Master of Science

Le SF6 (Hexafluorure de soufre) a été utilisé depuis longtemps comme un gaz d'isolation très adapté pour les appareillages électriques. Cependant, son impact sur le réchauffement climatique, estimé 24000 fois plus actif que le CO2 sur 100 ans, pose le problème de son remplacement à moyen terme. L'objectif de cette thèse est d'étudier deux solutions de remplacement du SF6 : les liquides biodégradables et les mélanges de gaz CF3I/N2. Les deux phénomènes physiques conduisant à un claquage : la génération d'une décharge et sa propagation, ont été étudiés séparément. L'influence des différents paramètres tels que la pression, distance, distribution de champ, teneur en particules ou humidité relative…a été également mise en évidence. La fonction d'isolation est en fin validée dans un maquette disjoncteur moyenne tension qui représente un cas d'application réelle. / SF6 gaz (sulfur hexafluoride) has been widely used as a very suitable insulation material for HV apparatus. However, it is also known as a remarkable green house gas, which Global Warming Potential is 24000 times greater than CO2. Consequently, its utilisation in the electrical industry should be reduced. The aim of this work is to study two alternatives to SF6: biodegradable liquids and CF3I/N2 gas mixtures. The two physical phenomena leading to a breakdown: the generation of a discharge and its propagation have been studied separately. The influence of various parameters such as pressure, distance, field distribution ,particle content and relative humidity ... was also highlighted. The insulation function is then validated in a MV circuit breaker, which represent a real application case.

Este trabalho tem como foco principal apresentar os resultados e as contribuições da pesquisa experimental comparativa de subcoberturas em sistemas de cobertura. Para tal fim foram utilizados quatro protótipos localizados no canteiro experimental do CRHEA - EESC em São Carlos, São Paulo. Os protótipos foram construídos da mesma forma e com os mesmos materiais: tijolo comum, laje cerâmica recapeada com concreto; cobertos com telhas de fibrocimento e submetidos às mesmas excitações de clima ao ar livre. A análise foi feita aplicando um curto intervalo de clima, com respaldo teórico da climatologia dinâmica. Um dos protótipos serviu como testemunho e não recebeu a instalação de nenhuma subcobertura. Os outros três receberam cada um, respectivamente, subcobertura de foil (isolante por reflexão, ou barreira de radiação), lã de rocha (isolante convencional, condutividade térmica k) e de caixas cartonadas Tetra Pak, um resíduo, como isolante por reflexão e câmara de ar, já que foram utilizadas fechadas e uma ao lado da outra. Foram monitoradas as temperaturas superficiais da telha e da laje e, das temperaturas de bulbo seco no ático e na parte interna dos protótipos a 1,10 m de altura. As medidas de aquisições de dados foram feitas através de CR10X Campbell Scientific automático com medições em 30 segundos, armazenados e totalizados em 30 minutos, o que resultou em valores de clima ao livre e em recinto fechado muito precisos. / Thermal comfort achievement can be done by using thermal reflexive barriers, meaning energy savings and avoiding health problems of air conditioning. It can also be done by using building construction waste materials as Tetra Pak boxes, a low cost reflexive insulation, and applying an industrial \"foil\" which the same effect on reducing indoor air temperatures. In the same way traditional thermal insulation materials were used on this research as the mineral wool (conventional insulation material, thermal conductivity - k values). The analysis was made applying short intervals of climate such as recommended by the dynamic climatic approach. The use of foil insulation can be justified because of its behavior as a reflective barrier and because it has a lot of acceptation; mineral wool (mineral source with low k insulation values) for being a traditional kind of thermal insulation and the Tetra Pak box, because it is a reflective insulation and also because of its waste recycle usage characteristic. The research shows the insulation thermal efficiency applied on three kinds of fiber asbestos cover system, which makes the indoor air temperatures inside of comfort zones values, as intended to expose by graphics, made by real time and automatic experimental measurements. The measurements of data acquisitions were made by automatic CR10X Campbell Scientific Inc., 30 seconds scanner and totalized storage as 30 minutes average intervals. This means a very accurate result of values of outdoor and indoor climate translated by indoor and out door air temperatures.

