This thesis is the product of an effort to develop a CubeSat Conceptual Design Tool for the California Polytechnic State University CubeSat Laboratory. Such a tool is necessary due to inefficiencies with the current conceptual design process. It is being developed to increase accessibility, reduce design time, and promote good systems engineering within CubeSat development. The development of the architecture of a conceptual design tool, the core user-interface element, and the completion of a module for the electrical power subsystem is the focus of this thesis. The architecture is built around different modules to design different subsystems that work in conjunction. The module in the tool was developed to allow a user to size an electrical power subsystem, and that is the basis for future subsystem development. Model-based Systems Engineering was also utilized as an endpoint for the tool’s outputs, and a CubeSat Model has been built for this effort. Validation has been successful on the Conceptual Design Tool as implemented at this time, so the tool it is ready to design CubeSat electrical power subsystems and be expanded upon by other tool developers.

No description available.

Transformers are the most expensive and critical asset in any electrical power network. Their failure results in long interruption of power supply with consequent loss of reliability and revenue. Understanding and detection of the failure mechanism helps in avoiding catastrophic failures, unplanned outages and improving the power system reliability. Oil impregnated paper (OIP) and pressboards form the main soild insulation in a transformer. Life of the transformer is governed mostly by the life of OIP insulation. Until recently, it was thought that ageing of the OIP insulation in power transformer and its eventual failure, is mainly a function of temperature and electrical stresses. However, it has now been realized that the moisture causes rapid degradation of OIP and needs a special attention. Considering its practical relevance, this research program was formulated with goals: (i) to study the ageing of OIP insulation under temperature and moisture stresses, (ii) to seek correlation between diagnostic ageing indices and end-of-life (EOL) and (iii) to develop a life model for OIP considering moisture along with the thermal stress. Observing that working with actual transformers or even the prototypes are rather inordinately expensive, experiments were conducted with paper strips immersed in oil in test tubes with paper to oil ratio kept same as that in power transformers. In order to cater for the statistical nature of the phenomena, adequate numbers of test specimens were employed (25 numbers for each experiment). Experiments were conducted for two years at temperatures 90°C, 110°C & 120°C and moisture 1%, 2% & 3%. Following the literature, the degree of polymerization (DP) was chosen as the primary index for ageing. As measurement of DP is not only destructive, but also impractical on most of the working transformers, with an aim to develop suitable diagnostic indices for ageing, 2-furfural (2-FAL) and oxides of carbon (CO and CO2) were also measured. Empirical relation between ageing and amount of stresses and time have been deduced for the relevant range. Limiting value of these indices to prescribe the end-of-life, as well as, their correlation with DP have been worked out and reported. In order to bring the role of moisture explicitly, based on earlier work on multi-stress ageing, a multiplicative power law supplementing the Arrhenius factor is envisaged. Accordingly, a phenomenological combined stress model involving the time to failure, temperature, and moisture content is deduced. Based on the experimental results, this model is statistically validated and the values of parameters appearing in the model is obtained. Thus the combined stress model enables one to estimate the life of OIP insulation at any temperature and moisture under synergy. In summary, this work through experimental and analytical approach has contributed to the evaluation of the aging of OIP insulation used in power transformers under the combined action of moisture and temperature.

Electrical energy supply in South Africa, provided by ESKOM, has become more expensive with regular price increases in the past seven years. Increases on an annual basis have seen the Mega flex tariffs quadruple in the years from 2007 to 2014. ESKOM is the sole supplier of electricity to Safripol, a polymer producer of which the manufacturing facility is located in Sasolburg, South Africa. This study will provide contextual information on what impact the escalation in cost of this utility has on the financial returns of the business. Independent power generation within the boundaries of the manufacturing site has become essential in order to alleviate the impact of inflated electricity costs, by at least 10% of the current total demand from ESKOM. Primary research includes different types of alternative electricity generation techniques that will be able to deliver a practical solution to the business. The means of operation, required resources and cost to produce are set out to provide input into concrete models that are scaled to the potentials applicable to the production facility. Total alternative electricity generation added up to almost half of the current total site electricity demand from ESKOM. This finding was truly beyond the expectations of the case study and clearly set out how understated the potential to generate electricity is within the industrial sector. / MIng (Development and Management Engineering), North-West University, Potchefstroom Campus, 2015

