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.

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.

Methane-based rocket propellant is gaining traction as a green technology with advantages in sustainability, cost-effectiveness, and performance. However, under high temperatures found in rocket nozzle cooling channels, methane can undergo thermal decomposition known as methane pyrolysis, resulting in the generation of hydrogen and solid carbon. This poses challenges to rocket engine performance and can eventually cause engine failure. Understanding and predicting the composition of evolved gases in rocket engine processes is therefore crucial. This thesis focuses on quantifying the production of hydrogen in the exhaust stream. To achieve this objective, a correlational measurement method utilizing sensors was developed and experimentally investigated. This approach involved the detailed mapping of sensor responses to variations in gas composition, temperature, and pressure, which were compared and validated against theoretical data derived from REFPROP; a widely used software tool for calculating gas properties. The sensors employed in this study enabled direct measurements of the speed of sound (SOS) and thermal conductivity (TCD) of the gas. The SOS measurements exhibited strong agreement with theoretical predictions in response to changes in hydrogen content. In contrast, the TCD measurements showed lower sensitivity to hydrogen. It was observed that temperature exhibited a substantial influence on both SOS and TCD compared to pressure. However, the implementation of experimental and theoretical correction coefficients effectively compensated for these effects. The resulting calibration curves demonstrated an absolute deviation of 0.2-0.3%vol in hydrogen concentration, which demonstrates the effectiveness of the developed method of quantifying hydrogen in gas mixtures. Lastly, the occurrence of methane pyrolysis was tested and confirmed. / Metan-baserat raketbränsle är en attraktiv grön teknologi med fördelar inom hållbarhet, kostnadseffektivitet och prestanda. Dock kan metan vid höga temperaturer funna i kylningskanalerna av raketmunnstycken undergå termisk sönderfallning via en process som kallas för metanpyrolys, vilket resulterar i produktionen av vätgas och fast kol. Detta medför utmaningar för prestandan av raketmotorn och kan i slutändan förstöra motorn. Det är därför mycket viktigt att kunna förstå och förutsäga sammansättningen av de gaser som bildas i processerna i raketmotorer. Detta examensarbete fokuserar på att kvantifiera produktionen av vätgas i avgasströmmen. För att uppnå detta mål utvecklades och experimentellt undersöktes en korrelationsmätmetod som använder sensorer. Detta tillvägagångssätt innebar en detaljerad kartläggning av sensorernas svar på variationer i gassammansättning, temperatur och tryck, som sedan jämfördes och validerades mot teoretiska data från REFPROP; ett välkänt programverktyg för beräkningen av gasegenskaper. De sensorer som användes i denna studie möjliggjorde direkta mätningar av ljudhastigheten (SOS) och värmeledningsförmågan (TCD) hos gasen. SOS-mätningarna visade en stark överensstämmelse med teoretiska förutsägelser som svar på förändringar i vätgasinnehållet. TCD-mätningarna visade däremot lägre känslighet för väte. Det observerades att temperaturen hade en betydande inverkan på både SOS och TCD jämfört med trycket. Implementeringen av experimentella och teoretiska korrigeringskoefficienter kompenserade dock effektivt för dessa effekter. De resulterande kalibreringskurvorna visade en absolut avvikelse på 0.2-0.3%vol i vätgaskoncentration, vilket betonar effektiviteten hos den utvecklade metoden för att kvantifiera väte i gasblandningar. Slutligen testades och bekräftades förekomsten av metanpyrolys.

