A conexão de geradores distribuídos em sistemas de distribuição deve ser cuidadosamente avaliada para que os mesmos auxiliem efetivamente na melhoria do desempenho das redes elétricas, buscando reduzir ou eliminar eventuais situações que causem a degradação da qualidade da energia elétrica fornecida aos consumidores, entre outros aspectos. Neste contexto, existem vários trabalhos que analisam a influência da conexão de geradores distribuídos no perfil de tensão da rede elétrica, frequência, desequilíbrio de fases e distorção harmônica. No entanto, há poucos trabalhos analisando os efeitos da desconexão de geradores distribuídos na qualidade da energia fornecida aos consumidores. Uma vez operando em paralelo com a rede de distribuição, esses geradores influenciam o perfil de tensão e o comportamento dos dispositivos reguladores de tensão. Como consequência, sua desconexão pode provocar variações de tensão intensas causando danos ou mau funcionamento às cargas. A desconexão pode ser repentina ou devido à atuação da proteção anti-ilhamento, seguida dos procedimentos de religamento automático do alimentador, se houver. Visando estudar este problema, o qual tende a se tornar uma nova preocupação das concessionárias de energia elétrica, e no intuito de minimizar e/ou eliminar os possíveis efeitos negativos dessas variações de tensão, esta pesquisa propõe o desenvolvimento de um método de controle dos taps dos reguladores de tensão. Neste método, o controle dos taps foi modelado como um problema de otimização, minimizando as violações de tensão mencionadas anteriormente e também a quantidade de operações dos reguladores de tensão ao longo de um dia típico. A otimização foi solucionada com um Algoritmo Genético e os resultados obtidos indicaram que é possível minimizar as variações de tensão usando a curva de carga do sistema para planejar a operação dos reguladores de tensão. / The connection of distributed generators in an electric power system should be evaluated carefully to ensure that they effectively assist in improving the performance of electrical networks, reducing or eliminating any situations that cause degradation of the power quality of the consumers, and other issues. In this context, there are several studies that analyze the influence of generators connected to distribution systems and how they affect the frequency, cause variations in voltage magnitude, voltage unbalance and harmonic distortion. However, there are a few studies analyzing the effects that the disconnection of distributed generators induces to the power quality of consumers. Once operating in parallel with the distribution network, these generators have an effect on voltage variations and voltage regulator devices. As a result, disconnection can cause severe voltage variations causing damage or malfunction to the loads. The disconnection may be sudden or due to the action of anti-islanding protection, followed by the procedure to reconnect the substation, if it is possible. In order to study this problem, which tends to become a new power quality concern for electric utilities, and in order to minimize and / or eliminate the possible side effects of the voltage variations, this research proposes the development of a control method of voltage regulators\' taps. In this method, the control of taps was modeled as an optimization problem which aimed to minimize these voltage variations aforementioned and also the amount of voltage regulator operations over a typical day. The optimization was solved by a Genetic Algorithm and the results obtained demonstrate that it is possible to minimize the voltage variation by using the system load curve to plan the operation of voltage regulators.

