Nesta pesquisa, apresentam-se os principais eventos relacionados com a proteção de transformadores e sua correlação com os distúrbios de qualidade da energia elétrica (QEE). Neste sentido, foi desenvolvido um algoritmo que utiliza a transformada Wavelet (TW) e a lógica Fuzzy (LF) para classificar os eventos transitórios associados à proteção de transformadores. Estes eventos foram observados em um sistema elétrico de potência (SEP) simulado com a utilização do software Alternative Transients Program (ATP). Importa ressaltar que o sistema modelado apresenta transformadores ligados em paralelo, possibilitando o estudo de eventos decorrentes desta situação, como a energização solidária (Sympathetic Inrush). Por este SEP, modelado sobre parâmetros reais, foram simuladas várias situações transitórias, que provocam o aparecimento de correntes diferenciais, sendo estas direcionadas para análise do algoritmo desenvolvido. Afirma-se que, nos testes realizados, o algoritmo proposto apresentou um desempenho satisfatório perante as mais variadas situações a que foi submetido, identificando as causas das correntes diferenciais, sejam proporcionadas por defeitos ou por outras condições de operação aplicadas. / In this research, the main events related to the transformer protection and its correlation with the power quality disturbances (PQ) are presented. In this context, an algorithm based on Wavelet transform (WT) and Fuzzy logic (FL) was developed to classify the transient events associated with the transformer protection. These events were observed in an electrical power system (EPS) simulated using the Alternative Transients Program (ATP) software. It should be emphasized that the modeled system presents transformers connected in parallel, allowing the study of events of this situation, such as sympathetic inrush. For the simulated EPS, modeled based on real parameters, various transients situationswere simulated, causing the appearance of differentials currents which were directed to the analysis. The proposed algorithm showed a satisfactory performance tomany situations, identifying the causes of the differentials currents, either provided by faults or other operation conditions.

Le transformateur de puissance est un équipement essentiel d’un réseau électrique et le plus coûteux dans les postes. Pour augmenter son degré de disponibilité et de fiabilité, il est nécessaire d’appliquer la manœuvre contrôlée afin de diminuer la saturation du noyau lors de l’enclenchement, et donc limiter les courants d’appel. Ces derniers sont asymétriques, d’amplitude élevée, et riches en harmoniques. Ils peuvent causer des effets indésirables comme le disfonctionnement des dispositifs de protections, l’endommagement mécanique des enroulements du transformateur et réduire en général la durée de vie et la qualité des systèmes. Une technique efficace pour réduire ces courants d’appel est de mettre sous tension le transformateur quand le flux dynamique généré par la source est égal à son flux rémanent. Un modèle simplifié du transformateur de puissance est adopté pour l’analyse des phénomènes physiques liés à l’application des manœuvres. Pour évaluer le degré de faisabilité de cette technique, des simulations sont effectuées en utilisant le simulateur de réseau EMTP. Les contraintes requises pour chacun des composants du système de manœuvre contrôlée comme les segments de ligne, les disjoncteurs sont étudiées en détail pour déterminer l’algorithme de calcul de l’instant optimal de manœuvres. Ensuite des tests de validation statistiques sont effectués afin d’évaluer les performances des différentes approches employées. Enfin une étude consacrée à la reconstitution du flux rémanent via un transformateur capacitif de tension (TCT) est menée pour appliquer l’algorithme de manœuvre contrôlée dans les postes en utilisant les équipements de mesure déjà existants. / Power transformers are vital equipment in electrical networks and are the most expensive ones in substations. In order to increase their availability and reliability, controlled switching must be applied for reducing cores saturation during its energization, called “inrush currents”. These inrush currents are asymmetrical, high-magnitude, harmonic-rich, and may cause many undesirable effects such as maloperation of protective relays and fuse, mechanical damage to the transformer winding and generally reduce the lifetime and quality of power systems. An efficient technique to reduce these inrush currents is to energize the transformer when the dynamic flux generated by the source is equal to its residual flux. A simplified model is adopted to analyze the physical phenomena related to the switching applications. In order to assess the feasibility of this technique, numerous simulations have been performed using EMTP simulator. The critical requirements for each component of the controlled switching system such as pieces of line, circuit breakers have been studied in detail in order to determine the best switching instant calculation algorithm. Then statistical validation tests have been conducted to evaluate the performances of its different approaches. Finally a study dedicated to the reconstitution of residual flux using a capacitive voltage transformer (CVT) has been carried on in order to apply the controlled switching algorithm in substations using their existing measurement equipments.

