1,585 research outputs found

    Erfassung und Evaluierung von Teilentladungen in Leistungstransformatoren mit speziellen Sensoren und Diagnoseverfahren

    Get PDF
    Transformers are key elements of the power grid. Due to their importance and high initial cost, asset managers utilize monitoring and diagnostic tools to optimize their operation and extend their service life. The main objective of this thesis is to develop new methods in the field of monitoring and diagnosis of transformers in order to reduce maintenance costs and decrease the frequency of forced outages. For this purpose, two concepts are proposed. Small generator step-up transformers are essential in wind and photovoltaic parks. The first presented concept entails an online fault gas monitoring system for these transformers, specially hermetically-sealed transformers. The developed compact, maintenance-free and cost-effective monitoring system continuously tracks the level of the key leading indicators of transformer faults in the gas cushion. The second presented concept revolves around partial discharge (PD) assessment by the UHF measurement technique, which is based on capturing the electromagnetic (EM) waves emitted in case of PD in the insulation of a transformer. In this context, the complex EM system established when probes are introduced into the tank of a transformer and with PD as the excitation source is analyzed. Drawing on this foundation, a practical approach to the detection and classification of PD with the focus on the selection of the optimal frequency range for performing UHF measurements depending on the device under test is presented. The UHF measurement technique also offers the possibility of PD localization. Here, the determined arrival time (AT) of the captured signals is critical. A PD localization algorithm, based on a multi-data-set approach with a novel AT determination method, is proposed. The methods and algorithms proposed for the detection, classification and localization of PD are validated by means of practical experiments

    Precision spectroscopy of the 2S-6P transition in atomic deuterium

    Get PDF
    Die Quantenelektrodynamik (QED) bildet die Grundlage aller anderen Quantenfeldtheorien, auf denen das Standardmodell der Teilchenphysik aufgebaut ist. Derzeit ist klar, dass unser fundamentales Naturverständnis unvollständig ist, sodass erwartet wird, dass das Standardmodell um neue Teilchen oder Wechselwirkungen verändert oder erweitert werden muss. Eine Möglichkeit, diese Grenzen der Grundlagenphysik zu erforschen, ist die Durchführung von Präzisionsmessungen. Diese Arbeit untersucht die Präzisionslaserspektroskopie von Deuterium, wo die Übergangsenergien zwischen verschiedenen Energiezuständen des an den Kern gebundenen Elektrons mit Techniken wie ultrastabilen Lasern und dem Frequenzkamm genau gemessen werden können. Aufgrund der Einfachheit der wasserstoffähnlichen Atome können ihre Energieniveaus anhand der QED-Theorie für gebundene Zustände genau berechnet werden, und mit dem Experiment mit der relativen Genauigkeit in der Größenordnung von 101210^{-12} verglichen werden. Ein solcher Vergleich zwischen Theorie und Experiment ist mit der Bestimmung von Naturkonstanten verbunden, die als Parameter in die Theorie eingehen. Erst wenn mehr unabhängige Messungen als Parameter vorliegen, kann die Theorie überprüft werden. Der Vergleich zwischen Theorie und Laser-Spektroskopie im Deuterium betrifft die Ryd-berg-Konstante RR_\infty und den Deuteronen-Ladungsradius rdr_d. Dies erfordert mindestens zwei Messungen der verschiedenen Übergangsfrequenzen, um diese Konstanten zu bestimmen, und mehr Messungen, um die Theorie zu testen. Im Gegensatz zum Wasserstoff gibt es bei Deuterium nur wenige ausreichend genaue Messungen der Übergänge. In dieser Arbeit wird die erste Untersuchung des 2S-6P-Übergangs in Deuterium vorgestellt, die mit der bestehenden Frequenzmessung des 1S-2S-Übergangs kombiniert werden kann, um RR_\infty und rdr_d