This master’s thesis is dealing with low frequency all valve stereo amplifier unit conception for an electric guitar. The amplifier contains two independent output stages with two power tubes EL34, working in AB class, with 40Watts of power. The apparatus is equipped with two channels, EQ correctors, parallel effects loop, output selection with lowered anode power supply, selection between silicon or tube rectifier. The preamplifier works in mono mode and the stereophony is reached by dividing the signal in an added effects system. This unusual solution differs from both monaural conceptions and binaural power amplifiers which contains no preamp. It offers the possibility of stereophony without the necessity of dividing the guitar signal before the amplifier’s input. The sound that comes from the speaker on one side is effected and on the other side is dry by using monaural effects apparatus. The sound from both speakers is effected by using binaural effect apparatus. The amplifier can be used as power amplifier stage only when the return of the effect loop is used as the amplifier input. Every available possible solution is discussed in case of each block and then the most suitable is chosen. The biggest attention is paid to a proposal and calculation of both power and output transformer, ergonomical lay-out of the stages in need of the best S/N separation. The stages were simulated in Micro-Cap 9.0 and Tonestack 1.3 computer programmes. The construction was carried out with the emphasis on proper shielding and grounding. The overall stability tests were performed after building the amplifier as well as frequency characteristics with the scope and distortion with the distortion meter.

The present thesis deals with power transformers, oil and dry, their properties and structures, and subsequently faults that occur in oil transformers. First, the disorders discussed in general and then a comparison of individual samples transformer failures that have occurred in recent years in the Moravian-Silesian and Olomouc regions. Finally, I analyze the failures and the most common encountered, I suggested solutions to reduce their incidence.

