Automated fault location systems use power quality monitoring and circuit data to provide with a distance or impedance estimate to the fault. This can be used to avoid manual patrolling of the entire feeder in case of a main feeder lockout. It can also be used for circuits with repeated momentary interruptions to pinpoint the section of the circuit causing such problems. Self clearing sub cycle faults have been identified as the precursors of a number of sustained faults (requiring the operation of protective device) in utility distribution networks. The frequency of such incipient faults increases considerably as they are about to evolve into a full blown fault. This report proposes a modified and improved fault location algorithm that can be used to accurately identify sustained as well as temporary faults. The algorithm is based in the time domain and takes into account the arc voltage during a fault event. The proposed algorithm is developed, validated and applied to known distribution field data. Time domain simulation models are also used for validation purposes. The developed algorithm was observed to be very accurate when compared to other impedance based fault location algorithms proposed in the literature. Finally, sub cycle event identification and fault pre-location is proposed that can be very useful for electric utility operations. Highly accurate results were observed during this application study. For instance, a current waveform containing three incipient and one full fault event is shown in the figure given below. The estimated reactance to an incipient fault location is approximately 1.1 Ω. The fault location results obtained from the first three sub-cycle faults can be used to avert the final sustained fault event. / text

Doctor of Philosophy / Department of Electrical and Computer Engineering / Sanjoy Das and Anil Pahwa / Because a majority of day-to-day activities rely on electricity, it plays an important role in daily life. In this digital world, most of the people’s life depends on electricity. Without electricity, the flip of a switch would no longer produce instant light, television or refrigerators would be nonexistent, and hundreds of conveniences often taken for granted would be impossible. Electricity has become a basic necessity, and so any interruption in service due to disturbances in power lines causes a great inconvenience to customers. Customers and utility commissions expect a high level of reliability. Power distribution systems are geographically dispersed and exposure to environment makes them highly vulnerable part of power systems with respect to failures and interruption of service to customers. Following the restructuring and increased competition in the electric utility industry, distribution system reliability has acquired larger significance. Better understanding of causes and consequences of distribution interruptions is helpful in maintaining distribution systems, designing reliable systems, installing protection devices, and environmental issues. Various events, such as equipment failure, animal activity, tree fall, wind, and lightning, can negatively affect power distribution systems. Weather is one of the primary causes affecting distribution system reliability. Unfortunately, as weather-related outages are highly random, predicting their occurrence is an arduous task. To study the impact of weather on overhead distribution system several models, such as linear and exponential regression models, neural network model, and ensemble methods are presented in this dissertation. The models were extended to study the impact of animal activity on outages in overhead distribution system. Outage, lightning, and weather data for four different cities in Kansas of various sizes from 2005 to 2011 were provided by Westar Energy, Topeka, and state climate office at Kansas State University weather services. Models developed are applied to estimate daily outages. Performance tests shows that regression and neural network models are able to estimate outages well but failed to estimate well in lower and upper range of observed values. The introduction of committee machines inspired by the ‘divide & conquer” principle overcomes this problem. Simulation results shows that mixture of experts model is more effective followed by AdaBoost model in estimating daily outages. Similar results on performance of these models were found for animal-caused outages.

Este trabalho apresenta as principais causas de desligamento de cubículos classe 15kV, restringindo-se aos cubículos conhecidos como cabines primárias, que fazem a interface entre a rede das concessionárias de energia e os consumidores primários. Conhecidas as razões pelas quais as cabines desligam, verificou-se quais são as taxas de falha presumidas para os componentes individuais como: chaves seccionadoras e seus acessórios, disjuntores e suas bobinas, relés de proteção de sobrecorrente, transformadores de corrente e de potencial, componentes de serviços auxiliares, etc. Para avaliar a taxa de falhas das diversas configurações possíveis foram estabelecidos dezoito modelos específicos e estudadas matematicamente suas taxas de falha. Para tanto, foram utilizados os padrões estabelecidos pelas concessionárias Brasileiras como AES-ELETROPAULO, ESCELSA e CPFL, além da proposição de modelo que pode ser considerado como OTIMIZADO. Com base na experiência adquirida com os modelos estudados foi possível ainda a proposição de mecanismos de melhoria dos índices de desligamento. / This study is intended to explore the main causes of failure in 15kV switchgears, restricted to primary equipments making the interface between the Utility and the consumers. Discovering the reasons of the failures, the individual failure rates of each components was noted, as following: switches and its acessories, circuit breakers and its coils, overcurrent relays, current and voltage transformers, auxiliary circuits, etc. Analyzing the failure rates of many possible configurations of eighteen particular models, a mathematical failure rate study was achieved. A Brazilian standards, used by Energy Companies like AES-ELETROPAULO, ESCELSA and CPFL, was used to achieve the results and a optimized model could be proposed. Based on the acquired experienced during this study, it was possible to offer new techniques to decrease the failure rates.

