A função básica de um sistema de energia elétrica é fornecer aos seus clientes energia elétrica economicamente e tão confiável quanto possível. A importância da confiabilidade dos sistemas de energia elétrica é claramente notada quando as pessoas são confrontadas com a perda de energia elétrica, não importando se a perda provoca parada das linhas de produção ou mesmo impactos financeiros às empresas, o que pode consequentemente causar enorme impacto econômico além de situações que impactam o conforto da população. Dentro deste contexto esta tese apresenta uma metodologia para avaliação da confiabilidade de plantas de geração de energia elétrica que possibilita avaliar qualitativamente e quantitativamente a confiabilidade e disponibilidade dos principais componentes elétricos e mecânicos necessários à geração confiável de energia. A análise qualitativa foi realizada levando-se em consideração as características físicas das usinas hidroelétricas e as características construtivas das unidades geradoras para que fosse possibilitada a classificação das unidades geradoras em grupos estatisticamente significativos. A análise quantitativa foi fundamentada em métodos estatísticos de estimação e inferência e aspectos relacionados ao desempenho e disponibilidade de usinas hidroelétricas brasileiras tendo como referência os índices preconizados pelas agências regulatórias. As unidades geradoras foram modeladas através de métodos estatísticos e probabilísticos que permitem avaliar por meio de técnicas de confiabilidade a frequência e a duração das falhas além das probabilidades associadas a cada estado de falha. Os dados de falha foram obtidos por meio de bancos de dados consolidados por agentes geradores e órgãos federais responsáveis pela operação do sistema interligado nacional. Os dados representam a história operativa de grande parte das usinas hidrelétricas brasileiras operadas e despachadas de forma centralizada. A metodologia apresentada nesta tese preenche uma lacuna na existência de metodologias focadas em avaliação de confiabilidade de plantas de geração em fase de projeto, que possibilitariam a mitigação de riscos de falhas e perdas produtivas quando da operação comercial da planta de geração. / The basic function of a power system is to provide their customers electricity as economically and reliably as possible. The importance of the reliability of electric power systems is clearly noted when people are confronted with the loss of energy, no matter if the loss stops the production lines or even causes financial impacts on companies, which may consequently cause huge economic impact beyond situations that influence the comfort of the population. Within this context, this thesis presents a methodology for assessing the reliability of plants generating electricity that enables qualitatively and quantitatively evaluate the reliability and availability of key electrical and mechanical components needed to generate reliable power. Qualitative analysis was performed taking into account the physical characteristics of hydroelectric and constructive features of the generating units to which the classification was made to enable pool and cluster generating units in groups statistically significant. Quantitative analysis was based on statistical methods of estimation and inference and aspects related to performance and availability of Brazilian hydroelectric plants with reference to the indices recommended by regulatory agencies. The units were modeled using probabilistic and statistical methods for assessing, by means of reliability techniques, the frequency and duration of failures plus the probabilities associated with each state of failure. The failure data were obtained from consolidated databases by agents and federal agencies responsible for the operation of the national grid. The data represent the operational history of much of Brazil\'s hydroelectric facilities operated and dispatched centrally. The methodology presented in this thesis fills a gap in the existence of methodologies focused on reliability assessment of power plants in the design phase, which would allow the mitigation of risks of failures and production losses when the commercial operation of the generating plant.