Les Transformateurs Moyenne Fréquence (TMF) sont une technologie innovante par rapport aux transformateurs basse fréquence, avec la promesse d’une réduction de volume et d’une augmentation du rendement. Cette thèse s’intéresse en particulier à leur conception pour des applications haute tension forte puissance, telles que les réseaux haute tension et moyenne tension à courant continu, ainsi que les réseaux ferroviaires. Dans ces applications, les TMF sont utilisés au sein de convertisseurs pouvant générer des contraintes spécifiques à prendre en compte durant leur conception : signaux non-sinusoïdaux, tension de polarisation, valeurs d’inductances cibles. De plus, les choix technologiques actuellement disponibles pour la réalisation des TMF sont nombreux, et aucun de ces choix ne fait actuellement consensus quelle que soit l’application visée. Des tendances ont pu être identifiées à l’aide d’un outil de classification des designs de TMF issus de la littérature. Ainsi, les technologies les plus prometteuses ont été sélectionnées et retenues pour la suite. A partir de ces technologies, une méthodologie de conception permettant de concevoir et comparer rapidement et ce de façon semi-automatique des TMF avec différents choix technologiques a été mise en place. Elle est constituée de trois étapes : pré-design, design analytique et validation. Le design analytique complet du TMF avec différents choix technologiques est réalisé à l’aide d’un outil de conception automatisée développé durant cette thèse, que nous avons nommé SUITED (SUpergrid Institute TransformEr Design). Cette méthodologie requiert des modèles et données pour chacun des composants et phénomènes du TMF. Concernant le noyau magnétique, une revue et une sélection de modèles issus de la littérature ont été effectuées pour l’évaluation de l’inductance magnétisante et des pertes magnétiques. De plus, des caractérisations magnétiques ont permis de mettre en évidence l’impact de certains procédés technologiques sur les niveaux de pertes de noyaux magnétiques en matériau nanocristallin, qui est un excellent candidat pour les TMF. Au niveau des bobinages, des modèles analytiques pour calculer le champ magnétique, l’inductance de fuite et les effets de peau et de proximité ont été développés et comparés avec ceux de la littérature ainsi que des simulations. Ces nouveaux modèles s'avèrent obtenir une meilleure précision sur les géométries de TMF considérées que ceux de la littérature. De plus, une nouvelle méthode d’évaluation des capacités parasites de bobinages à spires rectangulaires a été mise en place et validée avec succès. Des schémas thermiques équivalents ont été identifiés pour différentes géométries de TMF. Les résistances thermiques de conduction, convection et radiation sont calculées à partir de modèles détaillés. En particulier, l’anisotropie des matériaux est prise en compte pour la conduction thermique, et les coefficients de convection sont évalués via des corrélations différentes pour chaque face du TMF. Les schémas thermiques sont ensuite résolus de façon itérative et analytique pour prendre en compte les non-linéarités des résistances thermiques tout en optimisant le temps de calcul nécessaire. Enfin, l’ensemble de la méthodologie de conception mise en place a été appliqué sur trois cas d’études correspondant à des applications cibles : haute tension, moyenne tension et ferroviaire. Les résultats obtenus montrent effectivement la performance et la nécessité de cette approche / Medium Frequency Transformers (MFT) are an innovative technology compared to low frequency transformers, with the promise of reduced volume and increased efficiency. This PhD thesis focuses in particular on their design for high voltage, high power applications, such as high voltage and medium voltage DC networks, as well as railway networks. In these applications, MFTs are used in converters that can generate specific constraints to be taken into account during their design: non-sinusoidal signals, polarization voltage, target inductance values. Moreover, the technological choices currently available for the realization of MFTs are numerous, and there is currently no consensus on any technology for any given application. Trends could be identified using a tool to classify MFT designs from the literature. Thus, the most promising technologies were selected and retained for the future. Based on these technologies, a design methodology was developed to quickly and semi-automatically design and compare MFTs with different technological choices. It consists of three steps: pre-design, analytical design, and validation. The complete analytical design of the MFT with different technological choices is carried out using an automated design tool developed during this thesis, named SUITED (SUpergrid Institute TransformEr Design). This methodology requires models and data for each of the components and phenomena of the MFT. Concerning the magnetic core, a review and selection of models from the literature were carried out for the evaluation of the magnetizing inductance and magnetic losses. In addition, magnetic characterizations have made it possible to highlight the impact of certain technological processes on the levels of loss of magnetic cores made of nanocrystalline material, which is an excellent candidate for MFTs. Concerning the windings, analytical models to calculate the magnetic field, leakage inductance and skin and proximity effects were developed and compared with those in the literature and simulations. These models are proving to be more accurate on the MFT geometries considered. On top of that, a new method for evaluating the parasitic capacitances of windings with rectangular turns has been successfully implemented and validated. Thermal networks have been identified for the different MFT geometries. The thermal resistances of conduction, convection and radiation are calculated from detailed models. In particular, the anisotropy of materials is taken into account for thermal conduction, and the convection coefficients are evaluated via different correlations for each face of the MFT. The thermal networks are then solved iteratively and analytically to take into account the non-linearity of the thermal resistances while optimizing the required computation time. Finally, this entire design methodology was applied to three case studies corresponding to the target applications: high voltage, medium voltage and rail. The results obtained do show the performance and necessity of this approach.