Este trabalho apresenta as principais causas de desligamento de cubículos classe 15kV, restringindo-se aos cubículos conhecidos como cabines primárias, que fazem a interface entre a rede das concessionárias de energia e os consumidores primários. Conhecidas as razões pelas quais as cabines desligam, verificou-se quais são as taxas de falha presumidas para os componentes individuais como: chaves seccionadoras e seus acessórios, disjuntores e suas bobinas, relés de proteção de sobrecorrente, transformadores de corrente e de potencial, componentes de serviços auxiliares, etc. Para avaliar a taxa de falhas das diversas configurações possíveis foram estabelecidos dezoito modelos específicos e estudadas matematicamente suas taxas de falha. Para tanto, foram utilizados os padrões estabelecidos pelas concessionárias Brasileiras como AES-ELETROPAULO, ESCELSA e CPFL, além da proposição de modelo que pode ser considerado como OTIMIZADO. Com base na experiência adquirida com os modelos estudados foi possível ainda a proposição de mecanismos de melhoria dos índices de desligamento. / This study is intended to explore the main causes of failure in 15kV switchgears, restricted to primary equipments making the interface between the Utility and the consumers. Discovering the reasons of the failures, the individual failure rates of each components was noted, as following: switches and its acessories, circuit breakers and its coils, overcurrent relays, current and voltage transformers, auxiliary circuits, etc. Analyzing the failure rates of many possible configurations of eighteen particular models, a mathematical failure rate study was achieved. A Brazilian standards, used by Energy Companies like AES-ELETROPAULO, ESCELSA and CPFL, was used to achieve the results and a optimized model could be proposed. Based on the acquired experienced during this study, it was possible to offer new techniques to decrease the failure rates.

D.Ing. / This thesis considers water supply and divides the water supply environment into three categories; the macro water supply environment, the water supply scheme and the consumers. Each of the categories is briefly explored in terms of the factors that may influence it. Subsequently, some of the unique features of a bulk water distribution system are dealt with, as well as different approaches related to bulk water distribution system design and assessment. One of these approaches, the probabilistic approach, offers unique features to assess the reliability of a bulk water distribution system but requires that the probabilistic characteristics of the stochastic events be quantified. The above prompted the goal of this thesis; “…to assess and quantify the probabilistic characteristics of selected factors that may compromise bulk water distribution reliability”. The objectives set and dealt with in this thesis are: • Conducting a literature review that explores uncertainty, reliability, models and techniques, highlighting selected factors that may compromise bulk water distribution reliability, as well as bulk water distribution system water requirements. • Quantifying the probabilistic characteristics of water distribution pipeline failures. • Quantifying the probabilistic characteristics of pipeline failures caused by sinkholes in dolomitic areas. • Quantifying the probabilistic characteristics of power supply failures. This study provides a comprehensive summary of a range of uncertainties that may compromise bulk water distribution reliability. However, the greatest value added corresponds to the following: • It establishes a benchmark related to the probabilistic characteristics of pipeline failures for five pipeline material categories, related to pipeline failure rates and pipeline repair times. • A new methodology is developed in terms of which the probabilistic characteristics of pipeline failures caused by sinkholes in dolomitic areas can be quantified. • It provides a benchmark of the probabilistic characteristics of power supply failures at bulk water distribution pump stations. Proposals are made related to future research needs, divided into two categories: • Complementary research needs that will complement and enhance the work undertaken within this thesis. • Promotional research needs that will promote the practical application of the outcomes generated as part of this thesis.

Reliability and restoration are important considerations in electric distribution systems. Reliability analysis is generally considered as a design tool to be used to improve the performance of the system. Restoration analysis is generally considered as a tool to be used for outaged situations. Reliability and restoration analysis are related, and some of the relationships are pointed to in this work. / Ph. D.

This dissertation focuses on two specific problems related to the reliability of the modern power grid. The first part investigates the economic dispatch problem with uncertain power sources. The classic economic dispatch problem seeks generator power output levels that meet demand most efficiently; we add risk-awareness to this by explicitly modeling the uncertainty of intermittent power sources using chance-constrained optimization and incorporating the chance constraints into the standard optimal power flow framework. The result is a dispatch of power which is substantially more robust to random fluctuations with only a small increase in economic cost. Furthermore, it uses an algorithm which is only moderately slower than the conventional practice. The second part investigates “the power grid attack problem”: aiming to maximize disruption to the grid, how should an attacker distribute a budget of “damage” across the power lines? We formulate it as a continuous problem, which bypasses the combinatorial explosion of a discrete formulation and allows for interesting attacks containing lines that are only partially damaged rather than completely removed. The result of our solution to the attack problem can provide helpful information to grid planners seeking to improve the resilience of the power grid to outages and disturbances. Both parts of this dissertation include extensive experimental results on a number of cases, including many realistic large-scale instances.