A função básica de um sistema de energia elétrica é fornecer aos seus clientes energia elétrica economicamente e tão confiável quanto possível. A importância da confiabilidade dos sistemas de energia elétrica é claramente notada quando as pessoas são confrontadas com a perda de energia elétrica, não importando se a perda provoca parada das linhas de produção ou mesmo impactos financeiros às empresas, o que pode consequentemente causar enorme impacto econômico além de situações que impactam o conforto da população. Dentro deste contexto esta tese apresenta uma metodologia para avaliação da confiabilidade de plantas de geração de energia elétrica que possibilita avaliar qualitativamente e quantitativamente a confiabilidade e disponibilidade dos principais componentes elétricos e mecânicos necessários à geração confiável de energia. A análise qualitativa foi realizada levando-se em consideração as características físicas das usinas hidroelétricas e as características construtivas das unidades geradoras para que fosse possibilitada a classificação das unidades geradoras em grupos estatisticamente significativos. A análise quantitativa foi fundamentada em métodos estatísticos de estimação e inferência e aspectos relacionados ao desempenho e disponibilidade de usinas hidroelétricas brasileiras tendo como referência os índices preconizados pelas agências regulatórias. As unidades geradoras foram modeladas através de métodos estatísticos e probabilísticos que permitem avaliar por meio de técnicas de confiabilidade a frequência e a duração das falhas além das probabilidades associadas a cada estado de falha. Os dados de falha foram obtidos por meio de bancos de dados consolidados por agentes geradores e órgãos federais responsáveis pela operação do sistema interligado nacional. Os dados representam a história operativa de grande parte das usinas hidrelétricas brasileiras operadas e despachadas de forma centralizada. A metodologia apresentada nesta tese preenche uma lacuna na existência de metodologias focadas em avaliação de confiabilidade de plantas de geração em fase de projeto, que possibilitariam a mitigação de riscos de falhas e perdas produtivas quando da operação comercial da planta de geração. / The basic function of a power system is to provide their customers electricity as economically and reliably as possible. The importance of the reliability of electric power systems is clearly noted when people are confronted with the loss of energy, no matter if the loss stops the production lines or even causes financial impacts on companies, which may consequently cause huge economic impact beyond situations that influence the comfort of the population. Within this context, this thesis presents a methodology for assessing the reliability of plants generating electricity that enables qualitatively and quantitatively evaluate the reliability and availability of key electrical and mechanical components needed to generate reliable power. Qualitative analysis was performed taking into account the physical characteristics of hydroelectric and constructive features of the generating units to which the classification was made to enable pool and cluster generating units in groups statistically significant. Quantitative analysis was based on statistical methods of estimation and inference and aspects related to performance and availability of Brazilian hydroelectric plants with reference to the indices recommended by regulatory agencies. The units were modeled using probabilistic and statistical methods for assessing, by means of reliability techniques, the frequency and duration of failures plus the probabilities associated with each state of failure. The failure data were obtained from consolidated databases by agents and federal agencies responsible for the operation of the national grid. The data represent the operational history of much of Brazil\'s hydroelectric facilities operated and dispatched centrally. The methodology presented in this thesis fills a gap in the existence of methodologies focused on reliability assessment of power plants in the design phase, which would allow the mitigation of risks of failures and production losses when the commercial operation of the generating plant.

Electricity generating units (EGUs) are major emitters of both nitrogen oxides (NOx) and CO₂, and cap-and-trade programs are either currently used or proposed as management strategies for both pollutants. Emission cap and trade programs for these two pollutants have generally been considered independently, but since each EGU will have a characteristic NOx to CO₂ emission ratio, these programs are inherently connected. This thesis examines the extent to which CO₂ emission pricing and NOx emission markets are likely to influence each other, using Texas as a case study. The relationship is first demonstrated with a simple scenario of four power plants, followed by a second scenario accounting for the largest 34 plants in Texas. The analysis demonstrates that future CO₂ pricing will cause NOx emissions markets to be inefficient at reducing emissions through changes in the dispatching order. There will also exist a greater potential for NOx price spikes. Two plausible alternatives to this problem are suggested: a temporally- and spatially-variable NOx program, or increased emphasis on retrofitting the existing fleet of power plants for NOx reduction. / text

Elevated concentrations of ambient fine particulate matter (PM2.5) and ozone (O3) contribute to adverse health outcomes in exposed populations. Anthropogenic source sectors, including aviation, residential combustion (RC), and electricity generating units (EGUs), lead to increased concentrations of these combustion-related pollutants. Quantification of the influence of emissions from specific source sectors on ambient pollutant concentrations can be very useful in better informing public health policy decision making on air quality improvements. Due to complex emissions dynamics, background concentrations, and meteorology, determining contributions of these sources to related health risks is challenging. To assess local impacts of aviation activity, concentrations of nitrogen oxides (NOx) and the PM2.5 constituent black carbon (BC) were monitored near airports. Moreover, aviation-attributable fractions were derived from monitored concentrations using regression modeling, and values were compared with predicted aviation-attributable concentrations from a near-field dispersion model. Regional impacts of aviation, RC, and EGUs were assessed using the Community Multiscale Air Quality (CMAQ) atmospheric chemistry and transport model with the Direct Decoupled Method (DDM) to determine sensitivity of ambient PM2.5 and O3 concentrations to emissions from individual sources. Health damage functions, quantified as mortality per thousand tons of emitted precursor species, were created by individual airport for 66 of the highest fuel-burning airports in the United States and by state for RC and EGUs. Physically-interpretable regression models were built to predict aviation-related health damage functions. With local aviation, comparisons of regression-predicted and dispersion-predicted BC and NOx concentrations are similar when aggregated, though diurnal patterns show potential weaknesses in near-field dispersion and emissions inventory accuracy. For regional aviation impacts, health damage function values varied by more than an order of magnitude across airports for each precursor-ambient pollutant pair, with seasonal effects present in secondary pollutant formation. Health damage functions were predicted by combinations of upwind and downwind population, meteorology, and atmospheric chemistry regime. State-resolution contributions of RC and EGUs varied both within and between source sectors, based on local characteristics including population density and EGU location. These findings reinforce the importance of quantification of source-specific air quality and health impacts in the design of health-maximizing emissions control policies.