No description available.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1943. / Includes bibliographical references (p. 83-84).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1943. / Includes bibliographical references (p. 79-80).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1943. / Includes bibliographical references (p. 88-89).

Στην παρούσα εργασία ασχοληθήκαμε με τα ηλεκτροτεχνικά υγρά, τόσο θεωρητικά όσο και πειραματικά. Σε θεωρητικό επίπεδο περιγράφουμε το ρόλο των μονωτικών λαδιών, τις χρήσεις τους, τις ιδιότητές τους και τους παράγοντες που τα επηρεάζουν. Σε πειραματικό επίπεδο, πραγματοποιούμε πλήθος μετρήσεων με στόχο την εξακρίβωση και την εξαγωγή συμπερασμάτων από την εφαρμογή γραμμικώς αυξανόμενης a.c. τάσης πάνω σε δύο διαφορετικά είδη μονωτικών λαδιών. / As networks of High Voltage Alternate Power can be characterized those who function in voltage higher than 1000V. Therefore, the electrological equipment which is going to be settled and function in alternate power voltage higher than 1KV is characterized as a High Voltage Equipment. The insulation of the equipment and that of the high voltage establishments is indispensable in order to maintain the potential difference between the under high voltage conductible parts. Alongside its main destination, insulation may have other roles too such as the mechanic support of the wire way, the exchange of temperature e.c.t. In the present project we dealt with the electro – technical liquids in theoretical and also in experimental level. According to the theoretical level, we described the role of the insulating oils, their uses, their attributes and the factors that affect them. According to the experimental level we accomplished a number of measurements, having as intension the verification and the deduction of conclusions coming from the application of the linearly ongoing a.c. voltage on two different kinds of insulating oils. From the aforementioned measurements we noticed the impact that the length of the gap, the temperature, even the combination of the two different insulating oils have on the tendency in breaking not only quantitavely (change of size) but also qualitatively (change of statistical attributes). For carrying out the experimental procedure we utilized the device of the High Voltages Laboratory’s electrological equipment. All measurements and also the selection of the appropriate testing prescription were done by this device, taking each time the necessary safeguards for us and for the lab’s facilities. Finally, the results were gathered in billboards and were farther analyzed according to indispensable diagrams for the deduction of conclusions. In this point is very important to mention that on those billboards is indicated the average value which refers to the tendency in breaking and that of typical variations, just for practical reasons.

Η μόνωση του εξοπλισμού και των εγκαταστάσεων υψηλής τάσης είναι απαραίτητη προκειμένου να διατηρηθεί η διαφορά δυναμικού μεταξύ των υπό υψηλή τάση αγώγιμων μερών. Παράλληλα με τον κύριο προορισμό της, η μόνωση μπορεί να έχει και άλλους ρόλους, όπως η μηχανική στήριξη των αγωγών, η ανταλλαγή θερμότητας κ.ά. Στην παρούσα εργασία ασχοληθήκαμε με τα ηλεκτροτεχνικά υγρά τόσο θεωρητικά όσο και πειραματικά. Σε θεωρητικό επίπεδο, περιγράφουμε το ρόλο των μονωτικών λαδιών, τις χρήσεις, τις ιδιότητες τους και τους παράγοντες που τα επηρεάζουν. Σε πειραματικό επίπεδο πραγματοποιούμε πλήθος μετρήσεων με στόχο την εξακρίβωση και την εξαγωγή συμπερασμάτων, χρησιμοποιώντας τη συσκευή Baur Oil Tester DTA 822-129-1 του ηλεκτρολογικού εξοπλισμού του εργαστηρίου υψηλών τάσεων. Όλες οι μετρήσεις καθώς και η επιλογή της κατάλληλης προδιαγραφής των δοκιμών έγιναν από τη συσκευή αυτή, λαμβάνοντας κάθε φορά τα αναγκαία μέτρα προστασίας για μας και την εγκατάσταση του εργαστηρίου. Το μονωτικό έλαιο που χρησιμοποιούμε είναι ο φυσικός εστέρας Envirotemp® FR3™, από την εταιρεία COOPER PowerSystems. Μερικοί από τους παράγοντες που εξετάστηκαν είναι το μέγεθος του διακένου, ο τύπος της διάταξης των ηλεκτροδίων, η ύπαρξη νερού στη δοκιμαστική κυψέλη, η σχέση και συμπεριφορά του λαδιού με τον χρόνο και οι