The electric power distribution system usually operates a radial configuration, with tie switches between circuits to provide alternate feeds. The losses would be minimized if all switches were closed, but this is not done because it complicates the system's protection against overcurrents. Whenever a component fails, some of the switches must be operated to restore power to as many customers as possible. As loads vary with time, switch operations may reduce losses in the system. Both of these are applications for reconfiguration. The problem is combinatorial, which precludes algorithms that guarantee a global optimum. Most existing reconfiguration algorithms fall into two categories. In the first, branch exchange, the system operates in a feasible radial configuration and the algorithm opens and closes candidate switches in pairs. In the second, loop cutting, the system is completely meshed and the algorithm opens candidate switches to reach a feasible radial configuration. Reconfiguration algorithms based on linearized transshipment, neural networks, heuristics, genetic algorithms, and simulated annealing have also been reported, but not widely used. These existing reconfiguration algorithms work with a simplified model of the power system, and they handle voltage and current constraints approximately, if at all. The algorithm described here is a constructive method, using a full nonlinear power system model that accurately handles constraints. The system starts with all switches open and all failed components isolated. An optional network power flow provides a lower bound on the losses. Then the algorithm closes one switch at a time to minimize the increase in a merit figure, which is the real loss divided by the apparent load served. The merit figure increases with each switch closing. This principle, called discrete ascent optimal programming (DAOP), has been applied to other power system problems, including economic dispatch and phase balancing. For reconfiguration, the DAOP method's greedy nature is mitigated with a backtracking algorithm. Approximate screening formulas have also been developed for efficient use with partial load flow solutions. This method's main advantage is the accurate treatment of voltage and current constraints, including the effect of control action. One example taken from the literature shows how the DAOP-based algorithm can reach an optimal solution, while adjusting line voltage regulators to satisfy the voltage constraints. / Ph. D.

No description available.

El presente trabajo surge debido a que la empresa en estudio de producción de calzados, desea cubrir la demanda insatisfecha que ha venido presentando, la cual se ha visto altamente beneficiada por el aumento de pedidos en los últimos años. Debido a ello, la presente investigación propone la implementación de una alternativa de distribución de planta en la empresa aplicando la metodología de la Planificación Sistemática de la Distribución (SLP) con lo que se logra la reducción de las distancias recorridas para incrementar la capacidad productiva y disminuir los tiempos de traslados entre estaciones, además de proponer el uso la herramienta 5’S, la cual permite crear una cultura de orden y limpieza en la organización obteniendo la reducción de tiempos muertos por la saturación de espacios debido a desórdenes y búsqueda de materiales. La propuesta mencionada en el presente trabajo empieza explicando los conceptos y metodologías que son necesarias para realizar el análisis, luego describe la situación actual de la empresa a nivel de sus procesos, productos y principales causas que originan la entrega tardía de pedidos. Posteriormente, se realizará el análisis y evaluación de las alternativas para la selección de la mejor propuesta de distribución de planta para la empresa evaluando términos cualitativos y cuantitativos. A sí mismo, se implementan un manual para la aplicación de los principios 5S en las áreas más críticas. Luego, se realizará la evaluación económica de la alternativa escogida y el plan de implementación. Finalmente, se validará la información para obtener los beneficios. / The manufacturing specifications used by small leather and footwear businesses are neither up to date nor based on innovative production and new technologies. Consequently, their production times are higher, rendering them unable to sufficiently compete against other developed countries. Thus, this study seeks an innovative way to reduce times that do not add value to the product, such as reducing travel distances between stations, and proposes improving procedures for a better monitoring of the resources required. As a whole, this proposal focuses on designing a model to minimize the displacement of different processes. This practice is currently being implemented in the manufacturing sector, but not in the footwear sector. The proposal provides broad results, saving around 33% in transfer times and 85% in distance traveled in footwear production. / Trabajo de Suficiencia Profesional