Electrical energy supply in South Africa, provided by ESKOM, has become more expensive with regular price increases in the past seven years. Increases on an annual basis have seen the Mega flex tariffs quadruple in the years from 2007 to 2014. ESKOM is the sole supplier of electricity to Safripol, a polymer producer of which the manufacturing facility is located in Sasolburg, South Africa. This study will provide contextual information on what impact the escalation in cost of this utility has on the financial returns of the business. Independent power generation within the boundaries of the manufacturing site has become essential in order to alleviate the impact of inflated electricity costs, by at least 10% of the current total demand from ESKOM. Primary research includes different types of alternative electricity generation techniques that will be able to deliver a practical solution to the business. The means of operation, required resources and cost to produce are set out to provide input into concrete models that are scaled to the potentials applicable to the production facility. Total alternative electricity generation added up to almost half of the current total site electricity demand from ESKOM. This finding was truly beyond the expectations of the case study and clearly set out how understated the potential to generate electricity is within the industrial sector. / MIng (Development and Management Engineering), North-West University, Potchefstroom Campus, 2015

This research proposes, implements and analyses a novel framework for multiobjective optimisation through evolutionary computing aimed at, but not restricted to, real-world problems in the engineering design domain. Evolutionary algorithms have been used to tackle a variety of non-linear multiobjective optimisation problems successfully, but their success is governed by key parameters which have been shown to be sensitive to the nature of the particular problem, incorporating concerns such as the number of objectives and variables, and the size and topology of the search space, making it hard to determine the best settings in advance. This work describes a real-encoded multi-objective optimising evolutionary algorithm framework, incorporating a genetic algorithm, that uses self-adaptive mutation and crossover in an attempt to avoid such problems, and which has been benchmarked against both standard optimisation test problems in the literature and a real-world airfoil optimisation case. For this last case, the minimisation of drag and maximisation of lift coefficients of a well documented standard airfoil, the framework is integrated with a freeform deformation tool to manage the changes to the section geometry, and XFoil, a tool which evaluates the airfoil in terms of its aerodynamic efficiency. The performance of the framework on this problem is compared with those of two other heuristic MOO algorithms known to perform well, the Multi-Objective Tabu Search (MOTS) and NSGA-II, showing that this framework achieves better or at least no worse convergence. The framework of this research is then considered as a candidate for smart (electricity) grid optimisation. Power networks can be improved in both technical and economical terms by the inclusion of distributed generation which may include renewable energy sources. The essential problem in national power networks is that of power flow and in particular, optimal power flow calculations of alternating (or possibly, direct) current. The aims of this work are to propose and investigate a method to assist in the determination of the composition of optimal or high-performing power networks in terms of the type, number and location of the distributed generators, and to analyse the multi-dimensional results of the evolutionary computation component in order to reveal relationships between the network design vector elements and to identify possible further methods of improving models in future work. The results indicate that the method used is a feasible one for the achievement of these goals, and also for determining optimal flow capacities of transmission lines connecting the bus bars in the network.