διαφοροποιήσεις στις ατμοσφαιρικές συνθήκες που επικράτησαν κατά τη διάρκεια του πειράματος. Πιο αναλυτικά η εργασία χωρίζεται σε κεφάλαια τα οποία είναι τα εξής: Στο 2ο κεφάλαιο γίνεται μια αναφορά στους μετασχηματιστές και στους τύπους μόνωσης που χρησιμοποιούνται στους διάφορους μετασχηματιστές σήμερα. Στο 3ο κεφάλαιο εξετάζεται στο σύστημα μόνωσης λαδιού - χαρτιού και στη συνέχεια παρουσιάζονται τα μονωτικά λάδια που έχουν χρησιμοποιηθεί στο παρελθόν μέχρι σήμερα. Στο 4ο κεφάλαιο γίνεται αναλυτική αναφορά στις ιδιότητες των μονωτικών λαδιών και συγκρίνονται οι ιδιότητες των ορυκτελαίων με αυτές των φυσικών εστέρων. Στο 5ο κεφάλαιο γίνεται αναφορά στους τρόπους διάσπασης των μονωτικών λαδιών. Στο 6ο κεφάλαιο εξετάζεται η γήρανση του συστήματος μόνωσης και οι παράγοντες που την επηρεάζουν. Στο 7ο κεφάλαιο παρουσιάζεται η εφαρμογή Retrofilling. Τέλος, στο 8ο κεφάλαιο παρουσιάζονται κάποιες διαγνωστικές τεχνικές για τον προσδιορισμό της κατάστασης της μόνωσης. Ακολουθεί το πειραματικό μέρος στα κεφάλαια 9, 10, 11 όπου αναλύονται τα χρησιμοποιηθέντα όργανα, παρουσιάζεται η διαδικασία των μετρήσεων βήμα προς βήμα και τελικά πραγματοποιείται η συγκέντρωση των αποτελεσμάτων σε πίνακες και περαιτέρω ανάλυσή τους με βάση τα απαραίτητα διαγράμματα για την εξαγωγή συμπερασμάτων. / The insulation of equipment and installation of high voltage is needed to maintain the potential difference between the high voltage conductive parts. Alongside the main destination, the insulation may have other roles, such as mechanical support of pipelines, heat exchange, etc. In this paper we dealt with electrotechnical fluids both theoretically and experimentally. In theory, we describe the role of insulating oils, uses, properties and factors affecting them. In experimental, we realize number of measurements to identify and draw conclusions using the device Baur Oil Tester DTA 822-129-1 electrical equipment high voltage laboratory. All measurements and choice of appropriate standard tests made by this device, each time taking the necessary measures to protect us and the installation of the laboratory. The insulating oil used is the natural ester Envirotemp ® FR3 ™, from the company COOPER Power Systems. Some of the factors considered are the size of the gap, the type of device electrodes, the presence of water in the test cell, the relationship and behavior of oil over time and variations in atmospheric conditions that prevailed during the experiment. More detailed work is divided into chapters which are: The second chapter is a reference to transformers and types of insulation used in the various transformers today. The third chapter discusses the system insulating oil - paper and then presented the insulating oils used in the past until today. The fourth section provides a detailed report on the properties of insulating oils and compares the properties of these oils with natural esters. The fifth chapter refers to the ways breakdown of insulating oil. The sixth chapter examines the aging of the insulation system and factors affecting it. The seventh chapter presents the implementation Retrofilling. Finally, the eighth chapter presents some diagnostic techniques for determining the state of the insulation. The experimental part in Chapters 9, 10, 11 analyzes the instruments used, shows the process of measuring step by step and finally is made the merger of the results in tables and further analysis based on the necessary diagrams to draw conclusions. The insulation of equipment and installation of high voltage is needed to maintain the potential difference between the high voltage conductive parts. Alongside the main destination, the insulation may have other roles, such as mechanical support of pipelines, heat exchange, etc. In this paper we dealt with electrotechnical fluids both theoretically and experimentally. In theory, we describe the role of insulating oils, uses, properties and factors affecting them. In experimental, we realize number of measurements to identify and draw conclusions using the device Baur Oil Tester DTA 822-129-1 electrical equipment high voltage laboratory. All measurements and choice of appropriate standard