Submitted by SBI Biblioteca Digital (sbi.bibliotecadigital@puc-campinas.edu.br) on 2017-03-23T14:50:03Z No. of bitstreams: 1 ADOLFO BLENGINI NETO.pdf: 3955942 bytes, checksum: 45ddc01c026b2c6b88359672fba01257 (MD5) / Made available in DSpace on 2017-03-23T14:50:03Z (GMT). No. of bitstreams: 1 ADOLFO BLENGINI NETO.pdf: 3955942 bytes, checksum: 45ddc01c026b2c6b88359672fba01257 (MD5) Previous issue date: 2017-02-16 / Pontif?cia Universidade Cat?lica de Campinas ? PUC Campinas / This study proposes the development of an environment for optimization of the operations of electrical distribution systems. The environment is proposed for the modern electrical distribution networks considering the possibility of inclusion of distributed generation and mesh topology. The environment is divided into three modules. The first module consists of standardizing the input and organization data of the network in memory using techniques of object-oriented software engineering. This approach simplifies the processes of nodal analysis of the circuits, improves the performance of the solution and allows reusing the objects and operations in other implementations. The second module is responsible for analyzing and represents network characteristics: topology, load model and distributed generation points. The third consists of the BFS, FW and OCF methods to perform the current flow calculation and allows the user to choose the desired algorithm, being able to present the currents and voltages in each iteration. The choice of different methods in the optimization environment allows the use of the most adherent method to the different network topologies, the types of load, the flexibility in the use of capacity constraints of the elements of the network and the inclusion of generation limits and voltage limits. In order to verify the adhesion and the efficiency of the environment, simulations were carried out on balanced three-phase circuits of primary distribution of 11, 33 and 400 buses with different load models, radial or mesh topology, with and without distributed generation. / Esta pesquisa prop?e-se ao desenvolvimento de um ambiente para otimiza??o da opera??o de sistemas de distribui??o de energia. O ambiente ? aderente ?s modernas redes de distribui??o de energia por considerar a possibilidade de inclus?o de gera??o distribu?da e topologia em malha. O ambiente est? dividido em tr?s m?dulos. O primeiro m?dulo consiste na padroniza??o dos dados de entrada e organiza??o da rede em mem?ria no formato de grafo utilizando t?cnicas de engenharia de software orientada a objetos. Este enfoque simplifica os processos de an?lises nodais dos circuitos, melhora o desempenho da solu??o e permite reaproveitar os objetos e opera??es em outras implementa??es. O segundo m?dulo ? respons?vel pela an?lise e representa??o das caracter?sticas da rede: topologia, modelo de cargas e pontos de gera??o distribu?da. O terceiro consiste dos m?todos BFS, FW e OCF para a execu??o do c?lculo do fluxo de corrente e d? a op??o ao usu?rio de escolha do enfoque desejado, podendo apresentar as correntes e tens?es em cada itera??o. A op??o de escolha de diferentes m?todos no ambiente de otimiza??o possibilita o uso do m?todo mais aderentes ?s diferentes topologias de rede, aos tipos modelos de carga, a flexibilidade no uso de restri??es de capacidade dos elementos da rede e a inclus?o de limites de gera??o e limites de tens?o. Com a finalidade de comprovar a ader?ncia e efici?ncia do ambiente foram realizadas simula??es em circuitos trif?sicos equilibrados de distribui??o prim?ria com 11, 33 e 400 barras com modelos de carga constante, topologia radial, anel, com e sem gera??o distribu?da.

Made available in DSpace on 2017-07-10T16:41:32Z (GMT). No. of bitstreams: 1 Dissertacao Altamira Queiroz2.pdf: 2299194 bytes, checksum: 07ecb127ebc11ad21a0cb551e23c2f1b (MD5) Previous issue date: 2016-02-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / One of the main problems currently faced by electric utilities is the occurrence of energy losses in the distribution network caused by fraud and electricity theft. Because of the financial losses and risks to public safety, the development of solutions to detect and combat fraud in the distribution networks is of the utmost importance. This work presents an analysis of computational intelligence algorithms to extract knowledge in databases with information from monthly energy consumption to identify consumption patterns with anomalies which could represent fraud. The algorithms Artificial Neural Networks and Support Vector Machines were tested to see which one perform better on the identification consumption patterns with abnormalities. Tests have shown that the algorithms used are able to detect patterns in electricity consumption curves, including special situations of fraud that manual techniques did not detect. / Um dos principais problemas que enfrentam atualmente as empresas concessionárias de energia elétrica é a ocorrência de perdas de energia na rede de distribuição, causadas por fraudes e furtos de energia elétrica. Sendo que tais problemas provocam prejuízos financeiros e também colocam em risco a segurança pública, é de grande interesse das concessionárias encontrar soluções para detectar e combater fraudes nas redes de distribuição de energia elétrica. Neste conceito, o presente trabalho apresenta uma análise dos algoritmos de Inteligência Computacional para extrair conhecimento de bases de dados de informações de consumo mensal de energia elétricas de usuários de uma determinada concessionária, a fim de identificar padrões de consumo com anomalias que representem possíveis fraudes nas redes de distribuição de energia elétrica. Para detectar padrões nas curvas de consumo, foram utilizados algoritmos de Redes Neurais Artificiais e Máquinas de Vetores de Suporte. Após a criação dos modelos, estes foram testados para verificar qual seria o melhor algoritmo para a detecção de padrões de consumo com anomalias, e os resultados obtidos, foram então, comparados com uma base de dados fornecida pela concessionária com a verificação manual dos usuários. Os testes demonstraram que os algoritmos utilizados são capazes de detectar padrões nas curvas de consumo de energia elétrica, inclusive detectando situações especiais de fraudes que técnicas manuais não detectaram.