Prior to the year 2007, Eskom Distribution followed a method of load forecasting (now referred to as legacy method in this report) that was based on collecting customer applications, historical load trending, and relied on the planner’s knowledge of the area to a large extent. It was based in a conventional Microsoft Excel spreadsheet. On seeking to improve its load forecasting approach, the utility adopted a technique that was based on spatial forecasting. This new technique was called a geographical based load forecasting (GLF) technique which was performed by using a custom based tool, called PowerGLF. The aim of this research was to assess any improvements (or lack thereof) that were brought about by adopting the GLF method as compared to the legacy method that was used previously. The hypothesis to be tested was declared as: “The use of the GLF method that was introduced to Eskom Distribution Planning brings about the improvement on the planning process of infrastructure that is adequate, reliable and economic, when compared to the legacy method that was used before it.” To carry out this assessment, a case study method was followed. Real network studies that were compiled in 2006 and 2007 were used. These network studies were based on GLF method and the legacy method. The load forecasts from the case studies were evaluated on forecast accuracy, how they influenced the planning of adequate, reliable and economic (ARE) network infrastructure and their impact on the procurement and construction of the network infrastructure (which represent the actual utility expenditure on infrastructure). The statistical comparative analysis was done. The research results revealed that the legacy method was more accurate than the GLF method in both the case studies that were evaluated. However, regarding the ability of a load forecast method to support the planning process, the GLF method showed to be supporting the planning of adequate, reliable and economic infrastructure better than the legacy method. It was found that the forecast error for the GLF and legacy method do not affect the utility infrastructure procurement and construction. Based on the test results, the study reached a conclusion that the use of the GLF method that was introduced to Eskom Distribution Planning brings about the improvement in the planning process of infrastructure that is adequate, economic and reliable when compared to the legacy method that was used before it. The author wishes to express that the results of this study must not be taken as a generic conclusive finding regarding the evaluated load forecasting methods; they are applicable to the tested case studies. To get to a general conclusive result, more case studies would need to be carried out where clear and consistent evidence on performance of these load forecasting methods will be seen. The findings of this study can be used as part of a larger sample if such a larger population of case studies was to be evaluated. The methodology followed in this research can be repeated and followed when similar assessments are done in future.

No description available.

Neste trabalho, apresenta-se um método para o Planejamento de Redes de Distribuição Secundária. O modelo básico desenvolvido baseia-se em técnica de programação dinâmica a fim de selecionar a política de evolução de trocas de transformadores de distribuição e rede secundária, com mínimo custo operacional dentro de limites de qualidade de serviço, para o atendimento de carga crescente no tempo em uma área de estudo restrita. Inicialmente, apresenta-se a filosofia básica do método, incluindo-se os dados necessários, critérios de planejamento e metodologia para o cálculo elétrico de redes secundárias. Em sequência, são apresentados três modelos para a solução do problema; tais modelos são diferenciados pela eliminação progressiva de hipóteses simplificativas. Nos dois primeiros modelos, a carga e seu crescimento são supostos uniformemente distribuídos ao longo dos trechos da rede secundária. No terceiro modelo, a distribuição da carga dos pontos presentes na rede secundária, durante o período de estudo, é estabelecida por procedimento randômico, com o único vínculo de serem mantidos os mercados globais de demanda e número de consumidores na área em estudo. Posteriormente, estabelece-se um exemplo de aplicação que permite proceder à comparação entre os três modelos desenvolvidos. Finalizando o trabalho, são estabelecidas as conclusões, possibilidades de aplicação do método em diversos estudos do sistema de Distribuição Secundária e são tecidos comentários sobre tópicos para ulterior desenvolvimento. / This work focuses on a method for the Planning of Secondary Distribution Systems. The basic model deals with dynamic programming in order to get an optimized design - Distribution Transformer and Secondaries - which presents the lowest operation cost within service quality limits in order to supply growing load on a restricted area. Initially the basic concepts of the method are presented, including the establishment of the data base, planning criteria and methodology in order to get operating conditions at secondary networks. Concerning this method, three computational models were established. These models differ form each other as far as some of the simplified hypothesis are eliminated. The first two models consider a uniform distribution of loads along the secondary system. The third model establishes a randomic distribution of loads on the restricted studying area. Following an application example, comparison is proceeded among the developed models. Eventually the conclusions, some possible applications of the method on Distribution system studies and research topics for further developments are settled.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 5 uppsatser.

