This thesis presents the development of a new method for incorporating station related outages in composite or bulk system reliability analysis. Station related failures can cause multiple component outages that can propagate to other parts of the network resulting in severe damages. In order to minimize the effects of station related outages on the composite system performance it is necessary for the designer to assess their effects. This task can be achieved by including station related outages in the composite system evaluation. Monte Carlo simulation is used in this research to assess composite system reliability. The new method described in this thesis is used to include station related outages in the reliability evaluation of two composite test systems. This new method is relatively simple and can be used to consider multiple component outages due to station related failures in composite system reliability evaluation. In this approach, the effects of station related outages are combined with the connected terminal failure parameters. Reliability studies conducted on the two composite test systems demonstrates that station failures significantly affect the system performance. The system reliability can be improved by selecting appropriate station configurations. This is illustrated by application to the two composite test systems.

This thesis presents the development of a new method for incorporating station related outages in composite or bulk system reliability analysis. Station related failures can cause multiple component outages that can propagate to other parts of the network resulting in severe damages. In order to minimize the effects of station related outages on the composite system performance it is necessary for the designer to assess their effects. This task can be achieved by including station related outages in the composite system evaluation. Monte Carlo simulation is used in this research to assess composite system reliability. The new method described in this thesis is used to include station related outages in the reliability evaluation of two composite test systems. This new method is relatively simple and can be used to consider multiple component outages due to station related failures in composite system reliability evaluation. In this approach, the effects of station related outages are combined with the connected terminal failure parameters. Reliability studies conducted on the two composite test systems demonstrates that station failures significantly affect the system performance. The system reliability can be improved by selecting appropriate station configurations. This is illustrated by application to the two composite test systems.

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The reliability of supply in a bulk electricity system is directly related to the availability of the generation and transmission facilities. In a conventional vertically integrated system these facilities are usually owned and operated by a single company. In the new deregulated utility environment, these facilities could be owned and operated by a number of independent organizations. In this case, the overall system reliability is the responsibility of an independent system operator (ISO). The load point and system reliabilities are a function of the capacities and availabilities of the generation and transmission facilities and the system topology. This research examines the effect of equipment unavailability on the load point and system reliability of two test systems. The unavailabilities of specific generation and transmission facilities have major impacts on the load point and system reliabilities. These impacts are not uniform throughout the system and are highly dependent on the overall system topology and the operational philosophy of the system. Contingency evaluation is a basic planning and operating procedure and different contingencies can have quite different system and load point impacts. The risk levels associated with a given contingency cannot be estimated using deterministic criteria. The studies presented in this thesis estimate the risk associated with each case using probability techniques and rank the cases based on the predicted risk levels. This information should assist power system managers and planners to make objective decisions regarding reliability and cost. Composite system preventive maintenance scheduling is a challenging task. The functional separation of generation and transmission in the new market environment creates operational and scheduling problems related to maintenance. Maintenance schedules must be coordinated through an independent entity (ISO) to assure reliable and economical service. The methods adopted by an ISO to coordinate planned outages are normally based on traditional load flow and stability analysis and deterministic operating criteria. A new method designated as the maintenance coordination technique (MCT) is proposed in this thesis to coordinate maintenance scheduling. The research work illustrated in this thesis indicates that probabilistic criteria and techniques for composite power system analysis can be effectively utilized in both vertically integrated and deregulated utility systems. The conclusions and the techniques presented in this thesis should prove valuable to those responsible for system planning and maintenance coordination.

The reliability of supply in a bulk electricity system is directly related to the availability of the generation and transmission facilities. In a conventional vertically integrated system these facilities are usually owned and operated by a single company. In the new deregulated utility environment, these facilities could be owned and operated by a number of independent organizations. In this case, the overall system reliability is the responsibility of an independent system operator (ISO). The load point and system reliabilities are a function of the capacities and availabilities of the generation and transmission facilities and the system topology. This research examines the effect of equipment unavailability on the load point and system reliability of two test systems. The unavailabilities of specific generation and transmission facilities have major impacts on the load point and system reliabilities. These impacts are not uniform throughout the system and are highly dependent on the overall system topology and the operational philosophy of the system. Contingency evaluation is a basic planning and operating procedure and different contingencies can have quite different system and load point impacts. The risk levels associated with a given contingency cannot be estimated using deterministic criteria. The studies presented in this thesis estimate the risk associated with each case using probability techniques and rank the cases based on the predicted risk levels. This information should assist power system managers and planners to make objective decisions regarding reliability and cost. Composite system preventive maintenance scheduling is a challenging task. The functional separation of generation and transmission in the new market environment creates operational and scheduling problems related to maintenance. Maintenance schedules must be coordinated through an independent entity (ISO) to assure reliable and economical service. The methods adopted by an ISO to coordinate planned outages are normally based on traditional load flow and stability analysis and deterministic operating criteria. A new method designated as the maintenance coordination technique (MCT) is proposed in this thesis to coordinate maintenance scheduling. The research work illustrated in this thesis indicates that probabilistic criteria and techniques for composite power system analysis can be effectively utilized in both vertically integrated and deregulated utility systems. The conclusions and the techniques presented in this thesis should prove valuable to those responsible for system planning and maintenance coordination.