Abstract not available

Over the last several decades, electricity consumption and generation have continually grown. Investment in the Transmission and Distribution (T&D) infrastructure has been minimal and it has become increasingly difficult and expensive to permit and build new power lines. At the same time, a growing increase in the penetration of renewable energy resources is causing an unprecedented level of dynamics on the grid. Consequently, the power grid is congested and under stress. To compound the situation, the utilities do not possess detailed information on the status and operating margins on their assets in order to use them optimally. The task of monitoring asset status and optimizing asset utilization for the electric power industry seems particularly challenging, given millions of assets and hundreds of thousands of miles of power lines distributed geographically over millions of square miles. The lack of situational awareness compromises system reliability, and raises the possibility of power outages and even cascading blackouts. To address this problem, a conceptual Power Line Sensor Network (PLSN) is proposed in this research. The main objective of this research is to develop a distributed PLSN to provide continuous on-line monitoring of the geographically dispersed power grid by using hundreds of thousands of low-cost, autonomous, smart, and communication-enabled Power Line Sensor (PLS) modules thus to improve the utilization and reliability of the existing power system. The proposed PLSN specifically targets the use of passive sensing techniques, focusing on monitoring the real-time dynamic capacity of a specific span of a power line under present weather conditions by using computational intelligence technologies. An ancillary function is to detect the presence of incipient failures along overhead power lines via monitoring and characterizing the electromagnetic fields around overhead conductors. This research integrates detailed modeling of the power lines and the physical manifestations of the parameters being sensed, with pattern recognition technologies. Key issues of this research also include design of a prototype PLS module with integrated sensing, power and communication functions, and validation of the Wireless Sensor Network (WSN) technology integrated to this proposed PLSN.

La calidad de energía eléctrica incluye la calidad del suministro y la calidad de la atención al cliente. La calidad del suministro a su vez se considera que la conforman dos partes, la forma de onda y la continuidad. En esta tesis se aborda la continuidad del suministro a través de la localización de faltas. Este problema se encuentra relativamente resuelto en los sistemas de transmisión, donde por las características homogéneas de la línea, la medición en ambos terminales y la disponibilidad de diversos equipos, se puede localizar el sitio de falta con una precisión relativamente alta. En sistemas de distribución, sin embargo, la localización de faltas es un problema complejo y aún no resuelto. La complejidad es debida principalmente a la presencia de conductores no homogéneos, cargas intermedias, derivaciones laterales y desbalances en el sistema y la carga. Además, normalmente, en estos sistemas sólo se cuenta con medidas en la subestación, y un modelo simplificado del circuito. Los principales esfuerzos en la localización han estado orientados al desarrollo de métodos que utilicen el fundamental de la tensión y de la corriente en la subestación, para estimar la reactancia hasta la falta. Como la obtención de la reactancia permite cuantificar la distancia al sitio de falta a partir del uso del modelo, el Método se considera Basado en el Modelo (MBM). Sin embargo, algunas de sus desventajas están asociadas a la necesidad de un buen modelo del sistema y a la posibilidad de localizar varios sitios donde puede haber ocurrido la falta, esto es, se puede presentar múltiple estimación del sitio de falta.Como aporte, en esta tesis se presenta un análisis y prueba comparativa entre varios de los MBM frecuentemente referenciados. Adicionalmente se complementa la solución con métodos que utilizan otro tipo de información, como la obtenida de las bases históricas de faltas con registros de tensión y corriente medidos en la subestación (no se limita solamente al fundamental). Como herramienta de extracción de información de estos registros, se utilizan y prueban dos técnicas de