Nesta pesquisa, apresentam-se os principais eventos relacionados com a proteção de transformadores e sua correlação com os distúrbios de qualidade da energia elétrica (QEE). Neste sentido, foi desenvolvido um algoritmo que utiliza a transformada Wavelet (TW) e a lógica Fuzzy (LF) para classificar os eventos transitórios associados à proteção de transformadores. Estes eventos foram observados em um sistema elétrico de potência (SEP) simulado com a utilização do software Alternative Transients Program (ATP). Importa ressaltar que o sistema modelado apresenta transformadores ligados em paralelo, possibilitando o estudo de eventos decorrentes desta situação, como a energização solidária (Sympathetic Inrush). Por este SEP, modelado sobre parâmetros reais, foram simuladas várias situações transitórias, que provocam o aparecimento de correntes diferenciais, sendo estas direcionadas para análise do algoritmo desenvolvido. Afirma-se que, nos testes realizados, o algoritmo proposto apresentou um desempenho satisfatório perante as mais variadas situações a que foi submetido, identificando as causas das correntes diferenciais, sejam proporcionadas por defeitos ou por outras condições de operação aplicadas. / In this research, the main events related to the transformer protection and its correlation with the power quality disturbances (PQ) are presented. In this context, an algorithm based on Wavelet transform (WT) and Fuzzy logic (FL) was developed to classify the transient events associated with the transformer protection. These events were observed in an electrical power system (EPS) simulated using the Alternative Transients Program (ATP) software. It should be emphasized that the modeled system presents transformers connected in parallel, allowing the study of events of this situation, such as sympathetic inrush. For the simulated EPS, modeled based on real parameters, various transients situationswere simulated, causing the appearance of differentials currents which were directed to the analysis. The proposed algorithm showed a satisfactory performance tomany situations, identifying the causes of the differentials currents, either provided by faults or other operation conditions.

Este trabalho apresenta um conjunto de métodos para a proteção e o monitoramento de transformadores de potência baseado em sistemas inteligentes e na aplicação das transformadas de Clarke e Wavelet. A abordagem inteligente utilizada permite analisar a condição operativa dos transformadores de potência e detectar a ocorrência de defeito interno, distinguindo-a de outras situações de operação, como, a energização, a energização solidária, a saturação dos transformadores de corrente e a sobreexcitação. As tomadas de decisão das técnicas desenvolvidas são realizadas pela lógica fuzzy após o pré-processamento dos sinais de entrada por meio de diversos métodos, os quais variam de acordo com o algoritmo que esta sendo executado. Os algoritmos propostos foram testados por meio de simulações realizadas através do software Alternative Transients Program (ATP). É importante salientar que nas simulações do ATP foram modelados diversos equipamentos que constituem o sistema elétrico de potência, incluindo um gerador síncrono com regulação de velocidade, linhas de transmissão com variação em frequência, transformadores de potência com suas respectivas curvas de saturação, transformadores de potencial e de corrente. Estas modelagens tiveram por objetivo gerar dados das distintas situações de operação para a verificação e análise da metodologia proposta. Os resultados da pesquisa mostram a aplicabilidade dos algoritmos propostos na proteção e no monitoramento dos transformadores de potência, mesmo nas condições mais adversas, como na ocorrência da saturação dos transformadores de corrente, uma vez que os sinais de entrada distorcidos pela saturação são corrigidos por uma rede neural artificial. Os resultados apresentados comparam as respostas obtidas pelas técnicas propostas em relação às saídas de um relé comercial, habilitado à proteção diferencial percentual. / This work presents a set of methods for protecting and monitoring power transformers based on intelligent systems and the application of Clarke and Wavelet transforms. The intelligent approach allowed us to analyze the operating condition of power transformers and it discriminates between an internal fault and different operating conditions, as energization, sympathetic inrush, saturation of current transformers and overexcitation. Decision making is performed by fuzzy logic after the preprocessing of the input signals through various methods, varying according to which algorithm is running. It is important to point out that in the simulations using ATP many different power system equipment had been modeled, including a synchronous generator with speed regulation, transmission lines with variation in frequency, power transformers with their saturation curves, potential transformers and current transformers. The objective of these tests was to generate data for distinct situations for the verification and the analysis of the proposed methodologies. The results of the research show the applicability of the algorithms considered in protection and monitoring of power transformers, even in adverse conditions, such as saturation of current transformers, since the input signals are distorted by CT saturation corrected by artificial neural network. The results are compared to the ones presented by a commercial percentage differential relay.

