where the price of embodied GGE is internalised in the economic system. Gross Construction Cost (GCC) increase per square meter is shown to be between 1.5% and 61% (with associated negative IRR impacts between -0.1 to -7%) depending on the GGE price level. An unsustainable cost impact is demonstrated at GGE prices greater than AUD$50 per tonne of carbon dioxide equivalent (AUD$50/ tonne CO2-e). Internalised GGE studies have been largely limited to the operational cost impact arising from GGE of direct end-use rather than from the perspective of total embodied final demand. The results demonstrate the critical nature of embodied abatement strategies for commercial buildings if the internationally accepted 60% global GGE abatement is to be achieved within the relevant timeframe. An average kg CO2-e intensity per dollar of GCC is proposed for the three building models that may be applied to general scenario planning. The scale of economic benefit available for embodied credits is significant and the determination of viable credit mechanisms worthy of further research.

In this work the phase behaviour of noble gases is studied comprehensively by different molecular simulation methods using different intermolecular potentials. The aim is to investigate three-body effects on the phase behaviour of noble gases. A true two-body potential model (Barker-Fisher-Watts potential) and the three-body potential model (Axilrod-Teller term) have been used. The results obtained from the two-body BFW potential with the three-body Axilrod-Teller potential included for the vapour-liquid and solid-liquid phase equilibrium properties of pure noble gases are compared with the calculations using the Lennard-Jones potential with different suggested parameter values. The results have been compared with experimental data and the best parameter values for simulating the thermodynamic properties of noble gases are found. Three-body effects on the phase behaviour of noble gases are reported for a large range of density, temperature and pressure. Simple relationships have been found between two-body and three-body potential energies for pure fluids and solids. Three-body effects on the vapour-liquid phase equilibrium properties of argon, krypton, xenon and argon-krypton systems are studied by the Gibbs-Duhem integration Monte Carlo method. Three-body effects on the solid-liquid phase equilibrium properties of argon, krypton and xenon are investigated by non-equilibrium and equilibrium molecular dynamics techniques. All the calculations have been compared with experimental data, which show that three-body interactions play an important role in the overall interatomic interactions of noble gases.