Extra High Voltage (EHV) transmission corridor siting studies are complex and costly procedures, which are often prolonged by technical, public, institutional, and state regulatory factors. The primary goal of this research is to contribute to a more predictable and expedient siting study. The following objectives are accomplished: - Exploration and description of technical and methodological aspects of siting in terms of the general approach to the siting study, impact assessment techniques, data collection and mapping considerations. - Exploration and description of the following public and institutional considerations in the siting study: public participation, active opposition, media coverage, attitudes of affected agencies, and communication among involved organizations. Determination of the effects of these considerations on the siting process. - Review and evaluation of the state siting regulations in terms of: clarity of requirements, technical siting requirements, coordination of actions in the study, coordination with other relevant regulations, and public and agency participation in the study. Identification of the effects of the state regulations on the siting study process. - Development of guidelines for improved EHV transmission corridor siting studies. The principal methodology of the research is the single case study of Wyoming-Cloverdale 765 kV siting project, which represents a model of a contemporary, interstate, EHV siting study. The results of the case study are complemented by the review of state siting regulations and the literature. The major outcome of the research are the guidelines for improved corridor siting studies. The guidelines are developed for corridor siting study consultants, electric utility companies, and state regulatory commissions. Findings of the research indicate that technical, public, institutional, and state regulatory factors interactively affect the process of the corridor siting study. Furthermore, the siting study has dominant political overtones, and as such cannot be treated as a merely technical project. Public opposition to new EHV transmission lines can significantly increase the effects of technical, public, institutional, and regulatory deficiencies, reducing the probability of line approval. The testing of the guidelines in siting study practice, and a multiple case study research dealing with the same considerations and their interactions, are suggested for future research. / Ph. D.

DC power distribution has gained popularity in sustainable buildings, renewable energy utilization, transportation electrification and high-efficiency data centers. This dissertation focuses on two aspects of facilitating the application of dc systems: (a) system-level control to improve load sharing, voltage regulation and efficiency; (b) design of a high-efficiency interface converter to connect dc microgrids with the existing low-voltage ac distributions, with a special focus on common-mode (CM) voltage attenuation. Droop control has been used in dc microgrids to share loads among multiple sources. However, line resistance and sensor discrepancy deteriorate the performance. The quantitative relation between the droop voltage range and the load sharing accuracy is derived to help create droop design guidelines. DC system designers can use the guidelines to choose the minimum droop voltage range and guarantee that the sharing error is within a defined range even under the worst cases. A nonlinear droop method is proposed to improve the performance of droop control. The droop resistance is a function of the output current and increases when the output current increases. Experiments demonstrate that the nonlinear droop achieves better load sharing under heavy load and tighter bus voltage regulation. The control needs only local information, so the advantages of droop control are preserved. The output impedances of the droop-controlled power converters are also modeled and measured for the system stability analysis. Communication-based control is developed to further improve the performance of dc microgrids. A generic dc microgrid is modeled and the static power flow is solved. A secondary control system is presented to achieve the benefits of restored bus voltage, enhanced load sharing and high system efficiency. The considered method only needs the information from its adjacent node; hence system expendability is guaranteed. A high-efficiency two-stage single-phase ac-dc converter is designed to connect a 380 V bipolar dc microgrid with a 240 V split-phase single-phase ac system. The converter efficiencies using different two-level and three-level topologies with state-of-the-art semiconductor devices are compared, based on which a two-level interleaved topology using silicon carbide (SiC) MOSFETs is chosen. The volt-second applied on each inductive component is analyzed and the interleaving angles are optimized. A 10 kW converter prototype is built and achieves an efficiency higher than 97% for the first time. An active CM duty cycle injection method is proposed to control the dc and low-frequency CM voltage for grounded systems interconnected with power converters. Experiments with resistive and constant power loads in rectification and regeneration modes validate the performance and stability of the control method. The dc bus voltages are rendered symmetric with respect to ground, and the leakage current is reduced. The control method is generalized to three-phase ac-dc converters for larger power systems. / Ph. D.