The basic function of an electric power system is to supply its customers with electric energy as economically as possible and with a reasonable degree of continuity and quality. Power system reliability evaluation techniques are now highly developed through the work of many researchers and engineers. It is expected that the application of power system reliability evaluation in bulk power systems will continue to increase in the future especially in the newly deregulated power industry. This thesis presents research conducted on the three areas of incorporating multi-state generating unit models, evaluating system performance indices and identifying transmission deficiencies in composite system adequacy assessment. The research was done using a previously developed software package designated as MECORE. Many generating companies in both the traditionally regulated and newly deregulated electrical power industry have large generating units that can operate in one or more derated states. In this research work, load point and system reliability indices are evaluated using two-state and multi-state generating unit models to examine the impact of incorporating multi-state generating unit models in composite system adequacy assessment. The intention behind deregulation in the power industry is to increase competition in order to obtain better service quality and lower production costs. This research illustrates how Canadian power systems have performed in the past using data compiled by the Canadian Electricity Association. A procedure to predict similar indices is presented and used to estimate future performance and the effects of system modifications. The incentives for market participants to invest in new generation and transmission facilities are highly influenced by the market risk in a deregulation environment. An adequate transmission system is a key element in a dynamic competitive market. This thesis presents a procedure to identify transmission deficiencies in composite generation and transmission system. The research work illustrated in this thesis is focused on the application of probabilistic techniques in composite system adequacy assessment and particularly in the newly deregulated electric power industry. The conclusions and the techniques presented should prove valuable to those responsible for power system planning.

The basic function of an electric power system is to supply its customers with electric energy as economically as possible and with a reasonable degree of continuity and quality. Power system reliability evaluation techniques are now highly developed through the work of many researchers and engineers. It is expected that the application of power system reliability evaluation in bulk power systems will continue to increase in the future especially in the newly deregulated power industry. This thesis presents research conducted on the three areas of incorporating multi-state generating unit models, evaluating system performance indices and identifying transmission deficiencies in composite system adequacy assessment. The research was done using a previously developed software package designated as MECORE. Many generating companies in both the traditionally regulated and newly deregulated electrical power industry have large generating units that can operate in one or more derated states. In this research work, load point and system reliability indices are evaluated using two-state and multi-state generating unit models to examine the impact of incorporating multi-state generating unit models in composite system adequacy assessment. The intention behind deregulation in the power industry is to increase competition in order to obtain better service quality and lower production costs. This research illustrates how Canadian power systems have performed in the past using data compiled by the Canadian Electricity Association. A procedure to predict similar indices is presented and used to estimate future performance and the effects of system modifications. The incentives for market participants to invest in new generation and transmission facilities are highly influenced by the market risk in a deregulation environment. An adequate transmission system is a key element in a dynamic competitive market. This thesis presents a procedure to identify transmission deficiencies in composite generation and transmission system. The research work illustrated in this thesis is focused on the application of probabilistic techniques in composite system adequacy assessment and particularly in the newly deregulated electric power industry. The conclusions and the techniques presented should prove valuable to those responsible for power system planning.

This master’s thesis applies dielectric relaxation spectroscopy to analyse impact of climatic changes on dielectric properties of composite material samples (TSA 220S varnish combined with 60.030 mica). Experiments aim to analyse effect of mica composite mass ratio (0, 4, 8 and 16 % of mica), relative humidity (0, 33, 55, 65, 75 and 95 %) and temperature (23, 30, 40 and 50 C) on complex permitivity as a function of frequency.

