Dans cette thèse, nous traitons la question de la fiabilité du système électrique et notamment le problème d’adéquation des capacités de production d’électricité avec une demande future, qui évolue d’une façon hautement imprévisible. Cette question suscite actuellement des débats économiques et politiques au sein de la commission européenne de l’énergie. Elle s'inscrit dans le contexte de déréglementation et de réformes de libéralisation opérées aux seins de pays occidentaux. Les défaillances qui se sont accompagnées avec cette déréglementation et qui ont provoqué diverses crises ont pour origine l’aversion aux risques des investisseurs, l’incertitude sur la demande future et les prix du carburants et le pouvoir de marché exercé pour les producteurs existants particulièrement en période de tension. Ceci a provoqué d’une part, des prix d’électricité hautement aléatoires et élevés et d’autre part, un manque d’incitations aux nouveaux investissements. Pour y faire face, plusieurs mécanismes additionnels assurant une incitation adéquate aux investissements et une maîtrise des prix d’électricité ont été proposés. Dans ce travail, on compare l’efficacité relative des mécanismes marchands d’incitation aux investissements. L’adéquation des capacités de production dans le long terme constitue le principal critère d’évaluation de ces mécanismes. Par ailleurs l’efficacité en termes de coût et de réduction des manipulations des prix dans les marchés forment deux éléments importants à prendre en considération lors de leur évaluation. Dans la littérature, ces mécanismes ont été traités d’un point de vue purement qualitatif, ce qui limite les enseignements qu’on peut tirer sur l’efficacité de chacun. L'apport de ce travail est de proposer une analyse conduite dans le cadre d'un modèle dynamique numérique. La dimension concurrentielle est prise en compte en mobilisant la théorie des jeux. La résolution du modèle fait appel à la méthode de la programmation dynamique et aux méthodes de problème de complémentarité et de l’inégalité variationnelle. En complément à l'analyse théorique, une étude expérimentale est conduite afin d'intégrer une plus grande diversité de stratégie. Nous concluons de ces recherches que la mise en place d’un mécanisme marchand d’incitation aux investissements est prometteuse. Il permet d’assurer l‘adéquation future du système électrique à faible coût et de lutter efficacement contre le problème de pouvoir de marché. / In this thesis, we deal with the question of reliability of electricity system and particularly the problem of generation capacity adequacy in electricity markets, characterized by uncertain and volatile demand. This question is currently the object of many politics and economics debates in the European Commission of energy. It occurs within the context of deregulations and reforms of liberalization operated in western countries. This deregulation was caused many shortages and crisis in many electricity markets in the world. Failures are caused by several factors such as, the presence of uncertainties on future demand and fuel prices, the risk-averse behavior of investors and the market power exercised by existing generators. They had lead to high spot market prices and a fundamental imbalance between the steadily growing demand for power and the limited increases, due to the lack of investments, in generation capacities. Many mechanisms, additional to the energy market, that ensure an adequate incentive for investments and a stable and socially acceptable electricity prices have been proposed. In this work, we compare different investment incentive mechanisms, in terms of long-term capacity adequacy in an uncertain environment, cost effectiveness and the ability of reducing market power. In the literature, the problem of long-term system reliability has been largely studied in qualitative terms. A few works attempt to model the quantitative effects of those market designs. The contribution of this work is to propose a quantitative analysis based on dynamics models. Competition is considered by using the principles of game theory. Stochastic dynamic programming is used to deal with the stochastic environment of the market and mixed complementarity problem and variational inequality formulations are employed to find Nash equilibrium. In addition to the analytic analysis, an experimental study is carried out in order to include a larger diversity of strategy. The main finding of this thesis is that market-based mechanisms would be the most cost-efficient mechanisms for assuring long-term system adequacy, encouraging earlier and adequate new investments in the system and for reducing market power.

No description available.