zu erhalten. Zusammen mit der Messung des 2S-2P-Übergangs von myonischem Deuterium stellt diese Bestimmung einen Theorietest dar. Ein solcher Vergleich ist wichtig, um die anhaltende Diskrepanz zwischen dem Ergebnis aus myonischem Deuterium und dem Durchschnitt früherer Daten aus elektronischem Deuterium, sowie die Spannungen zwischen den jüngsten Ergebnissen aus der Wasserstoffspektroskopie, zu beleuchten. Im Gegensatz zu Wasserstoff wird die Präzisionsspektroskopie des 2S-6P-Übergangs in Deuterium durch die gleichzeitige Anregung unaufgelöster Hyperfeinstruktur-Komponenten erschwert, was zur unaufgelösten Quanteninterferenz führen kann. Diese Arbeit untersucht die möglichen systematischen Effekte, die mit dieser Komplikation verbunden sind. Zusammen mit analytischen störungstheoretischen Modellen werden Supercomputersimulationen durchgeführt, um diese Effekte zu analysieren. Es wird gezeigt, dass die Quanteninterferenz für alle 2S-nnP-Übergänge in Deuterium stark unterdrückt wird, wodurch Präzisionsmessungen dieser Übergänge möglich werden. Darüber hinaus wird ein weiterer Effekt in Deuterium im Vergleich zu Wasserstoff untersucht, der sich aus der Lichtkraft ergibt, die auf die Atome in der stehenden Welle des Spektroskopielichts wirkt. Trotz zusätzlicher Zustandsvielfalt durch die gleichzeitige Anregung unaufgelöster Hyperfeinkomponenten wird gezeigt, dass diese sogenannte ``Lichtkraftverschiebung'' mit dem gut verstandenen Effekt im Wasserstoff vergleichbar ist. Die größte Herausforderung bei der Messung des 2S-6P-Ein-Photonen-Übergangs in Deuterium ist die Doppler-Verschiebung erster Ordnung. Ein großer Teil dieser Arbeit befasst sich daher mit dem verbesserten aktiven faserbasierten Retroreflektor (AFR), der eine Technik zur Unterdrückung dieser Verschiebung darstellt. Der zentrale Teil des AFR ist der Faserkollimator, der für die Erzeugung hochwertiger gegenläufiger Laserstrahlen erforderlich ist. Die Entwicklung und Charakterisierung eines solchen Kollimators für die nahe ultraviolette Wellenlänge des 2S-6P-Übergangs ist eine der wichtigsten Errungenschaften des verbesserten AFR. Die Ergebnisse dieser Arbeit können für andere Anwendungen von Interesse sein, bei denen eine hohe Strahlqualität oder wellenfront-zurückverfolgende Strahlen wichtig sind. Darüber hinaus werden die Einschränkungen der AFR untersucht, die sich aus polarisationserhaltenden Singlemode-Fasern ergeben. Neben anderen Verbesserungen wurde eine Polarisationsüberwachung der Spektroskopielaserstrahlen implementiert. Es werden verschiedene Charakterisierungsmessungen vorgestellt, um die Leistungsfähigkeit des verbesserten AFR zu demonstrieren. Schließlich wird in dieser Arbeit eine vorläufige Messung des 2S-6P-Übergangs in Deuterium vorgestellt. Für diese Messung wurde ein neuer Kryostat in die Apparatur eingebaut, der die Stabilität des Spektroskopiesignals durch reduzierte Temperaturschwankungen verbessert. Die Erzeugung des kryogenen Deuterium-Atomstrahls wurde in Abhängigkeit von der Düsentemperatur analysiert, was eine wichtige Studie für künftige Spektroskopiemessungen darstellt. Darüber hinaus wurden für die Präzisionsmessung verschiedene systematische Effekte untersucht, darunter die Fehlausrichtung des Atomstrahls und die elektrischen Streufelder. Es wird gezeigt, dass eine Präzisionsmessung des 2S-6P-Übergangs in Deuterium mit einer ähnlichen Unsicherheit wie in Wasserstoff machbar ist. Nach der vorläufigen Unsicherheitsabschätzung kann die 2S1/2_{1/2}-6P1/2_{1/2}-Übergangsfrequenz in Deuterium auf \SI{1.7}{kHz} bestimmt werden, was einer relativen Genauigkeit von 2.3×10122.3 \times 10^{-12} entspricht. Zusammen mit der 1S-2S-Messung kann dieses Ergebnis bereits die genauesten Bestimmungen des Deuteronenradius und der Rydberg-Konstante aus dem elektronischen Deuterium ermöglichen, sodass die Unsicherheiten für die Rydberg-Konstante und den Deuteronenradius δR5×105m1\delta R_\infty \simeq 5\times 10^{-5}\,\text{m}^{-1} bzw.