Hitachi ABB Power Grids is a world leading manufacturer of power transformers, operating on an increasingly competitive market. With the advancements in digitalization and electrification, the production of power transformers has been subject of higher demands, both in terms of product quality and production efficiency. To stay ahead of market rivals, constant development of the business and its production processes is necessary, which has been enabled by increased access to innovative technical solutions. Novel appliances and areas of development has been investigated, of which 3D-scanning is one of the promising technologies that has proven useful in the manufacturing industry.  The purpose of this study has been to map the production process of power transformer manufacturing at Hitachi ABB Power Grids, with the intention of identifying potential areas for use of 3D-scanning technology in quality management. By analyzing each individual production segment, the study has sought to answer to where in the production system that 3D-scanning technology can be beneficial, what type of improvements it can contribute with, and what risks and limitations that using the technology might entail.  The results were obtained by analyzing empirical data, collected through both qualitative and quantitative methods. Interviews with employees and on-site observations has been the main sources of data, together with documentation and statistics from the company’s own data bases.  Central factors that the analysis was built upon are the registered costs of failure and reported quality defects, combined with the appropriateness of 3D-scanning technology in each segment regarding the practical usability, advantage in time, economic profitability, and the feasibility of implementation in the production system. A value assessment was made of the device’s potential, leading to identifying improvements in transparency, traceability, and efficiency. Some of the discussed drawbacks were limited visual access, faulty handling of the equipment, and excessive reliance on the technology. / Hitachi ABB Power Grids är en världsledande tillverkare av krafttransformatorer, agerandes på en alltmer konkurrensbenägen marknad. Med digitaliseringens och elektrifieringens framfart ställs högre krav på produktionen av krafttransformatorer, både gällande produktkvalitet och produktionseffektivitet. För att bibehålla en ledande position krävs därför ständig utveckling av verksamheten och dess processer, vilket bland annat möjliggjorts av den ökade tillgången till innovativa tekniska lösningar. Nya verktyg och förbättringsområden undersöks, varpå en av de uppmärksammade teknikerna är 3D-skanning, vilket visat sig användbart inom tillverkningsindustrin.  Syftet med studien har varit att kartlägga processen för krafttransformatortillverkning hos fallstudieföretaget Hitachi ABB Power Grids, med avsikt att identifiera möjligheterna kring användning av 3D-skanningsteknik i kvalitetsarbetet. Genom att undersöka varje individuellt delmoment i produktionsprocessen har studien sökt besvara var i produktionssystemet som 3D-skanningstekniken kan medföra förbättringar, vilken typ av förbättringar som kan åstadkommas, samt de risker och begränsningar som användning av tekniken eventuellt kan medföra.  Resultaten erhölls genom analys av empiriska data som samlats in genom både kvalitativa och kvantitativa metoder. Intervjuer med personal och observationer på anläggningen har utgjort de huvudsakliga källorna till information, tillsammans med dokumentation och statistik från företagets interna databaser.  Centrala faktorer som analysen har byggt på är produktionens registrerade felkostnader och rapporterade kvalitetsfel, i kombination med 3D-skanningsteknikens lämplighet för respektive avsnitt gällande praktisk användbarhet, tidsmässig fördel, ekonomisk lönsamhet och implementerbarhet i produktionssystemet. En värdering gjordes därefter av teknikens potential, och förbättringar i form av transparens, spårbarhet och effektivitet kunde identifieras. Några av de brister som uppmärksammades var begränsad visuell åtkomst, felaktig manövrering av utrustningen och överdriven tillförlitlighet till tekniken.

Mälarenergi’s vision is a world where we live and operate together without climate impact. This degree project has examined which opportunities Mälarenergi Elnät has in order to work towards this vision by looking more closely at whether their bigger substations can become self-sufficient in terms of heating, cooling and battery charging. The purpose of this degree project was to investigate how heat recovery from the substations’ transformers and the installation of PV-systems could contribute to both more environmentally friendly and self-sufficient substations. In addition to that, the economics and how this would affect the Swedish power grid regulation were of interest. The thesis was based on current values and data for oil temperatures and installed power in three of Mälarenergi Elnät’s substations. In addition to this, the thesis also includes a literature study, where previous research in heat transfer from power transformers, up-to-date information about PV-installations and the power grid regulation in Sweden were studied. The results of the thesis showed that both PV-installations and heat exchange for heating the station buildings could be of great benefit for Mälarenergi Elnät. In all but one case, the energy saving measures resulted in lower life cycle costs than if no measures were taken. It shows that the measures investigated in the thesis are not only good from an environmental perspective, but also has economic profitability.