Power and Generator Transformers are important and expensive elements of a power system. Inadvertent failure of Power Transformers would cause long interruption in power supply with consequent loss of reliability and revenue to the supply utilities. The mineral oil impregnated paper, OIP, is an insulation of choice in large power transformers in view of its excellent dielectric and other properties, besides being relatively inexpensive. During the normal working regime of the transformer, the insulation thereof is subjected to various stresses, the more important among them are, electrical, thermal, mechanical and chemical. Each of these stresses, appearing singly, or in combination, would lead to a time variant deterioration in the properties of insulation, called Ageing. This normal and inevitable process of degradation in the several essential properties of the insulation is irreversible, is a non-Markov physico-chemical reaction kinetic process. The speed or the rapidity of insulation deterioration is a very strong function of the magnitude of the stresses and the duration over which they acted. This is further compounded, if the stresses are in synergy. During the processes of ageing, some, or all the vital properties undergo subtle changes, more often, not in step with the duration of time over which the damage has been accumulated. Often, these changes are non monotonic, thus presenting a random or a chaotic picture and understanding the processes leading to eventual failure becomes difficult. But, there is some order in this chaos, in that, the time average of the changes over short intervals of time, seems to indicate some degree of predictability. The status of insulation at any given point in time is assessed by measuring such of those properties as are sensitive to the amount of ageing and comparing it with earlier measurements. This procedure, called the Diagnostic or nondestructive Testing, has been in vogue for some time now. Of the many parameters used as sensitive indices of the dynamics of insulation degradation, temporal changes in temperatures at different locations in the body of the transformer, more precisely, the winding hot spots (HST) and top oil temperature (TOT) are believed to give a fairly accurate indication of the rate of degradation. Further, an accurate estimation of the temperatures would enable to determine the loading limit (loadability) of power transformer. To estimate the temperature rise reasonably accurately, one has to resort to classical mathematical techniques involving formulation and solution of boundary value problem of heat conduction under carefully prescribed boundary conditions. Several complications are encountered in the development of the governing equations for the emergent heat transfer problems. The more important among them are, the inhomogeneous composition of the insulation structure and of the conductor, divergent flow patterns of the oil phase and inordinately varying thermal properties of conductor and insulation. Validation and reconfirmation of the findings of the thermal models can be made using state of the art methods, such as, Artificial Intelligence (AI) techniques, Artificial Neural Network (ANN) and Genetic Algorithm (GA). Over the years, different criteria have been prescribed for the prediction of terminal or end of life (EOL) of equipment from the standpoint of its insulation. But, thus far, no straightforward and unequivocal criterion is forth coming. Calculation of elapsed life in line with the existing methodology, given by IEEE, IEC, introduces unacceptable degrees of uncertainty. It is needless to say that, any conformal procedure proposed in the accurate prediction of EOL, has to be based on a technically feasible and economically viable consideration. A systematic study for understanding the dynamical nature of ageing in transformers in actual service is precluded for reasons very well known. Laboratory experiments on prototypes or pro-rated units fabricated based on similarity studies, are performed under controlled conditions and at accelerated stress levels to reduce experimental time. The results thereof can then be judiciously extrapolated to normal operating conditions and for full size equipment. The terms of reference of the present work are as follows; 1. Computation of TOT and HST Theoretical model based on Boundary Value Problem of Heat Conduction Application of AI Techniques 2. Experimental Investigation for estimating the Elapsed Life of transformers Based on the experimental investigation a semi-empirical expression has been developed to estimate the loss of life of power and station transformer by analyzing gas content and furfural dissolved in oil without performing off-line and destructive tests.