clasificación (LAMDA y SVM). Éstas relacionan las características obtenidas de la señal, con la zona bajo falta y se denominan en este documento como Métodos de Clasificación Basados en el Conocimiento (MCBC). La información que usan los MCBC se obtiene de los registros de tensión y de corriente medidos en la subestación de distribución, antes, durante y después de la falta. Los registros se procesan para obtener los siguientes descriptores: a) la magnitud de la variación de tensión ( dV ), b) la variación de la magnitud de corriente ( dI ), c) la variación de la potencia ( dS ), d) la reactancia de falta ( Xf ), e) la frecuencia del transitorio ( f ), y f) el valor propio máximo de la matriz de correlación de corrientes (Sv), cada uno de los cuales ha sido seleccionado por facilitar la localización de la falta. A partir de estos descriptores, se proponen diferentes conjuntos de entrenamiento y validación de los MCBC, y mediante una metodología que muestra la posibilidad de hallar relaciones entre estos conjuntos y las zonas en las cuales se presenta la falta, se seleccionan los de mejor comportamiento.Los resultados de aplicación, demuestran que con la combinación de los MCBC con los MBM, se puede reducir el problema de la múltiple estimación del sitio de falta. El MCBC determina la zona de falta, mientras que el MBM encuentra la distancia desde el punto de medida hasta la falta, la integración en un esquema híbrido toma las mejores características de cada método. En este documento, lo que se conoce como híbrido es la combinación de los MBM y los MCBC, de una forma complementaria. Finalmente y para comprobar los aportes de esta tesis, se propone y prueba un esquema de integración híbrida para localización de faltas en dos sistemas de distribución diferentes. Tanto los métodos que usan los parámetros del sistema y se fundamentan en la estimación de la impedancia (MBM), como aquellos que usan como información los descriptores y se fundamentan en técnicas de clasificación (MCBC), muestran su validez para resolver el problema de localización de faltas. Ambas metodologías propuestas tienen ventajas y desventajas, pero según la teoría de integración de métodos presentada, se alcanza una alta complementariedad, que permite la formulación de híbridos que mejoran los resultados, reduciendo o evitando el problema de la múltiple estimación de la falta. / Power quality includes the supply and customer support quality. The supply quality considers two aspects, the wave shape and continuity. In this thesis the fault location problem, topic related with supply continuity is considered. Fault location is a relatively solved problem in power transmission systems, due to the homogeneous characteristics of the power line, measurements in both terminals and also the availability equipment such as fault locators normally included in distance relays. However, in power distribution systems the fault location is a complex problem which remains unsolved. The complexity is mainly because the presence of laterals, load taps, non homogeneous conductors, unbalances in the system and load. In addition, these power systems only have measurements at the substation and a simplified model of the power network. The main efforts to solve this problem have been oriented to the development of impedance based methods. Because of the reactance estimation makes possible the estimation of the distance to the faulted node by using the circuit model, those methods are considered as Model Based Methods (MBM). However the main drawbacks are related to the requirement of a good system model and to the possibility of multiple estimation of the location of the fault due to the three-shape of such networks. As a result, in this thesis an analysis and a comparative test between several MBM frequently cited is presented. In addition, the solution of the fault location is complemented by using methods which use more than the rms values of current and voltage obtained from fault databases. As tool to relate this information with the fault location, two classification techniques are used and tested (LAMDA and SVM). These relate the voltage and current characteristics to the faulted zone and are denoted in this document as Classification Methods Based on the Knowledge (CMBK).The information used by CMBK is obtained from current and voltage fault registers measured at the distribution substation, before, during and after the fault. These