This dissertation is a systematic study of the 22kV Nelson Mandela Bay Municipality (NMBM) electricity power distribution network reliability evaluation and improvements to be applied. Reliability evaluation of electric power systems has traditionally been an integral part of planning and operation. Changes in the electricity utility, coupled with aging electrical apparatus, create a need for more realistic techniques for power system reliability modelling. This work presents a reliability evaluation technique that combines set literature and evaluation criteria. In analysing system reliability, this research takes into account the reasons for many outages and voltage dips and seeks to find mitigating approaches that are financially justified. The study analyses the power system in terms of the methodology developed, using power system reliability techniques, power quality evaluation, protection analyses and evaluating the network against maintenance interventions and programs, manpower availability and weather conditions contributing to the outages. In evaluating the power system various techniques are used to determine if the power network operates within the NRS standards, namely, reliability calculations, testing of protection equipment, interrogation of power quality instruments and modeling the network on Digsilent. This study will look at all the important factors influencing power system reliability, analysing the network in terms of the methodology and recommend improvements.

Os dispositivos Indicadores de Faltas (IFs) contribuem para a melhoria do processo de localização de faltas em alimentadores de distribuição e, consequentemente, para a qualidade do fornecimento de energia elétrica. Todavia, a grande dificuldade de se aplicar tais dispositivos em larga escala está na escassez de metodologias eficientes que apontem em quais pontos do sistema de distribuição eles devem ser instalados. Por isso, o presente trabalho propõe uma abordagem computacional evolutiva capaz de alocar dispositivos IFs em alimentadores primários de distribuição de energia elétrica. De forma mais específica, o problema de se obter o melhor local de instalação é solucionado por meio da técnica de Algoritmos Genéticos (AGs), que busca obter uma configuração eficiente de instalação de IFs no tronco principal do alimentador de distribuição. A metodologia proposta é aplicada a dois alimentadores reais. Aspectos de viabilidade técnica e financeira dos IFs também são analisados. Os resultados apresentados comprovam a eficiência da metodologia proposta. / Fault Indicator (FIs) devices have contributed to improve the location of faults on primary feeders, and consequently the reliability of distribution systems. However, one of the main problems facing their installation in a large scale in a distribution system is the lack of efficient methods to analyze big networks and to pinpoint exactly on which buses these devices should be placed. Thus, this paper proposes an evolutionary computing strategy to solve the problem of fault indicator placement in primary distribution feeders. Specifically, a genetic algorithm (GA) is employed to search for an efficient configuration of FIs, located at the best positions in the main feeder. The proposed methodology was applied in two actual distribution feeders. Technical and financial viability aspects are also analyzed. Finally, the results confirm the efficiency of the GA approach to the FI placement problem.

Os dispositivos Indicadores de Faltas (IFs) contribuem para a melhoria do processo de localização de faltas em alimentadores de distribuição e, consequentemente, para a qualidade do fornecimento de energia elétrica. Todavia, a grande dificuldade de se aplicar tais dispositivos em larga escala está na escassez de metodologias eficientes que apontem em quais pontos do sistema de distribuição eles devem ser instalados. Por isso, o presente trabalho propõe uma abordagem computacional evolutiva capaz de alocar dispositivos IFs em alimentadores primários de distribuição de energia elétrica. De forma mais específica, o problema de se obter o melhor local de instalação é solucionado por meio da técnica de Algoritmos Genéticos (AGs), que busca obter uma configuração eficiente de instalação de IFs no tronco principal do alimentador de distribuição. A metodologia proposta é aplicada a dois alimentadores reais. Aspectos de viabilidade técnica e financeira dos IFs também são analisados. Os resultados apresentados comprovam a eficiência da metodologia proposta. / Fault Indicator (FIs) devices have contributed to improve the location of faults on primary feeders, and consequently the reliability of distribution systems. However, one of the main problems facing their installation in a large scale in a distribution system is the lack of efficient methods to analyze big networks and to pinpoint exactly on which buses these devices should be placed. Thus, this paper proposes an evolutionary computing strategy to solve the problem of fault indicator placement in primary distribution feeders. Specifically, a genetic algorithm (GA) is employed to search for an efficient configuration of FIs, located at the best positions in the main feeder. The proposed methodology was applied in two actual distribution feeders. Technical and financial viability aspects are also analyzed. Finally, the results confirm the efficiency of the GA approach to the FI placement problem.