Desde seu lançamento, em 2002, a Norma IEC 61850 vem evoluindo para se tornar o padrão adotado nos Sistemas de Automação de Subestações. Dentre seus vários aspectos, destacam- se os serviços de tempo real, que permitem a implementação de funções de automação e de proteção dentro da subestação através da troca de mensagens específicas entre Dispositivos Eletrônicos Inteligentes através de um barramento digital de rede de dados. O objetivo central deste trabalho é explorar algumas das questões que envolvem a implementação de uma classe de serviços de tempo real: a transmissão de valores amostrados através de Serviços SMV, definidos pela Norma IEC 61850-9. Primeiramente, apresenta-se um breve resumo das principais características da Norma IEC 61850 que possibilitam o atendimento dos três requisitos por ela estabelecidos como base: a interoperabilidade entre dispositivos de diferentes fabricantes, a versatilidade na configuração e reconfiguração do Sistema de Automação da Subestação, e a possibilidade de implementação de novas tecnologias. Em seguida, explora-se com maior profundidade todos os aspectos relevantes à implementação dos Serviços SMV. Devido à complexidade deste assunto, o autor propõe abordá-lo sob a ótica de cinco tópicos interdependentes: variações da Norma IEC 61850-9, confiabilidade do barramento de processo, sincronismo de tempo, análise da qualidade da medição e segurança cibernética. Com base nos resultados apresentados neste estudo, propõem-se duas plataformas, um protótipo de Transformador de Potencial Óptico e um protótipo de Relé de Proteção Diferencial para transformadores de potência, com o objetivo de explorar alguns dos aspectos pertinentes à implementação de um barramento de processo de acordo com a Norma IEC 61850-9. Também foram realizados testes de geração e transmissão de mensagens contendo valores de amostras de tensão/corrente do sistema elétrico (denominadas de SV Messages) com a finalidade de implementá-las de fato e avaliar as ferramentas de mercado disponíveis. Por fim foi proposto um modelo para a simulação do sistema de potência em conjunto com a rede de comunicação utilizando o programa Matlab/Simulink. O autor espera que este trabalho contribua para esclarecer os vários conceitos envolvidos na implementação do barramento de processo definido pela Norma IEC 61850-9, auxiliando na pesquisa e no desenvolvimento de novas ferramentas e dispositivos, e no aprimoramento da Norma IEC 61850. / Since its introduction, in 2002, the IEC 61850 Standard has been evolved to become the standard adopted in Substation Automation Systems. Among its various aspects it can be highlighted the real-time services, which allows the implementation of automation and protection functions within the substation by exchanging specific messages between Intelligent Electronic Devices via a digital data bus network. The main objective of this text is to explore some issues about the implementation of one class of real-time services: the transmission of sampled values through SMV Services, defined by IEC 61850-9 Standard. First, it is presented a brief summary of the main features of IEC 61850 Standard which allows it to meet the three main requirements on this standard: interoperability between devices from different manufacturers, versatility in configuration and reconfiguration of Substation Automation System, and possibility of implementation of new technologies. Next, it is explored, with more details, all aspects involved in the implementation of SMV Services. Due to the complexity of this subject, the author proposes approaches it from the perspective of five interdependent topics: variations of IEC 61850-9 Standard, process bus reliability, time synchronism, analysis of measurement quality, and cyber security. Based on results presented two platforms are proposed, an Optical Voltage Transformer prototype and a Differential Protection Relay prototype for power transformers, in order to explore some of aspects related to the implementation of a process bus according to IEC 61850-9 Standard. It was executed also some tests of generation and transmission of messages containing samples values of voltage/current from power system (referred as SV Messages) in order to implement them in fact, and to evaluate available market tools. At the end it is propoused a model for simulation of power system and network communication using Matlab/Simulink software. The author hopes this work may contribute to clarify the various concepts involved in the implementation of a process bus according to IEC 61850-9 Standard, aiding in research and development of new tools and devices, and improvement of IEC 61850 Standard.