An electrical bushing is one of the most important elements in a power transformer. Steep front surges such as transient impulse voltage from lightning strikes is an inevitable electromagnetic transient mostly happening in power transmission and distribution system. The bushing might lead to be degraded due to such kind of surge. This project deals with overvoltage stress distribution on the transformer bushing under the effect of electromagnetic transient response such as lightning impulse.  To understand the behavior of transient response on the bushing, a proper model of power transformer bushing is built-in Comsol multiphysics to authenticate the stress distribution. The electromagnetic wave of impulse propagates onto the overhead line that connects with the transformer. Some understanding of the transient behavior of a conductor bushing has been achieved through studying the influence of inductance property and the skin effect characteristics of a multi-layer coaxial cable on the wave propagation, which has been structured in this project to simplify the model. On the other hand, the skin effect analysis on the conductor of the bushing has been taken also into account in this project using real conductor simulation in the Comsol model. Thus, it will be interesting to compare the real conductor model with the perfect conductor of the bushing through analyzing the current density effect on it.  In this project, multi-layer of coaxial cable and transformer bushing are simulated. The simulation is carried out for time domain and frequency domain in Comsol based on the model characteristics. / En elektrisk genomföring är ett av de viktigaste elementen i en transformator. Spänningsvågor med branta fronter som impulsspänningar från blixtnedslag är ett oundvikligt elektromagnetiskt övergående fenomen som oftast sker i kraftöverförings- och distributionssystem. Genomföringen kan leda till att degraderas på grund av en sådan våg. Detta projekt handlar om fördelning av överspännings på transformatorgenomföringen under påverkan av elektromagnetisk transient respons, såsom blixtimpuls.  För att förstå beteendet hos övergående respons på genomföringen är en korrekt modell av transformatorgenomföring inbyggd Comsol-flerfysik för att autentisera spänningsfördelningen. Den elektromagnetiska impulsvågen fortplantas från luftledningen som ansluter till transformatorn. Viss förståelse för det övergående beteendet hos en ledargenomföring har uppnåtts genom att studera påverkan av induktansegenskaper och hudeffektegenskaperna hos en flerskikts koaxialkabel på vågutbredningen, vilket har strukturerats i detta projekt för att förenkla modellen. Å andra sidan har hudeffektanalysen på genomföringens ledare beaktats i detta projekt med användning av verklig ledarsimulering i Comsol-modellen. Således blir det intressant att jämföra den riktiga ledarmodellen med den perfekta ledaren för genomföringen genom att analysera strömtäthetseffekten på den.  I detta projekt simuleras flerskikt av koaxialkabel och transformatorgenomföring. Simuleringen utförs för tidsdomän och frekvensdomän i Comsol baserat på modellegenskaperna.

Transients encountered by transformers in power stations during normal operation can have complex oscillatory overvoltages containing a large spectrum of frequency components. These transients can coincide with the natural frequencies of the transformers windings, leading to voltages that can be greater or more severe than the current factory proof tests. This may lead to insulation breakdown and catastrophic failures. Existing lumped parameter RLCG transformer models have been proven to be less accurate for very fast transient overvoltages (VFTO) with frequencies over 1 MHz. A white box model for transient analysis of transformer windings has been developed using Multiconductor Transmission Line (MTL) Theory. This model enables the simulation of natural frequencies of the transformer windings up to frequencies of several MHz, and can be used to compute voltages between turns by representing each turn as a separate transmission line. Both continuous and interleaved disk windings have been modelled and a comparison and validation of the results is presented. / May 2017

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.

Cette thèse de doctorat traite des méthodes d’évaluation de l’état des transformateurs de puissance à huile. Elle apporte une approche particulière de mise en oeuvre des méthodes de classification dans la fouille de données. Elle propose une stratégie qui met en oeuvre deux nouveaux indicateurs de santé de l’huile construit à partir d’un système neuro flou ANFIS (Adaptative Neuro-Fuzzy Inference System) et un classifieur ou prédicteur de défaut construit à partir des méthodes de classification supervisée, notamment le classifieur Bayésien naïf. Un organigramme simple et efficace d’évaluation de l’état des transformateurs y est proposé. Il permet de faire une analyse rapide des paramètres issus des analyses physico-chimiques de l’huile et de des gaz dissous. Une exploitation des méthodes de classification non supervisée, notamment les méthodes de k-moyennes et C-moyennes flous a permis de reconstruire les périodes de fonctionnement d’un transformateur marquées par des défauts particuliers. Il a aussi été démontré comment ces méthodes peuvent servir d’outil d’aide à l’organisation de la maintenance d’un groupe de transformateurs à partir des données d’analyses d’huile disponibles. / This PhD thesis deals the assessment method of the state of power transformers filled with oil. It brings a new approach by implementing classification methods and data mining dedicated to transformer maintenance. It proposes a strategy based on two new oil health indicators built from an adaptive Neuro-Fuzzy Inference System (ANFIS). Two classifiers were built on a labeled learning database. The Naive Bayes classifier was retained for the detection of fault from gases dissolved in oil. A simple and efficient flowchart for evaluating the condition of transformers is proposed. It allows a quick analysis of the parameters resulting from physicochemical analyzes of oil and dissolved gases. Using unsupervised classification techniques through the methods of kmeans and fuzzy C-means allowed to reconstruct operating periods of a transformer, with some particular faults. It has also been demonstrated how these methods can be used as tool to help the maintenance of a group of transformers from available oil analysis data.

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.