Diffusion Magnetic Resonance Imaging (DMRI) is a class of Magnetic Resonance Imaging (MRI) techniques with broad medical applications ranging from characterization of tumors and brain damage to potential prediction of stroke. Gradient coil and signal-to- noise ratio (SNR) constraints limit spatial resolution, accuracy, and scan time in DMRI. Achieving high b-values (measures of a scan's sensitivity to diffusion) often require scans with long diffusion gradient pulses, leading to significant magnetic resonance (MR) signal decay before the signal can be sampled. This signal loss reduces the accuracy of diffusion parameter estimation. The ability to sample the MR signal sooner while maintaining the same b-value is restricted by the maximum amplitude and slew rate of gradient coils. A composite system utilizing body and high-powered insert gradient coils can achieve high b-values more quickly, enabling a shorter delay between excitation and signal sampling and improved accuracy of diffusion parameter estimation. Alternately, such a system can achieve higher b-values at an equivalent delay between excitation and signal sampling. This thesis describes the implementation of such a system, experiment design for evaluating the benefits of the system to DMRI, and design of a diffusion phantom. Also included are a characterization of a composite system's improvements to DMRI based on analysis of experimentally-obtained data and simulation results validating those findings. Finally, recommendations for further improvements to diffusion MRI are given.

[pt] Este trabalho apresenta uma nova metodologia para a avaliação de índices de confiabilidade para sistemas compostos de geração e transmissão. Através, deste novo método é possível obter uma estimativa precisa do valor da confiabilidade em sistemas de potência. A flexibilidade na modelagem e a eficiência da simulação são características básicas da metodologia proposta. Além disto, é introduzido um novo índice de confiabilidade custo esperado da perda de carga (LOLC - loss of load cost) que fornece todas as informações necessárias sobre os impactos econômicos das interrupções no fornecimento para os consumidores. Com este objetivo foi desenvolvido um novo modelo de simulação, denominado pseudo-seqüencial, que realiza sorteios não-sequenciais para determinar os estados de falha, e simulações cronológicas apenas para as subseqüência de falha. Nos exemplos com os sistemas IEEE- MRTS e Sudeste brasileiro, a simulação pseudo- seqüencial mostrou-se cerca de 25 a30 vezes mais rápida que a simulação convencional, baseada na precisão da estimativa do índice LOLC. Para melhorar ainda mais a eficiência do novo método é investigada a aplicação de uma técnica de redução de variância denominada amostragem por importância. Os resultados comprovam a possibilidade de aumentar a eficácia através da utilização de estratégias simples para os sorteios. Outros aspectos importantes associados com o valor da confiabilidade também podem ser analisados com a simulação pseudo-seqüencial : distribuições do custo de interrupção no sistema, curva de carga cronológica anual; consideração de incertezas na carga; representação da manutenção programada; utilização de funções não-exponenciais. Uma outra alternativa para a determinação do valor da confiabilidade é a simulação pseudo-seqüencial markoviana. Nesta abordagem o sistema é modelado por um processo de Markov homogêneo e o método de transição de estados é utilizado para a identificação das interrupções. Algumas das flexibilidades de representação e a precisão do método pseudo-seqüencial original são mantidas. Finalmente, um esquema de redução de variância especialmente desenvolvido para a simulação pseudo-seqüencial é testado em sistemas equivalentes. / [en] This work presents a new methodology to evaluate reliability índices in composite generation and transmission systems. Through this new approach is possible to achieve an accurate estimate of the reliability worth of power systems. The modeling flexibility and simulation efficiency are basic features of the proposed approach. Moreover, it is introduced a new reliability index called LOLC (loss of load cost), which provides a complete information about the economic impact of customer supply interruptions. Bearing in mind this objective was developed a new developed a new simulation model, named pseudo-sequential, based on the nonsequencial sampling to locate the failed states and on the chronological simulation of only the sub- sequences associated with these failed states. In case studies with the IEEE Modified Reliability Test System (MRST) and the Brazilian southeastern system, the pseudo- sequential simulation has shown about twenty-five to thirty times faster than the convential sequential Monte Carlo simulation, based on the relative uncertainly of LOLC estimate. In order to improve the efficacy of the new approach, it is examined the application of one variance reduction technique named importance sampling. The results prove the ability of increasing the speedup through trivial sampling strategies. Another alternative to asses the reliability worth is markovian pseudo-sequential simulation. In this approach, the system is modeled by a homogeneus. Markov process and the state transition method is applied to establish the supply interruptions. The flexibility and accuracy of the original pseudo-sequential method are partially retained. Finally, it is used a customized variance reduction scheme to test pseudo-sequential simulation in equivalent systems.