[pt] O controle das tensões dos diversos barramentos de um sistema elétrico de potência tem como objetivo garantir a qualidade da energia fornecida aos consumidores. As tensões devem respeitar níveis regulamentados pelo governo. Atualmente, no Sistema Elétrico de Potência (SEP) brasileiro, a tarefa do controle de tensão, realizada pelos operadores de tempo real, se baseia nos valores e tendências de diversas variáveis (tensões, potências reativas e ativas, sensibilidade dos equipamentos, dentre outras). Para a formação de um operador nessa tarefa são necessários de um a dois anos, tempo que poderia ser reduzido caso um sistema de apoio à decisão dedicado ao problema de controle de tensão estivesse à disposição durante o treinamento. Entretanto, em virtude do grande número de grandezas a serem analisadas e de suas não linearidades, é necessário uma ferramenta automática de apoio à decisão que seja capaz de tratar intrinsecamente relações não lineares. Deste modo, neste trabalho optou-se por desenvolver um sistema baseado em Redes Neurais Artificiais (RNA) para a confecção do sistema sugerido, com o objetivo de indicar a necessidade de realizar ações de controle de tensão utilizando-se dos recursos ou equipamentos disponíveis. O sistema desenvolvido é composto de três módulos: Pré-processamento; Análise e Classificação do evento; e Pós-processamento. Tal sistema serve para sugerir a manobra de equipamentos mais adequada para o controle de tensão. No estudo de caso, o sistema proposto foi avaliado nos equipamentos de controle de tensão (reatores, capacitores e tapes) constantes no Sistema de Transmissão em 765 kV, responsável pela interligação dos sistemas Sul e Sudeste do Brasil. Utilizando dados obtidos do sistema de aquisição em tempo real, diferentes configurações de RNAs foram testadas. Os melhores resultados foram obtidos com uma estrutura de duas redes neurais por equipamento a ser controlado, apresentando, em média, 80% de acerto em relação às manobras realizadas em tempo real. Em virtude da complexidade do problema, os resultados foram considerados mais do que satisfatórios, indicando a aplicabilidade desta técnica para a realização do sistema desejado. / [en] The main objective of the voltage control in Electrical Power System (EPS) is to guarantee the quality of the energy supplied to consumers. The voltage must respect government regulated levels. Currently, on the Brazilian EPS, the voltage control task is carried out by system operators based on diverse information, such as current values, and trends of electric variables (voltages, reactive and active powers, their sensitivities in the control devices performance, amongst others). To fully train a operator in this task it is necessary one or two years, period that could be greatly reduced if a decision support system was available during the operator`s training. However, due to the great number of variables that must be analyzed and their nonlinearity, an automatic decision support tool, capable to treat nonlinear relations, is necessary. Therefore, this work proposes a system based on Artificial Neural Networks (ANN), with the objective to identify the necessity or not to use the voltage control resources in the EPS. The developed system is composed of three modules: Pre-processing; Event Analysis and Classification; and Post-processing. Such decision support system suggests the most adequate equipment maneuver in the voltage control task. In the case study, the proposed system was evaluated using the available voltage control equipments (reactors, capacitors and transformer taps) in the 765 kV Transmission System, main responsible trunk for the interconnection of South and Southeastern Brazilian systems. Using real time data, different ANN configurations have been tested. The best results were obtained with a structure composed of two neural networks, for each controlled equipment, presenting, in average, 80% accuracy in relation to maneuvers occurred in real time. Due to the problem complexity, the results were considered more than satisfactory, indicating the applicability of this technique for the development of the desired system.