Neste trabalho, apresenta-se um método para o Planejamento de Redes de Distribuição Secundária. O modelo básico desenvolvido baseia-se em técnica de programação dinâmica a fim de selecionar a política de evolução de trocas de transformadores de distribuição e rede secundária, com mínimo custo operacional dentro de limites de qualidade de serviço, para o atendimento de carga crescente no tempo em uma área de estudo restrita. Inicialmente, apresenta-se a filosofia básica do método, incluindo-se os dados necessários, critérios de planejamento e metodologia para o cálculo elétrico de redes secundárias. Em sequência, são apresentados três modelos para a solução do problema; tais modelos são diferenciados pela eliminação progressiva de hipóteses simplificativas. Nos dois primeiros modelos, a carga e seu crescimento são supostos uniformemente distribuídos ao longo dos trechos da rede secundária. No terceiro modelo, a distribuição da carga dos pontos presentes na rede secundária, durante o período de estudo, é estabelecida por procedimento randômico, com o único vínculo de serem mantidos os mercados globais de demanda e número de consumidores na área em estudo. Posteriormente, estabelece-se um exemplo de aplicação que permite proceder à comparação entre os três modelos desenvolvidos. Finalizando o trabalho, são estabelecidas as conclusões, possibilidades de aplicação do método em diversos estudos do sistema de Distribuição Secundária e são tecidos comentários sobre tópicos para ulterior desenvolvimento. / This work focuses on a method for the Planning of Secondary Distribution Systems. The basic model deals with dynamic programming in order to get an optimized design - Distribution Transformer and Secondaries - which presents the lowest operation cost within service quality limits in order to supply growing load on a restricted area. Initially the basic concepts of the method are presented, including the establishment of the data base, planning criteria and methodology in order to get operating conditions at secondary networks. Concerning this method, three computational models were established. These models differ form each other as far as some of the simplified hypothesis are eliminated. The first two models consider a uniform distribution of loads along the secondary system. The third model establishes a randomic distribution of loads on the restricted studying area. Following an application example, comparison is proceeded among the developed models. Eventually the conclusions, some possible applications of the method on Distribution system studies and research topics for further developments are settled.

The high cost of grid extension to rural areas, often characterized by scattered communities with low load densities, requires the use of low cost electrification technologies to ensure economic viability. In Single Wire Earth Return (SWER) power distribution networks, the earth itself forms the current return path of the single phase system leading to significant cost savings on conductors, poles and poletop hardware compared to conventional systems. However, challenges exist in SWER with regard to earthing and safety as well as the dependence on earth conductivity to supply consumer loads. This work presents models for the optimal planning of SWER distribution networks. The earth return path is modeled as a conductor based on the Carson line model taking into consideration specific ground properties of the considered location. A load flow algorithm for radial SWER networks is subsequently formulated whereby both overhead line and ground voltages and currents are determined. First, heuristic planning models are developed based on the SWER load flow model. The objective of the heuristic models is to determine the optimum feeder configuration and overhead conductor subject to SWER load flow constraints and load growth over several time periods. Whereas the resulting solutions are good, they may not necessarily be globally optimum. Optimization models are then developed using mixed integer non-linear programming (MINLP) with the aim of obtaining global solutions to the SWER network planning problem. Since the MINLP formulations are limited to the accurate analysis of limited size networks, considerations and approximations for the analysis of larger networks are presented. The developed models are applied to a case study in Uganda to test their practical application. In addition, comparative studies are done to determine how the proposed optimization models compare with previous distribution planning models. The numerical analysis includes the impact of deterministic distributed generation on the SWER planning problem. Results showed consistent performance of the proposed heuristic and optimization models, which also compared well with conventional models. The optimization models gave more cost-effective solutions to the SWER planning problem than the heuristic models. However, the former models had higher computational cost than the latter. The inclusion of distributed generation allowed for cheaper network solutions to be obtained. The models are applicable to the planning of Single Wire Earth Return networks for isolated mini-grids, grid-extension to previously un-electrified rural areas as well as the upgrade of SWER feeders in existing installations. / <p>QC 20121207</p> / Sustainable Technological Development in the Lake Victoria Region

