O presente trabalho de pesquisa foi desenvolvido tendo por objetivo estudar e verificar o comportamento da produção de energia elétrica por sistemas de cogeração em duas indústrias de processamento de cana-de-açúcar. As indústrias objeto do estudo situam-se ambas na região Norte do Estado de São Paulo, onde foram coletados dados de cana moída, energia adquirida da concessionária, energia autogerada, potencia média gerada, consumo específico e produção de bagaço referentes ao período 1990-1997. Corn as séries de variáveis, foram elaboradas tabelas resumidas das médias, medianas e desvio-padrão mensais, corn objetivo de se avaliar o comportamento dessas variáveis ao longo das safras, bem como se observar as tendências delineadas pelos dados. O ajustamento de regressão permitiu inferir o grau de aderência dos dados coletados a modelos matemáticos, e a partir destes, verificar o desempenho das duas indústrias em termos de produtividade e viabilidade de produção de energia elétrica excedente. Os resultados obtidos mostram que das duas usinas estudadas, a Usina A praticamente manteve estável os níveis de produção durante todo período de estudo, enquanto a Usina B apresentou um crescimento na produção industrial da ordem de 45% entre as safras inicial e final do estudo. / This research work was developed with the objective study and verify the behavior of the production of electricity by cogeneration systems in two industries processing cane sugar. The object of study industries are located both in the Northern region Sao Paulo, where data were collected from crushed sugarcane, commercially purchased power, self-generated energy, average power generated, specific consumption and bagasse production for the period 1990-1997. Corn sets of variables, the summary tables were prepared mean, median and standard deviation of monthly corn objective of evaluating the behavior of these variables over the crops, as well as observe the trends outlined by the data. The adjustment regression allow us to infer the degree of adherence data collected mathematical models, and from these, check the performance of two industries in terms of productivity and viability of producing electricity surplus. The results show that the two plants studied, The Plant remained practically stable production levels throughout the study period, while Plant B showed a growth in industrial production order of 45% between the initial and final harvests of the study.

No setor elétrico do Peru, o setor residencial de Lima Metropolirana apresenta um grande potencial de conservação de energia, principalmente no serviço de iluminação, além da refrigeração e o aquecimento de água, proporcionalmente pequenos, porém signicativo. Neste trabalho, estima-se o potencial acumulada de conservação de energia elétrica igual a 8:456.9 GWh, no período 1995-2005, como resultado da utilização de tecnologias eficientes no serviços de iluminação, conservação de alimentos e aquecimento de água. Os custos de energia conservada sio inferiores a US$ 0,04/kWh, ou seja, equivalem a 36% do preço de energia elétrica que paga o consumidor residencial (US$ 0,11/kWh). Com a finalidade de superar as barreiras ao uso eciente da energia elétrica no Peru, neste trabalho propõe-se diversas condições que devem estabelecer-se para desenvolver um mercado de tecnologias eficientes com o objetivo de acelerar e aumentar a penetração destas tecnologias no mercado de usos nais de energia elétrica no setor residencial de Lima metropolitana. Analisam-se condições operacionais ao nível de governo, dos fabricantes, das concessionárias e tarifas elétricas, e dos consumidores. / The residential sector in the city of Lima, Peru has a large potential for energy conservation, mainly, for lighting, refrigeration and water heating. While relatively small, savings obtained for these energy services are meaningful. In this work, we assessed a cumulated potential of 8,456.9 GWh for electricity conservation in the period 1995-2005, that might be developed through efficient technologies for residential lighting, food storage and water heatin g. The energy conservation costs are below US$ 0.04/kWh, which is equivalent to 36 percent of the residential electricity rate in Lima (US$ 0.11/kWh). In this work, we discussed some operational conditions for development of a market for energy efficient technologies and equipments that may increase the penetration of those devices for the residential electricity end-use consumption in Lima. The operational conditions for development of such a market have been considered for its four main components, i.e., the power distribution utility, the consumers, the electricity rates, the equipment manufacturers and the governments.

This is a study of potential improvements of diagnostic methods used on high-voltage generators and motors.  It considers offline electrical measurements on the main insulation of stator windings, where a sinusoidal voltage is applied between the winding and the stator-core, and the total current through the insulation (dielectric spectroscopy, DS) and the rapid current-pulses arising from discharges (partial discharge, PD) are measured. The proposed methods differ from existing practice in industrial DS and PD measurements in that the applied voltage is varied in amplitude and in frequency, harmonics of the voltage and current are measured, and the DS and PD measurements are made simultaneously, with comparison of results.  Based on literature, models and measurements, the problems and advantages of these methods are assessed in this work. Harmonics provide a way of separating linear and nonlinear sources of current, and reveal the waveform of the current.  Measurement of total PD charge by DS methods provides complementary information to the conventional PD measurement; the difference in results between these types of measurement is shown by literature and experimental results to be large.  Simultaneous measurement allows direct comparison of the relation between the DS and PD results, and saves time compared to separate measurements.  The varied frequency, down to the millihertz range, provides additional information about the insulation.  Much of the potential for DS methods on machine insulation is spoiled by the end-winding stress grading.  Models and measurements of the currents in this grading are presented, with discussion of how much effect the disturbance has and how well it can be predicted by modelling. / QC 20100906