The reliability of structures subjected to time-invariant or time-variant random loads is considered herein. This is an important field of engineering, as it provides the framework for assessing whether newly designed or existing structural systems meet their design requirements in a given lifetime, or whether they experience what is termed “structural failure”. An important aspect of reliability analysis is the study of structures subjected to multiple time-varying loads. For this class of systems, it is well-known that by modelling the loads as (time-variant) random processes, the reliability may be evaluated by considering the outcrossing of a vector process out of a safe domain. However, due to the possibility that the loads may not be fully-dependent, all loads may not necessarily contribute to structural failure. To account for this the treatment of vector-outcrossings may need to allow for the possibility of outcrossings being caused by individual loads, as distinct from combinations of all loads. The procedure used to analyse combinations of loads depends on the stochastic process model used to represent the loads. Two well-known load models have been presented in the literature—they are referred to herein as the ‘on-off’ model and the ‘standard’ model. The ‘on-off’ model typically assumes loads are non-negative, and are either ‘on’ (eg their value is non-zero) or ‘off’ (eg their value is strictly zero). They can contribute to failure only when they are ‘on’. This model is represented by a somewhat artificial ‘composite’ probability distribution, obtained by modifying the original load probability density function (pdf) so that a ‘finite’ non-zero probability represents explicitly the possibility that the load is ‘off’. To implement this model in time-variant analysis, it is necessary to consider all possible combinations of loads being ‘on’ and ‘off’. In contrast, the ‘standard’ model (which is the more commonly used) typically allows loads to be negative; it is also typically represented solely by the original load pdf, and therefore effectively assumes each load is always ‘on’. To allow for the possibility of one or more loads not to cause failure, herein the value of such loads is held ‘constant’ at the time of failure, when the value of all loads actually causing failure is allowed to change. Use of the ‘standard’ model is examined herein. The “Directional Simulation in the Load Space (DS-LS)” approach is a tool used to perform reliability analysis. It is particularly suitable for time-variant analysis, as it allows loads to be represented as random processes, and to be modelled properly. DS-LS has so far been shown to work well for relatively simple structures subjected to one or more time-invariant random loads, and has been used to examine vector outcrossings in systems comprising either discrete or continuous loads. To enable the proper consideration of load combinations, and to provide some improvements in the formulation of the technique, a generalisation of the DS-LS approach is proposed herein. The generalisation is achieved in two stages. The first involves modifying the time-invariant and time-variant DS-LS formulation to allow for the possibility of positioning the origin of DS-LS not only in the ‘safe’ region of the load space (which the formulation currently requires) but in the ‘failure’ region, or even ‘exactly’ on the boundary separating the safe and failure regions. The modifications are necessary because for even simple structures, the ‘exact’ location of the safe and failure region is not always known explicitly ‘a priori’. The second involves developing the time-variant DS-LS formulation to consider explicitly outcrossings caused by combinations of one or more loads, during analysis of systems comprising stationary continuous gaussian loads. To do this, the direction of the load process vector is ‘fixed’ at each point of outcrossing, to physically represent the particular combination of loads causing the outcrossing. By considering each possible load combination, all loads not causing an outcrossing are then held constant during radial integration, thereby modelling those that do not contribute to each outcrossing. The proposed formulation differs from most load combination analysis techniques (which, evidently, simplify the analysis) as it is analytically ‘exact’, and it considers explicitly all possible combinations of loads. The concepts and formulations proposed herein may provide further understanding of reliability analysis performed by DS-LS (or other techniques) and may aid their future development. / PhD Doctorate

<p>In many parts of the tropics irregular and erratic rainfall has great national economic as well as socio-economic effects. In Kenya, where a large part of the population live in rural areas and rainfed agriculture is the main livelihood, droughts and floods have farreaching impacts on communities. One form of mitigating the negative effects of drought is the implementation of simple, small-scale, low cost schemes called rainwater harvesting. This involves the capture, storing and redirection of rainfall, runoff, and groundwater. In Kenya, such schemes are being implemented in rural areas through different actors. Two Non-Governmental Organizations involved are the Kenya Rainwater Association and the German Agro Action that work in Tseikuru, a semi-arid area with water availability and sanitation issues. The main livelihood is agropastorialism and there is little experience with rainwater harvesting. Commonly, water is collected by digging shallow holes into dry river beds where groundwater tables are high. These areas are prone to contamination and could be situated many kilometres away, making water collection laborious. By implementing rainwater harvesting schemes water availability as well as water quality is expected to be improved. However, due to great rainfall variability and effects of climate change these schemes may fall short of their expectations. Also the potential change on water demand may affect communities’ response to prolonged dry spells. This study aims to examine whether the implemented rainwater harvesting schemes in rural Tseikuru are reliable in times of adverse rainfall and if increased water availability (and potentially also increased water demand) affects the communities’ vulnerability towards droughts. The study is based on interviews with local stakeholders and technicians during a Minor Field Study in Tseikuru, as well as statistical analysis on rainfall data over the area and literature studies. Results showed that rainwater harvesting schemes are generally successful in supplying readily available and safe water. However the rural population of Tseikuru have not completely abandoned their old habits of collecting water from dry riverbeds, choosing instead to treat the schemes as an alternative source to water, thereby avoiding dependency towards the schemes.</p>