Resumo: Neste trabalho apresentam-se dois métodos para serem aplicados na previsão espacial de demanda elétrica, os quais simulam as influências de cargas especiais nas vizinhanças e utilizam os sistemas multiagentes para caracterizar a área de serviço, mostrando assim, a dinâmica dos grupos sociais em uma cidade à procura dos recursos necessários para suas atividades. O primeiro sistema multiagente foi desenvolvido para obter a previsão espacial de demanda elétrica de toda área de serviço e o segundo sistema multiagente modela a influência de cargas especiais nas vizinhanças. Estes sistemas apresentam um caráter estocástico, para simular a estocasticidade dos usuários nos sistemas de distribuição. Os métodos apresentados consideram a disponibilidade atual de dados nas empresas do setor, usando só o banco de dados comercial da empresa de serviço elétrico e o conjunto de dados georreferenciados dos elementos da rede. Uma das contribuições deste trabalho é de utilizar um número real para representar a demanda elétrica esperada de cada subárea fornecendo, deste modo, um melhor dado de entrada para realizar o planejamento de expansão da rede elétrica. A metodologia proposta foi testada em um sistema real de uma cidade de médio porte. Como resultados são gerados mapas de cenários futuros de previsão espacial de demanda para a área de estudo, que mostram a localização espaço-temporal das novas cargas. Cada mapa mostra as subáreas onde a nova demanda é esperada, com um número real para o valor da quantidade desta demanda. Os resultados obtidos variam entre 5 a 10 % em diferentes simulações, quando comparadas com as fornecidas pelo departamento de planejamento da empresa elétrica que aplica uma metodologia manual, que utiliza o conhecimento e as decisões do planejador para determinar o crescimento da demanda. / Abstract: This paper presents two methods to be applied in the spatial electric load forecasting, which simulate the influences of special loads in the vicinity and use the multi-agent systems to characterize the service area, thus showing the dynamics of social groups in a city seeking the necessary resources for their activities. The first multi-agent system was developed for the spatial electric load forecasting of the entire service area and the second multi-agent system models the influence of special load in the vicinity. These systems have a stochastic character, to simulate the stochasticity of users in distribution systems. The method presented in this work considers that the utilities have access only to basic information, using only the commercial consumer database and georeferenced data set of the network elements. One of the contributions of this work is to use a real number to represent the expected demand in each subarea providing thus a better input data to perform the expansion planning of the distribution systems grid. The proposed methodology was tested in a real system of a midsize city. As results are generated maps of forecast future scenarios of spatial demand for the study area, showing the location of the new space-time loads. Each map shows the subareas where the new demand is expected, with a real number to the value of the quantity of demand. The results vary between 5 to 10% in different simulations, when compared with those provided by the planning department electrical distribution utility that applies an electric manual, which uses the knowledge and decisions of the planner to determine the growth of demand. / Orientador: Antonio Padilha Feltrin / Coorientador: Edgar Manuel Carreño Franco / Banca: Carlos Roberto Minussi / Banca: Sérgio Luís Haffner / Mestre