The response of a cable can be used to analyze the variation of the material characteristics along its length. For diagnosis of possible ageing, it is necessary to know how cable design, material properties and cable insulation ageing affects the wave propagation. A cable model has therefore been worked out based upon the high frequency properties of the cable insulation and conductor systems. The high frequency characteristics of the semi-conducting screens, new and water-tree aged cross-linked polyethylene (XLPE) insulation have been determined by two measuring techniques. Semi-conducting screens have a great influence on the attenuation of cables at high frequencies. A dielectric function based on an empirical formula is fitted to the measured characteristics of the semi-conducting screens. The dielectric function is used in the cable model set-up to predict the propagation constant of the cables. The high frequency characteristics of the water-tree degraded XLPE insulation obtained from measurements are related to the water content of the water trees of the samples. An effective materials model is developed to estimate the water content of the water trees and the conductivity of the water. The propagation constant from the cable model is compared to the propagation constant obtained from measurements made on cables. Using approximate high frequency cable models, the relative contributions of the conductor and insulation systems to the attenuation and phase velocity of the cables are analyzed. / QC 20101018

At the Division of Electricity at UppsalaUniversitythere are ongoing researches, including a research concerning turbo generators. Turbo generators produce a large share of electricity in the world; however they are costly mainly due to the fact that the cooling and ventilation that are needed to eliminate the excess heat from the generators are expensive. Turbo generators work with high efficiency and in this project, the main task is to simulate a generator while taking into account that the generator must be designed against self-oscillation, centrifugal force, exhaustion and heat. The turbo generator must be simulated without being too expensive and complicated. In this project, the dimensions of the turbo generator depend on the efficiency of it, and where the losses are in the generator. Furthermore, the optimum values need to be chosen with the help of the ACE simulation program. The report begins with an introduction describing the project followed by a task description that is dealing with the project. The project aims to obtain an optimal design that is simple to construct, with good durability and preferably at a reasonable cost. The function of the turbo generator has been studied, as well as the FEM calculations that affect the durability and structural strength of the generator. In this report you can further read more in detail about the methods used and how solutions were reached to solve the problems that were encountered. The conclusion of this project was that the turbo-generator which were simulated is a turbo-generator that has a lower load angle compared with Björn Bolund turbo-generator. It also has a high efficiency which makes it more stable than Björn Bolund and the high efficiency makes it save energy and cooling equipment.

<p>The response of a cable can be used to analyze the variation of the material characteristics along its length. For diagnosis of possible ageing, it is necessary to know how cable design, material properties and cable insulation ageing affects the wave propagation. A cable model has therefore been worked out based upon the high frequency properties of the cable insulation and conductor systems. The high frequency characteristics of the semi-conducting screens, new and water-tree aged cross-linked polyethylene (XLPE) insulation have been determined by two measuring techniques. Semi-conducting screens have a great influence on the attenuation of cables at high frequencies.</p><p>A dielectric function based on an empirical formula is fitted to the measured characteristics of the semi-conducting screens. The dielectric function is used in the cable model set-up to predict the propagation constant of the cables.</p><p>The high frequency characteristics of the water-tree degraded XLPE insulation obtained from measurements are related to the water content of the water trees of the samples. An effective materials model is developed to estimate the water content of the water trees and the conductivity of the water.</p><p>The propagation constant from the cable model is compared to the propagation constant obtained from measurements made on cables. Using approximate high frequency cable models, the relative contributions of the conductor and insulation systems to the attenuation and phase velocity of the cables are analyzed.</p>

<p>Offshore wind farms have recently emerged as promising renewable energy sources. For increasing distances between offshore generation and onshore distribution grid, HVDC transmission systems based on voltage source converters can be a feasible and competitive solution. This thesis presents a comprehensive evaluation of a novel integrated wind farm topology that includes the generator drive system, the turbine interconnection and the HVDC transmission.</p><p>In the proposed concept, every wind turbine is connected to a single-phase medium-frequency collection grid via a distribution transformer and a cycloconverter, which allows the wind turbines to operate at variable speed. The collection grid is connected to an HVDC cable via a transmission transformer and a single-phase voltage source converter. This thesis evaluates in detail the principle of operation, which is also verified with system simulations in PSCAD.</p><p>The proposed concept promises several potential benefits. Converter switching losses and stress on the semiconductors for example can be considerably reduced by applying a soft-switched commutation scheme in all points of operation. Single-phase medium-frequency transformers have comparably low losses and their compact size and low weight implies an important benefit in an offshore environment. In addition, the voltage source converter is considerably simplified by the reduction to one phase leg, which implies a substantial cost saving.</p><p>Several technical challenges are identified and critically evaluated in order to guarantee the feasibility of the proposed concept. Especially the design of the medium-frequency collection grid is crucial as unwanted system resonances can cause dangerous overvoltages. Most of the technical challenges concern the specific characteristics of the proposed concept. The insulation of the single-phase medium-frequency transformers for example needs to withstand the high voltage derivatives. This thesis contains also considerations regarding the dimensioning and optimization of different system components.</p><p>A survey of different transmission systems for the grid connection of wind farms shows the potential of the proposed concept, which addresses several problems associated with electrical systems of wind farms. Both the requirements for variable-speed operation of the wind turbines and an interface for HVDC transmission are fulfilled in a cost-effective way. Compared to conventional voltage source converter based HVDC transmission systems, the initial costs are reduced and the expected annual energy production is increased. In addition, the proposed voltage source converter based HVDC transmission system can fully comply with recent requirements regarding the grid connection of wind farms.</p>

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 171-175). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Feb. 3, 2010). Bibliography: leaves 97-101.

Thesis (M.S.)--Tennessee Technological University, 2008. / Title from title page screen (viewed on Mar. 18, 2010). Includes bibliographical references.