I och med införandet av IFRS år 2005 måste noterade koncernföretag numera årligen nedskrivningspröva goodwill istället för att göra avskrivningar, vilket tidigare varit tillåtet. De antaganden som ligger till grund för nedskrivningsprövningen baseras på företagsledningars uppskattningar av framtiden, vilket kan leda till subjektiva bedömningar. När IFRS infördes befann sig Sverige i en högkonjunktur, fram tills år 2008 då den globala finanskrisen uppstod och därav efterföljande lågkonjunktur. Då tidigare studier har visat att en finanskris kan leda till att företag behöver göra nedskrivningar på både finansiella och icke-finansiella tillgångar, vill författarna undersöka om finanskrisen 2008 påverkade företagens nedskrivningar av goodwill. Eftersom det finns skillnader mellan industribranschen och IT- och telekombranschen när det gäller redovisning av goodwill är det intressant att jämföra dessa branscher med varandra.Syftet med studien är att undersöka hur den senaste finanskrisen år 2008 påverkade företagens nedskrivningar av goodwill och antagandena vid nedskrivningsprövning, samt i vilken omfattning företag upplyste om nedskrivningarna före och efter finanskrisen för att se om det finns några signifikanta skillnader mellan industribranschen och IT- och telekombranschen. De företag som har ingått i undersökningen är företag som är noterade på Stockholmsbörsen. Genom en kvantitativ studie har författarna valt att granska årsredovisningar från 15 företag inom industribranschen och 15 företag inom IT- och telekombranschen för åren 2006, 2007, 2009 och 2010. Författarna har som forskningsmetod valt att använda sig av en kvantitativ innehållanalys samt utfört statistiska beräkningar. De parametrar som undersökts är upplysningar om goodwill, totala nedskrivningar, diskonteringsräntor, tillväxttakt och kassagenererande enheter.Det var endast en av studiens hypoteser som stämde och det var att diskonteringsräntorna före jämfört med efter finanskrisen skiljde sig signifikant mellan de två undersökta branscherna. En annan skillnad som var signifikant var industriföretagens totala nedskrivningar före och efter finanskrisen, där den branschens totala nedskrivningar ökade mellan de undersökta perioderna. Den genomsnittliga diskonteringsräntan inom IT- och telekombranschen ökade mellan de undersökta perioderna, vilket också konstaterades vara signifikant. Vidare visade studien att industribranschen redovisade mer omfattande upplysningar om goodwillnedskrivningar efter finanskrisen jämfört med perioden innan, till skillnad från IT-och telekombranschen som redovisade upplysningar om goodwillnedskrivningar i mindre omfattning efter finanskrisen. / IFRS 3 has had a big impact on how listed companies treat the recognition of goodwill. The underlying assumptions of the impairment tests are based on management’s estimates of the future, which could lead to subjective evaluations. When IFRS was introduced in 2005 Sweden was in a boom period, up until 2008 when the global financial crisis emerged and hence subsequent recession. A financial crisis may lead to the needs to make write-downs on both financial and non-financial assets. Therefore the authors want to examine in what way the financial crisis in 2008 affected companies' goodwill impairments. Since there are differences between the industrial sector and the IT and telecommunications sector in terms of accounting for goodwill, it is interesting to compare these sectors to examine if there are any significant differences.The purpose of the study is to examine how the recent financial crisis in 2008 affected companies' impairments of goodwill and assumptions in impairment testing, as well as the extent to which businesses disclosed about the impairment losses before and after the financial crisis to see if there are any significant differences between the industrial sector and the IT and telecommunications sector. The companies that are included in the study are companies that are listed on the Stockholm Stock Exchange. With a quantitative method, the authors have chosen to examine the annual reports of 15 companies in the industrial sector and 15 companies in the IT and telecommunications sector from the years 2006, 2007, 2009 and 2010. The authors have chosen as methods for the research a quantitative content analysis and performed statistical calculations. The parameters studied include disclosure on goodwill, total impairment losses, discount rates, growth rates and cash-generating units.It was only one of the study’s hypotheses that was correct. This hypothesis dealt with the discount rates before and after the financial crisis, were the study showed a significant difference between the IT and telecommunications sector and the industrial sector before the financial crisis compared to the period after the financial crisis. Another difference that was significant was the industrial sectors total impairment losses before and after the financial crisis, were the sector’s total impairment losses increased between the examined periods. The average discount rate in the IT and telecommunications sector increased between the examined periods and this difference was also considered to be significant. Furthermore, the study showed that the industrial sector had more extensive disclosure on goodwill impairments after the financial crisis compared with the previous period, unlike the IT and telecommunications sector that disclosed about goodwill impairments to a lesser extent after the financial crisis.This thesis is written in Swedish.