<p>Did the right person win? In competitive sports the difference between winning and loosing can be very marginal but still the result will have a big impact. To finish second, even if it is an Olympic Game, can be felt like a failure for the athlete. In the light of this the quality of the measurements and the judgements in sports are an extremely important issue. In this dissertation, consisting of two separate reports and one summary report, the freestyle discipline, acroski, and the gymnastic discipline, rhythmic gymnastics (RG) where studied with a focus on the rules and judgements in the sports. The reliability and validity of the rule and judging systems were analysed together with changes in the rule and judging systems. The reliability, as the judges ability to interpret the rules and judge in a consistent way, and validity in the sense that the judgements, and the rules for the judgements, where in accordance with the idea of the sport. Information was gathered from rulebooks, judging manuals, meeting protocols, and historical documents. For information on how the rules and judgements where perceived among people involved in the two sports, interviews where carried out with two coaches, two judges and four athletes from each of the sports. In the summary report the results from the two reports where discussed and a comparison of the rule systems and judgements was made together with a discussion about reliability and validity problems in sports measured by time, length and height. The results showed that the rule and judging systems in acroski and RG in a short time have gone through major changes to increase the reliability and validity in the judgements. The quick evolution of these sports seems to be the main reason for these changes but also other factors where of vital importance. Finding the balance between making the judgements as objective as possible, without loosing the idea of the sport, together with the quick evolution of the sports, seemed to be the main challenges in the rule and judging systems of acroski and RG.</p>

<p><strong>Bakgrund</strong>: Det finns i nuläget inget svenskt self-efficacy instrument för barn och ungdomar med smärta. Den här undersökningen syftade till att översätta samt reliabilitets- och validitetstesta en engelskspråkig self-efficacy skala för barn och ungdomar med smärta.</p><p><strong>Metod</strong>: Urvalet bestod av 62 elever från tre olika klasser i Uppsala. Skalan översattes till svenska och ett frågeformulär utformades för att möjliggöra en utvärdering av test-retest reliabilitet samt kriterie- och ögonblicksvaliditet.</p><p><strong>Resultat</strong>: Värdena på viktad kappa för överensstämmelsen av två skattningar (S1 och S2) med self-efficacy instrumentet (SEIS) varierade mellan <em>K_w</em>₌0,37 -  <em>K_w</em>₌0,75. Sambandet mellan Functional disability inventory (FDI) och SEIS beräknades med Spearmans rangkorrelation där <em>r_s</em> = 0,364 (p<0,05). Ögonblicksvaliditeten för SEIS beskrevs som att den var lättförståelig, innehöll vardagliga aktiviteter men att vissa aktiviteter saknades.</p><p><strong>Konklusion</strong>: Slutsatsen av denna undersökning var att frågorna i SEIS bör omarbetas för att bli mer specifika och kunna användas. Det kan även utarbetas nya aktiviteter till instrumentet eftersom resultaten av undersökningen visade att vissa aktiviteter saknades. På grund av urvalets karaktär var resultaten troligtvis inte generaliserbara.</p>