tests made by this device, each time taking the necessary measures to protect us and the installation of the laboratory. The insulating oil used is the natural ester Envirotemp ® FR3 ™, from the company COOPER Power Systems. Some of the factors considered are the size of the gap, the type of device electrodes, the presence of water in the test cell, the relationship and behavior of oil over time and variations in atmospheric conditions that prevailed during the experiment. More detailed work is divided into chapters which are: The second chapter is a reference to transformers and types of insulation used in the various transformers today. The third chapter discusses the system insulating oil - paper and then presented the insulating oils used in the past until today. The fourth section provides a detailed report on the properties of insulating oils and compares the properties of these oils with natural esters. The fifth chapter refers to the ways breakdown of insulating oil. The sixth chapter examines the aging of the insulation system and factors affecting it. The seventh chapter presents the implementation Retrofilling. Finally, the eighth chapter presents some diagnostic techniques for determining the state of the insulation. The experimental part in Chapters 9, 10, 11 analyzes the instruments used, shows the process of measuring step by step and finally is made the merger of the results in tables and further analysis based on the necessary diagrams to draw conclusions.

This research explores the use of insulated electrodes to determine electrical impedance distributions within soil cores. It is used to infer the effect of roots on soil moisture which, in turn, can provide knowledge relating to crop breeding programmes. These programmes are becoming increasingly important in order to address challenges posed by global population growth and climate change. Direct contact electrical impedance measurements in soil are frequently used but these are vulnerable to electrochemical effects and corrosion. Insulated electrodes are used in the present work to overcome these difficulties and a modified electrode model has been proposed. Measurements require the acquisition of spectroscopic complex impedance and extraction of the real impedance to infer soil moisture content. Calculated and simulated impedance, from the analytical solution and an FEM model respectively, were compared to measurements performed within a parallel-plate test cell containing saline solutions. The effects of moisture, compaction and temperature on soil impedance measurements have been explored. Finally, two growth trials using maize plants and control vessels were performed to create 2D images of impedance distributions, from which moisture placement was inferred. Results show that for saline electrolytes, the insulated electrode method was capable of estimating the impedance of tap water to within 10% of calibrated laboratory equipment. For soil based measurements, the variation of moisture content from 5-30% resulted in a 1000-fold decrease in impedance. The change was most significant in drier soils. For compaction based testing, at 5% moisture content soil impedance decreased by approximately 40%, compared to only 20% in the wettest samples. Temperature testing revealed an impedance change of approximately 2%/ °C, in agreement with earlier reports. Plant growth trials revealed increases in electrical impedance due to soil drying from an initial value of 1-2kΩ when the soil was wetted to field capacity, to as much as 60kΩ when dry. Only small changes were evident in the control vessels. It was also found that areas exposed to potential evaporation, such as at the surface closest to the plant stem, suffered significant losses in moisture content, reaching as high as 15-20kΩ. This research utilises a measurement technique which has not previously been used to measure soil impedance to infer moisture content. The research also found that the scaling of a thin layer within an FEM model can significantly reduce computational demands, while retaining accuracy, and allow more complex FEM simulations to be performed on a less powerful computer.