Desenvolvimento de um sistema de proteção e metodologia para localização de faltas em sistemas de distribuição

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Optimización multiobjetivo inteligente del dimensionamiento energético en sistemas ferroviarios señalizados y en plataformas software de tiempo real

La capacidad de transporte es uno de los baremos fundamentales para evaluar la progresión que puede llegar a tener un área económica y social. Es un sector de elevada importancia para la sociedad actual. Englobado en los distintos tipos de transporte, uno de los medios de transporte que se encuentra más en alza en la actualidad, es el ferroviario. Tanto para movilidad de pasajeros como para mercancías, el tren se ha convertido en un medio de transporte muy útil. Se encuentra dentro de las ciudades, entre ciudades con un radio pequeño entre ellas e incluso cada vez más, gracias a la alta velocidad, entre ciudades con gran distancia entre ellas. Esta Tesis pretende ayudar en el diseño de una de las etapas más importantes de los Proyectos de instalación de un sistema ferroviario: el sistema eléctrico de tracción. La fase de diseño de un sistema eléctrico de tracción ferroviaria se enfrenta a muchas dudas que deben ser resueltas con precisión. Del éxito de esta fase dependerá la capacidad de afrontar las demandas de energía de la explotación ferroviaria. También se debe atender a los costes de instalación y de operación, tanto costes directos como indirectos. Con la Metodología que se presenta en esta Tesis se ofrecerá al diseñador la opción de manejar un sistema experto que como soluciones le plantee un conjunto de escenarios de sistemas eléctricos correctos, comprobados por resolución de modelos de ecuaciones. Correctos desde el punto de vista de validez de distintos parámetros eléctrico, como de costes presupuestarios e impacto de costes indirectos. Por tanto, el diseñador al haber hecho uso de esta Metodología, tendría en un espacio de tiempo relativamente corto, un conjunto de soluciones factibles con las que poder elegir cuál convendría más según sus intereses finales. Esta Tesis se ha desarrollado en una vía de investigación integrada dentro del Centro de Investigaciones Ferroviarias CITEF-UPM. Entre otros proyectos y vías de investigación, en CITEF se ha venido trabajando en estudios de validación y dimensionamiento de sistemas eléctricos ferroviarios con diversos y variados clientes y sistemas ferroviarios. A lo largo de los proyectos realizados, el interés siempre ha girado mayoritariamente sobre los siguientes parámetros del sistema eléctrico: - Calcular número y posición de subestaciones de tracción. Potencia de cada subestación. - Tipo de catenaria a lo largo del recorrido. Conductores que componen la catenaria. Características. - Calcular número y posición de autotransformadores para sistemas funcionando en alterna bitensión o 2x25kV. - Posición Zonas Neutras. - Validación según normativa de: o Caídas de tensión en la línea o Tensiones máximas en el retorno de la línea o Sobrecalentamiento de conductores o Sobrecalentamiento de los transformadores de las subestaciones de tracción La idea es que las soluciones aportadas por la Metodología sugieran escenarios donde de estos parámetros estén dentro de los límites que marca la normativa. Tener la posibilidad de tener un repositorio de posibles escenarios donde los parámetros y elementos eléctricos estén calculados como correctos, aporta un avance en tiempos y en pruebas, que mejoraría ostensiblemente el proceso habitual de diseño para los sistemas eléctricos ferroviarios. Los costes directos referidos a elementos como subestaciones de tracción, autotransformadores, zonas neutras, ocupan un gran volumen dentro del presupuesto de un sistema ferroviario. En esta Tesis se ha querido profundizar también en el efecto de los costes indirectos provocados en la instalación y operación de sistemas eléctricos. Aquellos derivados del impacto medioambiental, los costes que se generan al mantener los equipos eléctricos y la instalación de la catenaria, los costes que implican la conexión entre las subestaciones de tracción con la red general o de distribución y por último, los costes de instalación propios de cada elemento compondrían los costes indirectos que, según experiencia, se han pensado relevantes para ejercer un cierto control sobre ellos. La Metodología cubrirá la posibilidad de que los diseños eléctricos propuestos tengan en cuenta variaciones de coste inasumibles o directamente, proponer en igualdad de condiciones de parámetros eléctricos, los más baratos en función de los costes comentados. Analizando los costes directos e indirectos, se ha pensado dividir su impacto entre los que se computan en la instalación y los que suceden posteriormente, durante la operación de la línea ferroviaria. Estos costes normalmente suelen ser contrapuestos, cuánto mejor es uno peor suele ser el otro y viceversa, por lo que hace falta un sistema que trate ambos objetivos por separado. Para conseguir los objetivos comentados, se ha construido la Metodología sobre tres pilares básicos: - Simulador ferroviario Hamlet: Este simulador integra módulos para construir esquemas de vías ferroviarios completos; módulo de simulación mecánica y de la tracción de material rodante; módulo de señalización ferroviaria; módulo de sistema eléctrico. Software realizado en C++ y Matlab. - Análisis y estudio de cómo focalizar los distintos posibles escenarios eléctricos, para que puedan ser examinados rápidamente. Pico de demanda máxima de potencia por el tráfico ferroviario. - Algoritmos de optimización: A partir de un estudio de los posibles algoritmos adaptables a un sistema tan complejo como el que se plantea, se decidió que los algoritmos genéticos serían los elegidos. Se han escogido 3 algoritmos genéticos, permitiendo recabar información acerca del comportamiento y resultados de cada uno de ellos. Los elegidos por motivos de tiempos de respuesta, multiobjetividad, facilidad de adaptación y buena y amplia aplicación en proyectos de ingeniería fueron: NSGA-II, AMGA-II y ɛ-MOEA. - Diseño de funciones y modelo preparado para trabajar con los costes directos e indirectos y las restricciones básicas que los escenarios eléctricos no deberían violar. Estas restricciones vigilan el comportamiento eléctrico y la estabilidad presupuestaria. Las pruebas realizadas utilizando el sistema han tratado o bien de copiar situaciones que se puedan dar en la realidad o directamente sistemas y problemas reales. Esto ha proporcionado además de la posibilidad de validar la Metodología, también se ha posibilitado la comparación entre los algoritmos genéticos, comparar sistemas eléctricos escogidos con los reales y llegar a conclusiones muy satisfactorias. La Metodología sugiere una vía de trabajo muy interesante, tanto por los resultados ya obtenidos como por las oportunidades que puede llegar a crear con la evolución de la misma. Esta Tesis se ha desarrollado con esta idea, por lo que se espera pueda servir como otro factor para trabajar con la validación y diseño de sistemas eléctricos ferroviarios. ABSTRACT Transport capacity is one of the critical points to evaluate the progress than a specific social and economical area