Atualmente, a intensidade de campo elétrico, campo magnético e campo eletromagnético é um fator determinante não só para a implantação de novas instalações, mas também, para as instalações existentes no sistema elétrico. Apesar de não existir nenhum estudo conclusivo que comprove a evidência direta entre a exposição a estes campos e os efeitos nocivos na saúde das pessoas, muitos países, inclusive o Brasil, definiram em suas legislações limites básicos à exposição de campos elétrico e magnético provenientes dos sistemas elétricos. Este trabalho tem como objetivo contribuir para análise de campo magnético de linhas subterrâneas de alta tensão existentes ou linhas em fase inicial de projeto, visando atender os limites de exposição vigentes na legislação local. Nele é apresentada a metodologia de cálculo de campo magnético baseada na Lei de Biot-Savart e no princípio da superposição. Estudos analíticos para verificação da influência dos parâmetros de instalação e elétricos de linhas sobre o campo magnético são apresentados para linhas subterrâneas de alta tensão compostas por um e dois circuitos com diferentes tipos de instalação e aterramentos. Comparações entre valores analíticos e valores de medições de campo magnético de linhas subterrâneas de alta tensão existentes em operação também são abordadas neste trabalho. As principais técnicas de mitigação de campo magnético utilizadas em linhas subterrâneas de alta tensão, tais como técnicas de compensação envolvendo laços de cabos e técnicas de blindagens com materiais metálicos externos aos cabos, também são apresentadas. Devido ao campo elétrico externo ao cabo isolado ser praticamente zero, assuntos referentes a este campo não são abordados neste trabalho. Por simplicidade, campo magnético refere-se à densidade de fluxo magnético neste documento. / Nowadays, the intensity of electric field, magnetic field and electromagnetic field is a determining factor, not only for implantation of new installations, but also for existing installations in the power system. Although no exist conclusive study that proves the direct evidence between exposure to these fields and adverse effects on human health, many countries, including Brazil, have defined in their laws basic limits for exposure to electric and magnetic fields produced by the electric system. This work aims to contribute to analysis of magnetic field for both existing high voltage underground lines and lines in initial stage of project, aiming the actual exposure limits of the local legislation. In it, is shown the magnetic field calculation methodology based on the Biot-Savart\'s law and the superposition principle. Analytical studies to verify the influence of installation and electrical parameters of lines on the magnetic field are presented for high voltage underground lines consist of one and two circuits with different types of installation and earthing. Comparisons between analytical and measurement values of magnetic field of existing high voltage underground lines in operation are also addressed in this work. The main mitigation techniques of magnetic field used in high voltage underground lines, such as compensation techniques by loop of cables and shielding by metallic materials, are also presented. Due the electric field outside the insulated cable be practically zero, issues related to the electric field are not addressed in this work. For simplicity, the magnetic field refers to the magnetic flux density in this document.

O processo de estimação de estado em sistemas elétricos de potência está sujeito a três tipos de erros: erros nas medidas analógicas (erros grosseiros); erros devido a informações erradas quanto aos estados de chaves e/ou disjuntores (erros topológicos) e erros causados por informações erradas de algum parâmetro do sistema (erros de parâmetros). É drástico o efeito de erros de parâmetros, para o processo de estimação de estado, normalmente intolerável, sendo, entretanto, menos evidente que os erros grosseiros e topológicos. Aproveitando o fato de que certas medidas não sofrem mudanças significativas de valor, durante um determinado intervalo de tempo, propõe-se uma metodologia para estimação de estado e parâmetros de linhas de transmissão. Na metodologia proposta, que se baseia nas equações normais, o vetor de estado convencional é aumentado para a inclusão dos parâmetros a serem estimados. Este vetor de estado aumentado é então estimado através de uma grande quantidade de medidas, obtidas em diversas amostras, durante um intervalo de tempo em que as variáveis de estado do sistema não tenham sofrido alterações significativas de valor. Esta situação ocorre tipicamente à noite, fora dos horários de pico. Propõe-se também uma metodologia para análise de observabilidade para o estimador proposto. Para comprovar a eficiência das metodologias propostas, vários testes foram realizados, utilizando os sistemas de 6, 14 e 30 barras do IEEE. / The process of power system state estimation is subjected to three types of errors: errors in analogical measurements (gross errors), incorrect information about the status of switching devices (topology errors) and incorrect information about the model of the systems equipment (parameter errors). The effects of parameter errors on the process of power system state estimation are drastic and less evident to detect than gross and topology errors. Taking advantage of the fact that a certain fraction of the measurements varies over a small range in a certain period of time, a methodology to estimative transmission line parameters and state based on normal equations has been proposed. In such methodology, which is based on normal equations, the traditional state vector is expanded to include the parameters to be estimated. This augmented state vector is estimated through a large collection of measurements, recorded within several snapshots of the power system, during which the actual system state varies over a small range. This situation typically occurs during the night off-peak periods. An observability analysis methodology is also proposed for the presented estimator. To prove the efficiency of the methodologies, several tests were made using the systems of 6, 14 and 30 buses from IEEE.