The purpose of this study is to develop accuracy enhancement techniques for the Time Domain Reflection/Transmission (TDR/T) measurements including the analysis of the error sources for the Enhanced Accuracy TDR/T (EA-TDR/T). These TDR/T techniques are used for IC and IC package interconnect characterization and equivalent circuit model extraction, which are important for evaluating the overall system performance in today's digital IC design. The frequency domain error correction has been used to get parameters for a Device Under Test (DUT) from time domain measurements. The same technique can be used as an intermediate step for obtaining the EA-TDR/T. Careful choice of the acquisition window and precise alignment of the DUT and calibration standard waveforms are necessary to get the accuracy enhancement for the TDR/T. Improved FFT techniques are used in order to recover the actual spectra of the step-like time domain waveforms acquired with an acquisition window with a finite time length. The EA-TDR/T waveform are recovered from error corrected frequency domain parameters of the DUT by launching an ideal excitation at the DUT and finding the response. The rise time of the ideal excitation can be faster than that of the physical excitation in the measurement system. However, excessive high-frequency noise can enter the system if the rise time of the ideal excitation is chosen to be too high. The resulting EA-TDR/T waveforms show significantly less aberrations than the conventional TDR/T waveforms, hence allow us to extract accurate equivalent circuit model for the DUT, which in our case is IC interconnects. / Graduation date: 1995

Graduation date: 1994

Modern power systems are now stepping into the post-restructuring era, in which utility industries as well as ISOs (Independent System Operators) are involved. Attention needs to be paid to the reliability study of power systems by both the utility companies and the ISOs. An uninterrupted and high quality power is required for the sustainable development of a technological society. Power system blackouts generally result from cascading outages. Protection system hidden failures remain dormant when everything is normal and are exposed as a result of other system disturbances. This dissertation provides new methods for power system vulnerability analysis including protection failures. Both adequacy and security aspects are included. The power system vulnerability analysis covers the following issues: 1) Protection system failure analysis and modeling based on protection failure features; 2) New methodology for reliability evaluation to incorporate protection system failure modes; and, 3) Application of variance reduction techniques and evaluation. A new model of current-carrying component paired with its associated protection system has been proposed. The model differentiates two protection failure modes, and it is the foundation of the proposed research. Detailed stochastic features of system contingencies and corresponding responses are considered. Both adequacy and security reliability indices are computed. Moreover, a new reliability index ISV (Integrated System Vulnerability) is introduced to represent the integrated reliability performance with consideration of protection system failures. According to these indices, we can locate the weakest point or link in a power system. The whole analysis procedure is based on a non-sequential Monte Carlo simulation method. In reliability analysis, especially with Monte Carlo simulation, computation time is a function not only of a large number of simulations, but also time-consuming system state evaluation, such as OPF (Optimal Power Flow) and stability assessment. Theoretical and practical analysis is conducted for the application of variance reduction techniques. The dissertation also proposes a comprehensive approach for a TTC (Total Transfer Capability) calculation with consideration of thermal, voltage and transient stability limits. Both steady state and dynamic security assessments are included in the process of obtaining total transfer capability. Particularly, the effect of FACTS (Flexible AC Transmission Systems) devices on TTC is examined. FACTS devices have been shown to have both positive and negative effects on system stability depending on their location. Furthermore, this dissertation proposes a probabilistic method which gives a new framework for analyzing total transfer capability with actual operational conditions.

Management decisions in complex industrial facilities usually consider both the economic and environmental aspects of the plant's performance. For nuclear power plants (NPPs), safety is also a very substantial issue. The objectives of this dissertation are to develop and demonstrate a novel useful conceptual model that could be used to allocate maintenance funds for a nuclear power plant in such a way as to meet all specified safety requirements and objectives, while achieving a high degree of economic performance. The model is based on the general theory that the reliability of a plant at any time is a function of its initial reliability and the maintenance history of the individual plant components (Smith, 1997). Such a model can assist in evaluating strategic management decisions regarding allocation of funds for nuclear power plant maintenance. It could be used as a simulation tool; various scenarios could be studied to answer "what if" questions. Simulations of this type will allow a better understanding of the relationship between maintenance, economic performance, and safety, and consequently will lead to better decision making. The novelty of this model is tied to the intimate relationship that it develops between maintenance activities at a nuclear plant, and their relationship to prescribed safety requirements and to the economic performance of that plant.