is able to reach. This is a sector of high significance for the actual society. Included inside the most common types of transport, one of the means of transport which is elevating its use nowadays is the railway. Such as for passenger transport of weight movements, the train is being consolidated like a very useful mean of transport. Railways are installed in many geography areas. Everyone know train in cities, or connecting cities inside a surrounding area or even more often, taking into account the high-speed, there are railways infrastructure between cities separated with a long distance. This Ph.D work aims to help in the process to design one of the most essential steps in Installation Projects belonging to a railway system: Power Supply System. Design step of the railway power supply, usually confronts to several doubts and uncertainties, which must be solved with high accuracy. Capacity to supply power to the railway traffic depends on the success of this step. On the other hand is very important to manage the direct and indirect costs derived from Installation and Operation. With the Methodology is presented in this Thesis, it will be offered to the designer the possibility to handle an expert system that finally will fill a set of possible solutions. These solutions must be ready to work properly in the railway system, and they were tested using complex equation models. This Thesis has been developed through a research way, integrated inside Citef (Railway Research Centre of Technical University of Madrid). Among other projects and research ways, in Citef has been working in several validation studies and dimensioning of railway power supplies. It is been working by a large range of clients and railways systems. Along the accomplished Projects, the main goal has been rounded mostly about the next list of parameters of the electrical system: - Calculating number and location of traction substations. Power of each substation. - Type of Overhead contact line or catenary through the railway line. The wires which set up the catenary. Main Characteristics. - Calculating number and position of autotransformers for systems working in alternating current bi-voltage of called 2x25 kV. - Location of Neutral Zones. - Validating upon regulation of: o Drop voltages along the line o Maximum return voltages in the line o Overheating/overcurrent of the wires of the catenary o Avoiding overheating in the transformers of the traction substations. Main objective is that the solutions given by the Methodology, could be suggest scenarios where all of these parameters from above, would be between the limits established in the regulation. Having the choice to achieve a repository of possible good scenarios, where the parameters and electrical elements will be assigned like ready to work, that gives a great advance in terms of times and avoiding several tests. All of this would improve evidently the regular railway electrical systems process design. Direct costs referred to elements like traction substations, autotransformers, neutral zones, usually take up a great volume inside the general budget in railway systems. In this Thesis has been thought to bear in mind another kind of costs related to railway systems, also called indirect costs. These could be enveloped by those enmarked during installation and operation of electrical systems. Those derived from environmental impact; costs generated during the maintenance of the electrical elements and catenary; costs involved in the connection between traction substations and general electric grid; finally costs linked with the own installation of the whole electrical elements needed for the correct performance of the railway system. These are integrated inside the set has been collected taking into account own experience and research works. They are relevant to be controlled for our Methodology, just in case for the designers of this type of systems. The Methodology will cover the possibility that the final proposed power supply systems will be hold non-acceptable variations of costs, comparing with initial expected budgets, or directly assuming a threshold of budget for electrical elements in actual scenario, and achieving the cheapest in terms of commented costs from above. Analyzing direct and indirect costs, has been thought to divide their impact between two main categories. First one will be inside the Installation and the other category will comply with the costs often happens during Railway Operation time. These costs normally are opposed, that means when one is better the other turn into worse, in costs meaning. For this reason is necessary treating both objectives separately, in order to evaluate correctly the impact of each one into the final system. The objectives detailed before build the Methodology under three basic pillars: - Railway simulator Hamlet: This software has modules to configure many railway type of lines; mechanical and traction module to simulate the movement of rolling stock; signaling module; power supply module. This software has been developed using C++ and Matlab R13a - Previously has been mandatory to study how would be possible to work properly with a great number of feasible electrical systems. The target comprised the quick examination of these set of scenarios in terms of time. This point is talking about Maximum power demand peaks by railway operation plans. - Optimization algorithms. A railway infrastructure is a very complex system. At the beginning it was necessary to search about techniques and optimization algorithms, which could be adaptable to this complex system. Finally three genetic multiobjective algorithms were the chosen. Final decision was taken attending to reasons such as time complexity, able to multiobjective, easy to integrate in our problem and with a large application in engineering tasks. They are: NSGA-II, AMGA-II and ɛ-MOEA. - Designing objectives functions and equation model ready to work with the direct and indirect costs. The basic restrictions are not able to avoid, like budgetary or electrical, connected hardly with the recommended performance of elements, catenary and safety in a electrical railway systems. The battery of tests launched to the Methodology has been designed to be as real as possible. In fact, due to our work in Citef and with real Projects, has been integrated and configured three real railway lines, in order to evaluate correctly the final results collected by the Methodology. Another topic of our tests has been the comparison between the performances of the three algorithms chosen. Final step has been the comparison again with different possible good solutions, it means power supply system designs, provided by the Methodology, testing the validity of them. Once this work has been finished, the conclusions have been very satisfactory. Therefore this Thesis suggest a very interesting way of research and work, in terms of the results obtained and for the future opportunities can be created with the evolution of this. This Thesis has been developed with this idea in mind, so is expected this work could adhere another factor to work in the difficult task of validation and design of railway power supply systems.