The thesis addresses electronic power distribution systems for the residential applications. Presented are both, renewable energy ac-nanogrid system along with the vehicle-to-grid technology implementation, and envisioned structure and operation of dc-nanogrid addressing all system components chosen as an inherent part of the future electrical architecture. The large-scale model is built and tested in the laboratory environment covering a few operational modes of the ac-nanogrid, while later in the thesis is shown how dc bus signaling technique could be contemplated for the energy management of the renewable energy sources and their maximal utilization. Thesis however puts more focus on the dc-nanogrid system to explore its benefits and advantages for the electrical systems of the future homes that can easily impact not only residential, but also microgrid, grid and intergrid levels. Thus, presented is low frequency terminal behavioral modeling of the system components in dc-nanogrid motivated by the fact that system engineers working on the system-level design rarely have access to all the information required to model converters and system components, other than specification and data given in the datasheets. Using terminal behavioral modeling, converters are measured on-line and their low frequency dynamics is identified by the means of the four transfer functions characteristically used in two port network models. This approach could significantly improve system-level design and simulations. In addition to previously mentioned, thesis addresses terminal behavioral modeling of dc-dc converters with non-linear static behavior showing hybrid behavioral models based on the Hammerstein approach. / Master of Science

Demand Side Management (DSM) has begun to emerge as a major component of utility planning, with more utilities than ever before using it to help meet their own needs and those of their customers. DSM encompasses utility and customer activities aimed at modifying load shape, which embodies the timing and level of customer electricity demand. Future load shapes will result from the combined effect of individual DSM programs seeking specific load shape objectives. Load Duration Curve (LDC) is the vehicle through which DSM impacts are incorporated into power system planning and operation. Models of the LDC is one of the most important tools in the analysis of electric power system. The DSM will affect the peak load, the base load and total energy demand of the load duration curve. Those three impacts have to be explicitly modeled into the load duration curve for properly representing the effects of demand side management activities. However, the available models cannot properly represent the impacts of demand side management into load duration curve, because they do not explicitly model those three variables into their load duration curve. A new model that can incorporate the effects of demand side management is needed by utilities to help them with planning and operation. A new way to directly model the inverted load duration curve (ILDC) is presented in this study thus facilitating the representation of DSM impacts. Peak Load, base load and total energy demand are the variables of the new model. Using DSM activities as case studies, the new model produced good results compared to other widely used models, in term of reliability indices (LOLP and ENS) and total energy under the load duration curve. The flexibility, simplicity and the speed of execution of the new model in calculating the reliability indices are demonstrated. The capability of the new model to calculate the capacity credit is also presented. As a result of its ability to represent energy under load duration curve, the new model is inserted into WASP computer program to calculate the production cost. Results obtained from the new model (modified WASP) compared to results from original WASP are very close. Based on these capabilities it can be claimed that the new ILDC model is a better overall model and can be used as an alternative load model in utility planning and operation. / Ph. D.

Electric utilities are constantly seeking ways to reduce costs, and one way is to defer the construction of major new facilities. Such a deferal can be instituted by automating the power distribution system in an effort to make the system operate more efficiently and effectively. Increased efficiency on the distribution level improves the use of existing facilities on the distribution, transmission, and generation levels. The stumbling block for justifying distribution automation is often at the economic evaluation stage. This is due to the difficulty of incorporating the effects of technologies which have not been implemented in the past. In this research, a new method of economic analysis of utility distribution systems is proposed. The method will utilize interval analysis to determine the effects of uncertainty in data in utility revenue requirement studies. One of the frequently encountered problems in applying interval analysis is the resulting overly large bounds which in turn reduce the usefulness of results. Therefore, a method of obtaining sharp bounds is presented. The economic calculations will incorporate results from reliability analysis as well as reconfiguration studies. Thus, an explicit consideration of engineering design aspects is included. In addition, a cost/effectiveness analysis of distribution automation is presented in terms of several proposed economic indices associated with system cost, reliability, efficiency, and peak. A method of incorporating value of service considerations into revenue requirement studies is also presented. The capability to analyze automation expansion plans as well as conventional expansion plans will be discussed. Accordingly, utility distribution planning can be more precise with regard to potential economic benefits. / Ph. D.

No description available.