registers are pre-processed to obtain the following characteristics or descriptors: a) The magnitude of the voltage variation between the steady states of fault and pre-fault ( dV ), b) the magnitude of the current variation between the steady states of fault and pre-fault ( dI ), c) the magnitude of the apparent power variation between the steady states of fault and pre-fault ( dS ), d) the magnitude of the reactance as seen from the substation ( Xf ), e) the frequency of the transient caused by the fault ( f ), and f) the maximum eigenvalue of the correlation matrix of the currents ( Sv ). By using these descriptors, several training and validation sets were used with CMBK and by means of a proposed methodology it is shown how to relate these sets with the faulted zone and also to select those which offer the best performances.The application results demonstrate how by combining the MBM with the CMBK it is possible to reduce the multiple estimation of the fault location. The CMBK is used to determine the faulted zone while the MBM finds the distance from the measurement point to the faulted node. Thus the integration in a hybrid approach uses the best characteristics of each method. In this document, the term hybrid is used to describe the complementary combination of MBM and CMBK. Finally and aimed to compare the thesis results, an integration hybrid scheme to fault location is proposed and tested in two different power distribution systems. Both, methods which use the system parameters and are based on the impedance estimation (MBM), and those which use the information represented by the signal descriptors and are based in classification techniques (CMBK) have shown the capability to solve the problem of fault location. The two proposed methodologies have advantages and drawbacks, but according to the integration theory presented, high complementarity has been reached. This makes possible the development of a hybrid approach used to avoid or reduces the multiple estimation of the fault location.

Thèse (D.Eng.)-- Université du Québec à Chicoutimi, 2002. / Document électronique également accessible en format PDF. CaQCU

Thesis (M.S.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (MPhil)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Electrical energy has become an indispensable part of the modern world, supporting industries and economic systems. Any disruption of supply is felt immediately in all spheres of life. The operation of a power system is a complex process involving rotating machines that may fail from time even though they are maintained regularly. The overhead transmission system is likewise prone to faults caused by environmental factors such as pollution and lightning. Power authorities therefore operate their systems in such a way that they have sufficient reserve capacity available to allow for contingencies. In the last decade of the previous century a condition developed, for various reasons, that the reserve margin was too small in the South African electricity supply system. At the end of 2005, a spate of failures occurred at Koeberg power station and later in 2007 serious coal supply problems developed at the large power stations in Mpumalanga, aggravating the situation. This research project focuses on the complexity of the task of the reporter when reporting on occurrences such as these. It is required to convey the factual situation to the readers, avoiding alarmism and sensationalism. At the same time the reporter also has a role to play in educating the readers. It was a difficult task, seeing that the reporters were not necessary versed in the technical field. They therefore had to rely on Eskom’s spokespersons. In this project newspaper clippings of various Western Cape newspapers containing the word Eskom were analysed. The method of analysis was content analysis. Firstly the quantitative content analysis was used to obtain distribution of articles over the period and among newspapers. Thereafter the topics covered and the types of article were obtained for the various newspapers and years. Next articles for 2006 and 2008 were investigated using qualitative content analysis. Certain attributes in the articles were detected manually and a profile was obtained for each newspaper for each year period. Questionnaires were sent to reporters responsible for some of the articles and to a technical expert who was consulted regularly by the news