In dieser Arbeit wurden zwei Messaufbauten für die online Gasanalyse von elektrochemischen Reaktionen entwickelt und im Hinblick auf ihre Unterschiede und Gemeinsamkeiten sowie auf den Designprozess im Allgemeinen verglichen: Differenzielle elektrochemische Massenspektrometrie (DEMS) zur Untersuchung von Nebenreaktionen in Natriumionenbatterien (SIBs). Verschiedene Designansätze aus der Literatur wurden verglichen, um den für die Anwendung in SIBs am besten geeigneten zu finden. Danach wurde ein selbst entwickeltes Design implementiert und validiert. Für die Datenauswertung wird ein neuartiger Ansatz für DEMS in Alkaliionenbatterien vorgestellt, der eine interne Validierung der Ergebnisse ermöglicht. Eine Zusammenfassung der Literatur über bekannte Reaktionen, die zur Gasbildung in Alkali-Ionen-Batterien führen, wird als Referenz die Gasentwicklung in den in dieser Arbeit untersuchten Materialien herangezogen. Das System wird zur Messung der Gasentwicklung verschiedener Elektrodenmaterialien in Halbzellenkonfiguration und zur Bewertung des Zusammenspiels einiger Elektroden in Vollzellenkonfiguration verwendet. Bei den untersuchten Materialien handelt es sich um: Natrium-Mangan-Nickeloxid (NaMNO), Natrium-Vanadium-Phosphat (NVP), Preußisch Weiß (PW), Graphit und Hartkohlenstoff. Als Elektrolyte wurden überwiegend 1M NaPF6 in Diglyme (2G), bzw. Propylencarbonat (PC) verwendet. Das zweite System ist eine rotierende Scheibenelektrode in Verbindung mit Gaschromatographie (RDE-GC). Es wurde entwickelt, um kinetische Effekte bei der elektrokatalytischen CO2-Reduktion an Kupferelektroden zu untersuchen. Die Korrelation von Massentransporteigenschaften und der Gasproduktanalyse kann Aufschluss über die Massentransportabhängigkeit von Selektivität und Aktivität der Reaktion geben. Hier wird die Gasanalyse genutzt, um die elektrochemischen Daten in Teilstromdichten zu dekonvolutieren, die unter definierten Stofftransportbedingungen zur Bildung verschiedener Produkte führen. / In this thesis two independent measurement setups for online gas analysis, in electrochemical reactions are developed and compared in terms of their differences and similarities and on the design: Differential electrochemical mass spectrometry (DEMS) for the investigation of side reactions in sodium-ion batteries (SIBs). Different design approaches from literature are evaluated to find the most suitable for the application in SIBs. After that a custom design is implemented and validated. A novel approach to DEMS in alkali-ion batteries for the data evaluation is presented, that enables internal verification of the results. Known reactions that lead to gas formation in alkali-ion batteries are reviewed form the literature, as a reference to discuss the gas evolution found in materials investigated. The system is used to measure the gas evolution of different electrode materials in half-cell configuration, and to evaluate the interplay of some of the electrodes in full-cell configuration. Materials that are studied are: sodium manganese nickel oxide (NaMNO), sodium vanadium phosphate (NVP), prussian white (PW), graphite and hard carbon. To do that two model electrolytes were selected 1M NaPF6 in diglyme (2G) and propylene carbonate (PC). The second system is a rotating disc electrode coupled with gas chromatography (RDE-GC). It is designed to study kinetic effects on the electrocatalytic CO2 reduction (CO2RR) on copper electrodes. The correlation of defined mass transport properties and gas product analysis can give insight into the mass transport dependencies on the selectivity and activity of the reaction. Here the gas analysis is used to deconvolute the electrochemical data into partial current densities, that lead to the formation of different products, under defined mass transport conditions. While some challenges remain, preliminary data that underlines the capability of such system as well as the findings on how to design such a system are presented.

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This master´s thesis deals with the properties of gel polymer electrolytes, brief characteristics of other types of electrolytes and materials that are used for preparing polymer electrolytes. The thesis explains the use of the gel electrolytes in practice, the current conduction in the electrolytes and the properties of ionic liquids, and flame retardants. This thesis also focuses on methods of measurement of mechanical properties of gel polymer electrolytes. The practical part is focused on preparation of methacrylate gel electrolytes and their modifications with the use of flame retardant - triethyl phosphate (TEP) and ionic liquid - 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Emim TFSI). In this part there are evaluations of their potential funcionality (potential window) and specific conductance conductivity using the method LSV (linear sweep voltammetry) and impedance spectroscopy. The practical part also includes a thermal analysis of selected samples by TGA, DTA and EGA methods.

Acid maltase deficiency (AMD) is a rare autosomal recessive genetic disorder that results in an accumulation of glycogen in the lysosomal storage vacuoles. It is classified as a glycogen storage disease (type II) and is also known as Pompe's disease. The prognosis of the patient with AMD is poor and the main cause of death is respiratory failure. We report a female patient whose respiratory insufficiency was documented to occur most severely during rapid eye movement sleep and who benefited clinically from the institution of nocturnal noninvasive bilevel positive airway pressure.