O objetivo do desenvolvimento deste trabalho é tecer uma análise da viabilidade técnica - econômica da modernização do sistema de Proteção da Distribuição, comparando a utilização dos relés digitais aos quais foram incorporadas novas funções, em relação aos relés eletromecânicos e estáticos. As informações apresentadas nesse trabalho mostram que os relés digitais oferecem uma significante economia quanto ao custo de aquisição e implantação, no desenvolvimento dos projetos de aplicação e na manutenção destes equipamentos após instalados em campo. Os relés eletromecânicos tem sido largamente utilizados nos esquemas de proteção de consumidores industriais e residencias de grande porte e nos sistemas de proteção das companhias de eletricidade. Devido a quantidade de peças móveis e freqüentes re-ajustes que estes tipos de equipamentos necessitam, os mesmos demandam muitas horas dispendidas pelo pessoal de calibração e manutenção das empresas de eletricidade. A realização de Estudos de Proteção, com a parametrização destes relés muitas vezes torna-se inviável, sob o ponto de vista de sensibilidade e da coordenação das proteções, devido ao fato de que estes equipamentos possuem ajustes limitados tanto de valores de corrente de partida como na seleção de curvas tempo x corrente utilizadas para temporização das proteções, no caso de relés eletromecânicos de sobrecorrente. Durante os últimos anos, com o advento da evolução da indústria, da micro eletrônica e do desenvolvimento de softwares, os relés digitais veêm substituíndo os relés eletromecânicos e estáticos, tanto em instalações novas como também nas remodelações das instalações mais antigas, nos sistemas elétricos de proteção industrial e de empresas de eletricidade. Realizou-se uma análise quanto ao histórico dos relés de proteção, mostrando o seu desenvolvimento desde os relés mais antigos, tipos eletromecânicos, após os relés estáticos, que foram a evolução dos anteriores e finalmente estudando os relés digitais. Os relés digitais oferecem muitas vantagens se comparados com os relés eletromecânicos e estáticos, as quais serão abordandos em items específicos da revisão de literatura neste trabalho. O trabalho é finalizado com uma análise de casos, onde foram computados e analisados casos, como índices de fornecimento, custos de instalação de relés digitais em substituição à relés e sistemas eletromecânicos e estáticos, utilizados convencionalmente para a proteção em alimentadores de Subestações da Copel - Companhia Paranaense de Energia, com o objetivo de coletar-se e analisar-se, ao longo de 12 meses as reais vantagens e desvantagens da utilização destes equipamentos nos sistemas elétricos de proteção dos circuitos de distribuição de energia. / The purpose of this study is to carry out a technical and economic feasibility assessment of the updating of the Distribution Protection system, comparing the use of digital relays, to which new functions have been integrated, with electromechanical and static relays. Information hereby presented shows that digital relays are significantly cost-effective in terms of acquisition and implementation for developing application projects and in maintaining that equipment after it has been set up in the field. Electromechanical relays have been largely used in protection schemes for large-scale industrial and residential consumers, as well as in security schemes for power plant companies. Because of the large number of moving parts and frequent readjustments required by that type of equipment, many manhours must be put in by calibration and maintenance staff employed by power plant companies. Carrying out a Protection Study that establishes parameters for those relays is often unfeasible given the sensitivity and coordination of the protections, in that the equipment in question has limited adjustments, both in terms of pick-up currents values and of the selection of time curve vs. current used in the protection timer, in the case of overcurrent electromechanical relays. During the last years, with the rise of industrial evolution, microelectronics and software development, digital relays are replacing electromechanical and static relays in electrical security systems used by industrial and power plant company protection, both in new facilities and in refurbished facilities. A study was carried out on the history of protection relays showing how they developed from the older, electromechanical type after the static relays, which evolved form the former, and was concluded with the study of digital relay models. Digital relays provide significant advantages compared to electromechanical and static relays, which will be covered under specific revision items of the references provided herein. The study is concluded by assessing case studies that were accounted for and assessed, such as supply rates, installation costs of digital relays to replace electromechanical and static systems used traditionally to provide protection for COPEL´s (Power Company of the State of Paraná) Substations. The purpose was to collect and analyze, over a 12-month period, the actual advantages and disadvantages of using that type of equipment in electrical systems that provide circuit protection for power distribution.