Orientadores: Secundino Soares Filho, Takaaki Ohishi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-06T02:53:29Z (GMT). No. of bitstreams: 1 ArceEncina_AnastacioSebastian_D.pdf: 1529112 bytes, checksum: a6a22a9ce6cd536449dd06144205c2e5 (MD5) Previous issue date: 2006 / Resumo: A Programação diária de um sistema de energia elétrica busca obter um despacho de geração para o próximo dia, que seja compatível com as metas definidas pelo Planejamento energético e que sirva como referência operativa para a operação em tempo real. Assim, a modelagem do sistema deve ser detalhada levando em consideração as características dos sistemas de geração, de transmissão, requisitos do mercado, critérios de segurança e custos associados à operação. Este trabalho apresenta um modelo de despacho ótimo de unidades geradoras hidrelétricas que adota como critério de desempenho um modelo que avalia as perdas no sistema de geração, ocasionadas pela elevação do nível de canal de fuga, pela variação do rendimento do conjunto turbina-gerador e pelo atrito do fluxo d¿água nas tubulações do sistema hidráulico. Além das perdas no sistema de geração também forma parte do critério de desempenho o custo associado à partida e parada das unidades geradoras. Na formulação do problema, verifica-se a presença de variáveis inteiras, não lineares; restrições de atendimento à demanda, de meta de geração oriunda do Planejamento energético e restrições de capacidade de geração. Isto caracteriza o problema do despacho de unidades geradoras como sendo um problema de programação misto inteiro-não linear, combinatório e de grande porte quando considerado um sistema de geração como o do Sistema Elétrico Brasileiro. Como técnica de solução foi adotada uma heurística que combina Relaxação Lagrangeana e Programação Dinâmica. A metodologia foi aplicada a uma parte do sistema de geração do Sistema Elétrico Brasileiro, composta por 78 usinas hidrelétricas e o total de 398 unidades geradoras. Tomando como referência os dados de programação de um dia típico de operação, os resultados apontam ganhos significativos pela diminuição de perdas. Verifica-se também a importância de se considerar o custo das partidas e paradas no despacho das unidades geradoras / Abstract: The daily scheduling operation of the electrical energy system has by target to find the dispatch generation to the next day which must be compatible with the daily generation target defined by the energy planning models and to be an operational guide. Because of its proximity with the real time operation the modeling must represent the main characteristic of the generation and transmission systems, requirements market¿s, security criterion and operational costs. This work is concerned with the dispatch of hydro generating units. The performance criterion adopted takes into account variations in tailrace elevation, penstock head losses, turbine-generator efficiencies and start-up and shutdown costs. In the hydro generating units dispatch problem formulation there are integer, non-linear variables, constraints concerned with the generation capacity, load attainment and daily generation target, this last defined by the energy planning models. According above mentioned the dispatch of hydro generating units is a combinatorial and mixed integer non-linear programming problem whose solution can be quite complex for large hydroelectric system such as the Brazilian¿s generation system. A heuristic procedure based on Lagrangian Relaxation and Dynamic Programming is adopted as solution methodology. The approach has been tested on a hydro system composed of seventy and eight hydro plants with three hundred and ninety eight generating units of the Brazilian power generation system. The generation scheduling verified on a typical day was considered for comparison with the solution provided by the approach and the results show significant improvement in term of minimization looses and the importance of to consider the start-up and shut-down costs of hydro generating units / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

Distance relays due to their selectivity and operating speed are used in HV/EHV line protection. The dynamic nature of Mho characteristic, which happens to be most primitive technique in line protection implemented with distance relaying, is built by using the measurement of local voltage and current signals. These signals have been influenced substantially by fault resistance and the source impedance feeding the line. In case of different generation sources, the source impedance and fault characteristic also change accordingly. Environmental benefit of wind turbine technology is making it a potential source of energy. These wind turbine-generating units (WTGU) use rugged induction/synchronous machines along with power electronics converters as controlling equipment. This gives a new challenge to distance relays, as the fault current contribution