Este trabalho apresenta uma análise dos surtos em redes aéreas secundárias de distribuição causados por descargas atmosféricas diretas no circuito primário. Alguns trabalhos publicados sobre o fenômeno são comentados, sendo também analisados vários outros estudos relativos à modelagem de componentes. No trabalho, os principais componentes da rede foram modelados e incluídos na representação de uma topologia típica (com as linhas primária e secundária). Assim, foram considerados: transformador de distribuição, isoladores, pára-raios, cargas (consumidores) e resistências de aterramento. Os modelos foram validados, quando possível, através de ensaios em laboratório. Algumas alternativas de proteção da rede secundária foram consideradas. Foi verificada a influência de alguns parâmetros relevantes tais como amplitude e tempo de frente da corrente da descarga, resistências de aterramento, modelos de cargas e posição da descarga. Os resultados foram obtidos por simulações computacionais realizadas através do programa ATP (Alternative Transients Program). São apresentadas formas de onda de sobretensões nos consumidores. Também são apresentados e discutidos valores de corrente e energia nos dispositivos de proteção, fornecendo informações sobre as alternativas de proteção. / This work presents an evaluation of surges in low-voltage overhead distribution lines caused by direct lightning strikes in medium voltage lines. Some publications concerning the phenomenon are commented and several other studies used during the process of modeling of the components are also analysed. The main components of the distribution system were modeled and included. So, a typical distribution network topology (with the primary and secondary lines) was represented including its components: distribution transformer, insulators, surge arresters, loads and ground resistances. The performance of the developed models, whenever possible, was verified by laboratory tests. Some possibilities of the secondary protection were included. Parameters having major effect on the results, such as the lightning current amplitude and front time, the values of grounding resistances, the models of the loads and the lightning strike position were taken into consideration in the study. The results were obtained by simulations performed using the ATP (Alternative Transients Program). Waveforms are presented in order to provide information on the characteristics of the overvoltages in the consumers along the line. Currents, as well as energy absorbed by the low-voltage surge arresters are aldo presented and discussed, providing useful information about the performance of some protection alternatives.

Este trabalho apresenta um estudo de caracterização das impedâncias de entrada, em função da frequência, de instalações residenciais de baixa tensão e diversos equipamentos eletro-eletrônicos comumente encontrados. As respostas em frequência medidas são ajustadas e modeladas por redes RLC simples, mas efetivas, que podem ser utilizadas em qualquer programa computacional para simulações de transitórios. A faixa de frequências, até 5 MHz, permite o uso desses modelos em estudos associados a transitórios atmosféricos ou causados por chaveamentos. É importante ressaltar a existência de muito poucos trabalhos nesse assunto, pois, usualmente, as instalações de baixa tensão, ou os equipamentos conectados, são representadas por simples elementos concentrados, resistores, indutores ou capacitores. Por outro lado, sabe-se que os níveis de sobretensões em um sistema, ou instalação, são fortemente dependentes das cargas conectadas e, quanto mais precisos os modelos, melhores e mais confiáveis simulações são obtidas. Este trabalho inclui simulações com o programa computacional ATP utilizando os modelos desenvolvidos para avaliação de surtos em uma rede de distribuição típica submetida a descargas atmosféricas diretas no circuito primário. Além disso, utilizando o programa Pspice, são realizadas simulações da resposta interna de uma instalação residencial, com diversos equipamentos conectados, e submetida a surtos atmosféricos em sua entrada. O trabalho concentra informações práticas e úteis sobre estudos de surtos em sistemas e instalações de baixa tensão / This work presents a study of impedance characteristics, over a wide range of frequencies, of residential low-voltage installations and electric-electronic appliances, commonly found in residential installations. The measured frequency responses are fitted and modeled by simple, but effective, RLC networks, that can be used in any software for transient simulations. The range of frequencies, up to 5 MHz, allows the use of these models considering lightning or switching studies. It is of importance to point the lack of publications focusing this topic, because usually the low-voltage installations, or connected equipment, are represented by simple lumped components inductances, resistances or capacitances. Otherwise, it is well known that the overvoltage level of a system, or installation, is strongly dependent on the connected loads and for more precise models, better and more reliable simulation results are obtained. This work includes ATP software simulations using the developed models for evaluation of surges in a typical distribution network subjected to direct lightning strikes at the primary circuit. Furthermore, simulations of internal response of a low-voltage installation with connected equipment and subjected to lightning surges in its entrance is performed using the Pspice software. The work summarizes practical and useful information about the low-voltage surge studies on low-voltage systems.