Proteção de linhas de transmissão de sistemas VSC-HVDC utilizando limitadores de corrente de falta

Tecnologias HVDC que utilizam conversores do tipo fonte de tensão, o VSC-HVDC, ainda não são completamente difundidas e aplicadas no Brasil, em contraste com outros países que começaram a estudar e empregar este tipo de transmissão. Comparado com o HVDC tradicional, o VSC-HVDC é uma tecnologia de transmissão mais eficiente e pode superar deficiências encontradas na transmissão em corrente contínua convencional. O VSC-HVDC pode ser utilizado de maneira mais eficiente nas novas redes de energia, para alimentar ilhas, integração de geração eólica, renovação das linhas em centros urbanos, aplicações multiterminais e conexão com sistemas fracos. Por se tratar de uma tecnologia recente, o VSC-HVDC ainda não é amplamente adotado e uma das principais limitações da utilização destes sistemas é a sua fragilidade diante faltas na linha de corrente contínua. Neste contexto, limitadores de corrente de falta (LCF) podem ser utilizados para minimizar o impacto das faltas. A ação dos limitadores é benéfica ao sistema durante condições de falta, contudo, ainda assim é necessária a atuação do sistema de proteção para extinguir a condição faltosa. Portanto, este trabalho visa propor e avaliar um novo esquema de proteção que opere de maneira seletiva e confiável para sistemas VSC-HVDC na presença de LCF baseados em materiais supercondutores ou LCF indutivos. Para tanto, foram implementadas quatro funções de proteção tradicionais das linhas em CC, a saber: direcional de corrente, diferencial, sobrecorrente com restrição de tensão e ondas viajantes, e ainda, foi proposta uma nova função de proteção, a de condutância, a qual apresentou o menor tempo de identificação de falta, considerando as faltas mais severas. Adicionalmente, foi avaliado o comportamento destas funções quando o sistema apresenta os LCF em série com a linha. Foi demonstrado que é possível extrair os benefícios dos LCF sem deteriorar a qualidade dos resultados das funções de proteção, o que aumenta a segurança e confiabilidade dos sistemas VSC-HVDC, uma vez que os impactos das faltas são minimizados e as mesmas são identificadas em um curto intervalo de tempo.