of these sources depends on the converter operational principle. In this thesis a typical wind farm of Indian systems are modeled in an IN-HOUSE tool developed as part of fault analysis on wind farm system. Directly connected and front-end converter based wind turbines with their interconnections are modeled in this simulation tool. Fault voltage and current waveforms are obtained for all types of wind turbine-generating units with both radial and LILO (Loop in Loop out) connection. PSCAD based modeling has been done for DFIG type of wind turbines. The fault waveforms are generated to evaluate relay performance. Five case studies having both Radial and Loop in Loop out (LILO) connection of wind farms are simulated. These case studies generate approximately 20000 cases, which are analyzed for distance relay performance studies. In addition, the analysis is further verified on relay hardware having three characteristics, namely Self Polarized Mho (SPM), Quadrature Polarized Mho (QPM) and Quadrilateral (QUAD) characteristics. The detailed studies are carried out in this thesis to ensure and suggest the system operators with appropriate relay characteristics to be used for transmission line protection in the case of wind farms interconnected to Grid. Based on the studies carried out in the thesis, LILO connection has no impact on distance relay characteristic. In radially connected wind farms, grid side relay will operate reliably for all types of faults. It has been recommended in the thesis that wind farm side distance relay characteristics should be adjusted based on the types of wind turbines (Type-1, Type-2, Type-3 and Type-4). Based on the investigations carried out in the thesis, voltage based phase selector has been recommended for Type-4 WTGU based wind farms.

Recent decades have witnessed a significant increment in power contribution from wind generators. This increment in penetration requires power engineers to tackle multi-fold challenges concerning operational and stability aspects. There exists a significant attention among the researchers in analyzing the impact of wind generation on various system aspects. This thesis focuses on steady state voltage stability aspects with penetration of Variable speed wind generators. Traditionally, ancillary services are supplied by large conventional generators. However, with the huge penetration of wind generators as a result of the growing interest in satisfying energy requirements, and considering the benefits that they can bring along to the electrical system and to the environment, it appears reasonable to assume that ancillary services could also be provided by wind generators in an economical and efficient way. Certain types of wind generators can support reactive power for the Power Market. Fixed and Semi-Variable speed wind turbine generators were predominantly employed during the early installations of wind generators. These units require reactive power support from the grid and are usually equipped with capacitor banks to provide the necessary reactive power. Further, STATic synchronous COMpensator (STATCOM) and Static Var Compensator (SVC) with various configurations were proposed to enhance the system operations under normal and disturbed conditions. On the other hand, Variable speed wind turbine generators provide flexibility in control and hence are becoming increasingly popular. Popular among this class of wind turbine generating units are Doubly Fed Induction Generator(DFIG) and induction/synchronous Generator with Front End Converter(GFEC). Contrary to Fixed and Semi-Variable speed wind machines, Variable speed wind turbine generators are capable of providing reactive power to the grid. The converter and control schemes associated with these machines permits controlling the active and reactive power output to desired level. It is possible to control the reactive power output of these machines independently of the active power. Researchers in the past have investigated the impact of reactive power output of variable speed wind machines on system stability. In literature, approaches are proposed to utilize the flexibility in reactive power generation of DFIG to reduce system losses, improve reliability in static and dynamic system operation. Approaches in literature investigate the impact on voltage stability of system by considering the flexibility of reactive power output of wind machine in isolation. However, significant improvement in static voltage stability, voltage profile, system power losses etc. can be attained if the Reactive Power output of Variable Speed wind machines can be properly coordinated with other reactive power controllers. The prime objective of the thesis is to propose algorithms to coordinate the reactive power output of Variable Speed Wind Generators with other reactive power controllers for Enhancement in voltage stability margin, system losses and voltage profiles.