reporters. It was found that the number of articles and style of presentation vary among the newspapers. There is evidence of framing of Eskom as incompetent. / AFRIKAANSE OPSOMMING: Elektriese energie het ¢n onontbeerlike deel van die moderne wêreld geword wat nywerhede en ekonomiese stelsels ondersteun. Enige onderbreking van toevoer word onmiddellik in alle lewensfere gevoel. Die werking van kragstelsel is komplekse proses met roterende masjiene en ander toerusting wat onderworpe aan faling is, selfs al word dit in stand gehou. Die oorhoofse transmissiestelsel is ook onderworpe aan foute wat deur omgewingsfaktore soos besoedeling en weerlig veroorsaak word. Kragvoorsieners bedryf daarom hul stelsels so dat hulle voldoende reserwekapasiteit het om toe te laat vir gebeurlikhede. In die laaste dekade van die vorige eeu het die toestand, om verskeie redes, ontwikkel dat die reserwemarge in die Suid-Afrikaanse stelsel te klein geword het. Teen die einde van 2005 het reeks falings by Koeberg kragstasie plaasgevind en later in 2007 het ernstige steenkoolvoorsieningsprobleme by die groot kragstasies in Mpumalanga ontstaan en dus die situasie vererger. Hierdie navorsingsprojek fokus op die kompleksiteit van die taak van die verslaggewer as oor sulke gebeure verslag gedoen word. Dit word vereis om die feitelike situasie oor te dra sonder alarmisme en sensasie. Terselfdertyd moet die verslaggewer ook rol speel om die lesers op te voed. Dit is moeilike taak daar die verslaggewers nie noodwendig belese in die tegniese vakgebied is nie. Hulle moes dus staatmaak op Eskom se spreekbuise. In hierdie projek is koerantuitknipsels van verskeie Wes-Kaapse koerante wat die woord Eskom bevat, ontleed. Die metode wat gebruik is, is inhoudsanalise. Eerstens is kwantitatiewe inhoudsanalise gebruik om die verspreiding van artikels oor die tydperk en tussen die koerante te verkry. Daarna is die onderwerpe wat gedek is verkry vir die onderskeie koerante en jare. Vervolgens is artikels van 2006 en 2008 ondersoek deur kwalitatiewe inhoudsanalise te doen. Sekere kenmerke is in die artikels opgespoor en profiel is verkry vir elke koerant en elke jaarperiode. Vraelyste is aan verslaggewers wat sommige artikels geskryf het en ook aan tegniese deskundige wat gereeld deur verslaggewers genader is, gestuur. Dit is bevind dat die getal artikels en die styl van aanbieding wissel tussen die koerante Daar is ook tekens van raming van Eskom as onbekwaam.

Este trabalho estuda as potenciais melhorias na eficiência energética e vazão do método híbrido de requisição automática de retransmissão (Hybrid Automatic Retransmission Request, HARQ). A análise inclui as camadas física (PHY) e de acesso ao meio (MAC). É investigada a relação de compromisso gerada pelo HARQ, o qual demanda uma menor potência de transmissão para uma certa probabilidade de falha alvo ao custo de mais acessos ao canal. Uma vez que a competição para acesso ao canal na camada MAC é bastante custosa em termos de energia e atraso, os resultados mostram que a utilização do HARQ leva a uma grande melhoria de performance devido ao menor número de nós competidores – uma consequência da redução na potência de transmissão necessária. Contra-intuitivamente, esta análise leva à conclusão que retransmissões podem diminuir o atraso, melhorando a performance do sistema. Finalmente, são também investigados valores ótimos para o número de retransmissões permitidas, visando maximizar vazão ou/e eficiência energética. / This work studies the potential improvements in terms of energy efficiency and throughput of a hybrid automatic retransmission request (HARQ) mechanism. The analysis includes both the physical (PHY) and medium access (MAC) layers. We investigate the trade-off provided by HARQ, which demands reduced transmit power for a given target outage probability at the cost of more accesses to the channel. Since the competition for channel access at the MAC layer is very expensive in terms of energy and delay, our results show that HARQ leads to great performance improvements due to the decrease in the number of contending nodes – a consequence of the reduced required transmit power. Counter-intuitively, our analysis leads to the conclusion that retransmissions may decrease the delay, improving the system performance. Finally, we investigate the optimum values for the number of allowed retransmissions in order to maximize either the throughput or the energy efficiency.