As linhas de distribuição de energia estão freqüentemente expostas a sobretensões causadas por descargas atmosféricas diretas e indiretas. As formas de onda dessas sobretensões têm uma faixa de variação muito ampla e podem diferir bastante do impulso atmosférico normalizado utilizado em ensaios para verificação da adequação dos projetos das isolações dos equipamentos frente a sobretensões atmosféricas (1,2 / 50 microssegundos). É fato conhecido que a suportabilidade das isolações depende não só da amplitude como da forma de onda das solicitações. Diferentes modelos têm sido propostos para se estimar o desempenho das isolações frente a impulsos não normalizados, sendo o modelo do efeito disruptivo (disruptive effect model) um dos mais utilizados. Existem, contudo, diferentes métodos de aplicação desse modelo, ou seja, diferentes formas de se estimar os parâmetros necessários para a sua aplicação. Este trabalho visa avaliar o comportamento dielétrico de isoladores de média tensão e analisar os principais métodos para estimativa da suportabilidade desses equipamentos frente a sobretensões atmosféricas com formas de onda diferentes da normalizada. Para essa avaliação foram realizados ensaios em um isolador tipo pino, de porcelana, com tensão nominal de 15 kV, nos quais foram utilizadas, além do impulso atmosférico normalizado, outras ondas selecionadas com base em resultados de medição e de cálculo. Modificações realizadas no circuito de um gerador de impulsos de alta tensão convencional permitiram a geração de tensões com formas de onda bastante semelhantes às de sobretensões induzidas por descargas atmosféricas tanto em linhas de tamanho natural como em experimentos realizados com modelo reduzido. São apresentados e discutidos os resultados dos ensaios de tensão disruptiva de impulso atmosférico a 50 % e as curvas tensão-tempo (U x t) obtidas para cada impulso, considerando ambas as polaridades. A avaliação dos métodos de aplicação do modelo do efeito disruptivo foi realizada com base em comparações entre as curvas tensão-tempo obtidas nos ensaios e as curvas previstas por cada modelo, para cada uma das ondas selecionadas. / Overhead distribution lines are often exposed to lightning overvoltages, whose waveshapes vary widely and can differ substantially from the standard impulse voltage waveshape used to test electric equipment insulation against lightning surges (1.2 / 50 microseconds wave). It is well known that the voltage withstand capability of insulation depends not only on the amplitude but also on the voltage waveshape. Different models have been proposed for predicting the strength of insulation subjected to impulses of non-standard waveshapes. One of the most commonly used is the \"disruptive effect model\". There are, however, different methods of applying this model, that is, different ways of estimating the parameters needed for its application. This thesis aims at evaluating the dielectric behavior of medium voltage insulators subjected to impulses of non-standard waveshapes, as well as at evaluating the main methods for predicting their dielectric strength against such impulses. For the analysis, tests were performed on a pin type porcelain insulator with rated voltage of 15 kV, using, besides the standard lightning impulse voltage waveshape, other s waveshapes selected based on the characteristics of measured and calculated lightning overvoltages. Modifications made to the circuit of a conventional impulse voltage generator allowed to obtain voltage waveshapes very similar to those of lightning-induced voltages measured in experiments conducted both in lines of natural size and in reduced model. The test results relative to the critical lightning impulse flashover voltage (U50) and the volt-time characteristics obtained for the positive and negative polarities of each waveshape are presented and discussed. The evaluation of the methods of determining the parameters of the disruptive effect model was based on comparisons between the volt-time curves obtained from the laboratory tests and those predicted by each method, for each of the selected voltage waveshapes.

Este trabalho apresenta uma análise dos surtos em redes aéreas secundárias de distribuição causados por descargas atmosféricas diretas no circuito primário. Alguns trabalhos publicados sobre o fenômeno são comentados, sendo também analisados vários outros estudos relativos à modelagem de componentes. No trabalho, os principais componentes da rede foram modelados e incluídos na representação de uma topologia típica (com as linhas primária e secundária). Assim, foram considerados: transformador de distribuição, isoladores, pára-raios, cargas (consumidores) e resistências de aterramento. Os modelos foram validados, quando possível, através de ensaios em laboratório. Algumas alternativas de proteção da rede secundária foram consideradas. Foi verificada a influência de alguns parâmetros relevantes tais como amplitude e tempo de frente da corrente da descarga, resistências de aterramento, modelos de cargas e posição da descarga. Os resultados foram obtidos por simulações computacionais realizadas através do programa ATP (Alternative Transients Program). São apresentadas formas de onda de sobretensões nos consumidores. Também são apresentados e discutidos valores de corrente e energia nos dispositivos de proteção, fornecendo informações sobre as alternativas de proteção. / This work presents an evaluation of surges in low-voltage overhead distribution lines caused by direct lightning strikes in medium voltage lines. Some publications concerning the phenomenon are commented and several other studies used during the process of modeling of the components are also analysed. The main components of the distribution system were modeled and included. So, a typical distribution network topology (with the primary and secondary lines) was represented including its components: distribution transformer, insulators, surge arresters, loads and ground resistances. The performance of the developed models, whenever possible, was verified by laboratory tests. Some possibilities of the secondary protection were included. Parameters having major effect on the results, such as the lightning current amplitude and front time, the values of grounding resistances, the models of the loads and the lightning strike position were taken into consideration in the study. The results were obtained by simulations performed using the ATP (Alternative Transients Program). Waveforms are presented in order to provide information on the characteristics of the overvoltages in the consumers along the line. Currents, as well as energy absorbed by the low-voltage surge arresters are aldo presented and discussed, providing useful information about the performance of some protection alternatives.