Simulation of power station protection equipment

Computer programs have been developed to enable the coordination of fuses and overcurrent relays for radial power systems under estimated fault current conditions. The grading curves for these protection devices can be produced on a graphics terminal and a hard copy can be obtained. Additional programs have also been developed which could be used to assess the validity of relay settings (obtained under the above conditions) when the transient effect is included. Modelling of a current transformer is included because transformer saturation may occur if the fault current is high, and hence the secondary current is distorted. Experiments were carried out to confirm that distorted currents will affect the relay operating time, and it is shown that if the relay current contains only a small percentage of harmonic distortion, the relay operating time is increased. System equations were arranged to enable the model to predict fault currents with a generator transformer incorporated in the system, and also to include the effect of circuit breaker opening, arcing resistance, and earthing resistance. A fictitious field winding was included to enable more accurate prediction of fault currents when the system is operating at both lagging and leading power factors prior to the occurrence of the fault.

A series-dynamic-resistor-based converter protection scheme for doubly-fed induction generator during various fault conditions

This paper proposes a new converter protection method, primarily based on a series dynamic resistor (SDR) that avoids the doubly-fed induction generator (DFIG) control being disabled by crowbar protection during fault conditions. A combined converter protection scheme based on the proposed SDR and conventional crowbar is analyzed and discussed. The main protection advantages are due to the series topology when compared with crowbar and dc-chopper protection. Various fault overcurrent conditions (both symmetrical and asymmetrical) are analyzed and used to design the protection in detail, including the switching strategy and coordination with crowbar, and resistance value calculations. PSCAD/EMTDC simulation results show that the proposed method is advantageous for fault overcurrent protection, especially for asymmetrical faults, in which the traditional crowbar protection may malfunction.

Multiterminal DC wind farm collection grid internal fault analysis and protection design

The multiterminal dc wind farm is a promising topology with a voltage-source inverter (VSI) connection at the onshore grid. Voltage-source converters (VSCs) are robust to ac-side fault conditions. However, they are vulnerable to dc faults on the dc side of the converter. This paper analyzes dc faults, their transients, and the resulting protection issues. Overcurrent faults are analyzed in detail and provide an insight into protection system design. The radial wind farm topology with star or string connection is considered. The outcomes may be applicable for VSCs in the multi-VSC dc wind farm collection grid and VSC-based high-voltage direct current (HVDC) offshore transmission systems.

Protection issue discussion of DC network development:circuit breaker or fault-tolerant converter

This paper provides a discussion on future direct current (DC) network development in terms of system protection under DC-side fault scenarios. The argument between appropriate DC circuit breaker and new DC fault-tolerant converters is discussed after a review on DC technology development and bottleneck issues that require proper solutions. The overcurrent/cost curve of power-electronic DC circuit breakers (CB) superimposed to voltage-source converter (VSC) systems is derived and compared with other possible fault-tolerant power conversion options. This in-advance planning of protection capability is essential for the future development of DC networks.

Permanent magnet synchronous generator based wind power generation system fault protection schemes

The PMSG-based wind power generation system protection is presented in this paper. For large-scale systems, a voltagesource converter rectifier is included. Protection circuits for this topology are studied with simulation results for cable permanent fault conditions. These electrical protection methods are all in terms of dumping redundant energy resulting from disrupted path of power delivery. Pitch control of large-scale wind turbines are considered for effectively reducing rotor shaft overspeed. Detailed analysis and calculation of damping power and resistances are presented. Simulation results including fault overcurrent, DC-link overvoltage and wind turbine overspeed are shown to illustrate the system responses under different protection schemes to compare their application and effectiveness.

Proteção em sistemas elétricos com geração distribuída utilizando a transformada wavelet

A typical electrical power system is characterized by centr alization of power gene- ration. However, with the restructuring of the electric sys tem, this topology is changing with the insertion of generators in parallel with the distri bution system (distributed gene- ration) that provides several benefits to be located near to e nergy consumers. Therefore, the integration of distributed generators, especially fro m renewable sources in the Brazi- lian system has been common every year. However, this new sys tem topology may result in new challenges in the field of the power system control, ope ration, and protection. One of the main problems related to the distributed generati on is the islanding formation, witch can result in safety risk to the people and to the power g rid. Among the several islanding protection techniques, passive techniques have low implementation cost and simplicity, requiring only voltage and current measuremen ts to detect system problems. This paper proposes a protection system based on the wavelet transform with overcur- rent and under/overvoltage functions as well as infomation of fault-induced transients in order to provide a fast detection and identification of fault s in the system. The propo- sed protection scheme was evaluated through simulation and experimental studies, with performance similar to the overcurrent and under/overvolt age conventional methods, but with the additional detection of the exact moment of the fault.