Made available in DSpace on 2016-08-17T14:52:58Z (GMT). No. of bitstreams: 1 Raimundo Nonato Rosa Filho.pdf: 1125835 bytes, checksum: 91689e7b58443f6d0eb73d752860ce37 (MD5) Previous issue date: 2005-03-31 / In this work a methodology for reduction of maintenance cost in the on-load tap changers (OLTC) of extra high voltage is proposed. The methodology is based on the use of Artificial Neural Networks (ANN) for the intelligent processing of input signals of the commutator. The neural nets adequately trained allow to create an information system and dedicated diagnosis of the OLTC. This system can interpret and diagnosis the components through the real time input signals in order to delay the power transformer maintenance intervals, foreseeing when the OLTC is going to maintenance have intervention based on its condition. It has been adopted a multiperceptron ANN architecture in which the input vector has 22 components and the output considers only one component with the status of the OLTC condition in function of its operation time. This output information is used to determine the periods of maintenance of the commutators. It is reported an application of the proposed system considering the on load tap changer of an autotransformer bank of 500/230/13.8 kV, 600MVA of Centrais Elétricas do Norte do Brasil S/A (ELETRONORTE). The results indicate the advantages of the maintenance based on the condition using ANN. / Neste trabalho é proposta uma metodologia para redução de custo de manutenção nos comutadores de tap sob carga (OLTC) dos transformadores de potência de extra alta tensão. A metodologia está baseada na utilização de redes neurais artificiais (RNA) para o processamento inteligente dos sinais de entrada dos comutadores. As redes neurais adequadamente treinadas permitem criar um sistema de informação e diagnóstico dedicado a OLTC que podem interpretar e diagnosticar os componentes através das entradas em tempo real de forma a, postergar os intervalos de manutenção, prevendo quando o OLTC deverá sofrer intervenção de manutenção baseada na condição do OLTC. Foi adotada uma arquitetura de RNA de multiperceptron na qual a entrada considera um vetor com 22 entrada e apenas uma saída com o status da condição do OLTC em função do tempo de operação. Essa informação de saída é utilizada para determinar os períodos de manutenção dos comutadores de tap. É realizada uma aplicação do sistema proposto considerando o comutador de tap sob carga de um banco de autotransformador de 500/230/13.8kV, 600MVA da Centrais Elétricas do Norte do Brasil S/A( ELETRONORTE) e os resultados indicam as vantagens da manutenção baseada na condição usando RNA.

In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be tested. In this thesis a time-domain transformer model is presented. The model includes core losses as magnetic static hysteresis, eddy current and excess eddy current losses. Moreover, the model comprises winding losses including eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a total transformer model. This results in a detailed transformer model. One important result of the thesis is the possibility to simulate dynamic hysteresis including the eddy current shielding in the magnetic core material. This is achieved by using Cauer circuit combined with analytical expression for static and dynamic hysteresis. Thereby, all magnetic loss components in the material can be simulated accurately. This dynamic hysteresis model is verified through experiments showing very good agreement. / QC 20101116

This master thesis investigates a redesign for a maintenance tube, used for both sampling and draining transformer oil from a tap changer compartment. With the current design, one can do one or the other of sampling and draining. The effect of this on a transformer site during maintenance means that personnel must bring extra equipment to do the maintenance routine. Along with the extra equipment, it also involves climbing the transformer an extra time to place the equipment for draining. The project aims to address several issues in the context of the product. Redesigning the product to reduce maintenance time, and therefore downtime and electrical outages. Reducing the number of times that the transformer housing needs to be climbed in order to perform maintenance work. This with the purpose of improving working environment for maintenance personnel. With the new design of the maintenance tube, draining and sampling can be done with the same pipe without the need for extra equipment. This is through a mechanism in the tube which allows the personnel to choose whether to drain oil from the bottom of the container or to take oil samples from an area in the tap-changer housing which gives more accurate results. The function of the mechanism can be described in the same way as a pen, where if you push the button, a tube will extract itself and close of the sampling inlets, enabling draining from the bottom. Push the button again and the same tube will retract, allowing you to take samples from the appropriate area again. The new design also adheres to the dimensional requirements needed for the design to fulfil the additional functions the tube has. The project results in a design which would not only fill requirements of functions but also preserves some of the previous parts along with their interfaces. This means that the new design could be installed on current versions of tap-changer models when the next service interval is due.

Vibrations are everywhere around us all the time and we often recognise them as sounds that we can hear and analyse with our brain. In this thesis, data that has been gathered from a diverter switch (DS) in a controlled environment, is analysed. This data consists of vibroacoustic measurements and information to indicate what is happening inside the DS as the vibroacoustic data is gathered. The frequency properties of vibroacoustic data from the DS gathered before this thesis are displayed using a wavelet transformation model. This means the frequency properties of the signal can be approximated for all times in the operation with a certain accuracy. As the DS is built from many different components, the frequency properties of these components are compared to the time-frequency picture of the full DS operation. This sort of comparison ends up not being feasible as the complexity of the DS frequency pattern is much more than that of a sum of its component’s frequency pattern. A second approach of analysing the gathered vibroacoustic data is by using a classification model. The information about what is happening inside of the DS is used to train a logistic regression model on different defined regions of the vibroacoustic data. Before the training is preformed though, the different defined regions are transformed into frequency space with help of the fast Fourier transform. With this, a classification model is produced, where vibroacoustic data of any time region can be fed into the model and the model will classify which defined region this vibroacoustic data belongs to. The results are promising, and the model can be used both for classification of the defined regions and potentially used to determine if the vibroacoustic properties of the DS has changed due to wear of the mechanical components or transformer oil.