~\delta r_d \simeq \SI{0.002}{fm} betragen. Dieses Ergebnis bildet die Grundlage für eine zukünftige Präzisionsmessung, bei der die 2S-6P-Übergangsfrequenz mit ähnlicher Genauigkeit wie bei Wasserstoff bestimmt werden soll, was δR2×105m1\delta R_\infty \simeq 2\times 10^{-5}\,\text{m}^{-1} und \delta r_d \simeq \SI{0.0007}{fm} entsprechen würde. Der Vergleich mit dem Ergebnis von myonischem Deuterium würde es dann erlauben, die QED-Theorie für gebundene Zustände auf dem Niveau von 9×10139 \times 10^{-13} zu testen.Quantum electrodynamics (QED) forms the basis for all other quantum field theories, upon which the Standard Model of particle physics is constructed. Currently, it is clear that our fundamental understanding of nature is incomplete, such that the Standard Model is expected to be modified or extended by new particles or interactions. One way to explore these frontiers of fundamental physics is to perform precision measurements. This thesis studies the precision laser spectroscopy of deuterium, where the transition energies between different energy states of the electron bound to the nucleus can be accurately measured with techniques such as ultra-stable lasers and the frequency comb. Due to the simplicity of hydrogen-like atoms, their energy levels can be precisely calculated from bound-state QED and confronted with the experiment with the relative accuracy on the order of 101210^{-12}. Such a comparison between theory and experiment is linked to the determination of fundamental constants, which enter the theory as parameters. Only if more indepedendent measurements are available than there are parameters, the theory can be tested. The comparison between theory and laser spectroscopy in deuterium concerns the Rydberg constant RR_\infty and the deuteron charge radius rdr_d. This requires at least two different transition frequency measurements to determine those constants, and more measurements to test the theory. Contrary to hydrogen, only few accurate enough transition frequency measurements are available in deuterium. This thesis presents the first study of the 2S-6P transition in deuterium, which can be combined with the existing 1S-2S transition frequency measurement to obtain RR_\infty and rdr_d. Together with the 2S-2P transition measurement from muonic deuterium, this determination provides a theory test. Such a comparison is important to shine light on the persisting discrepancy between the result from muonic deuterium and the average of previous data from electronic deuterium, as well as tensions between the recent results from hydrogen spectroscopy. In contrast to hydrogen, precision spectroscopy of the 2S-6P transition in deuterium is complicated by the simultaneous excitation of unresolved hyperfine components, possibly leading to unresolved quantum interference. This thesis studies the possible systematic effects associated with this complication. Along with analytical perturbative models, supercomputer simulations are performed to analyze these effects. It is shown, that quantum interference is strongly suppressed for all 2S-nnP transitions in deuterium, making precision measurements of these transitions possible. Furthermore, another effect is studied in deuterium compared to hydrogen, which arises from the light force acting on the atoms in the standing wave of the spectroscopy light. Despite additional state manifolds from the simultaneous excitation of unresolved hyperfine components, it is shown that this so-called ``light force shift'' is comparable to the well understood effect in hydrogen. The main challenge of measuring the one-photon 2S-6P transition in deuterium is the first-order Doppler shift. Therefore, a large part of this thesis contributes to the improved active fiber-based retroreflector (AFR), which is a technique to suppress this shift. The central part of the AFR is the fiber collimator, which is required to produce high-quality counter-propagating laser beams. Designing and characterizing such a collimator for the near ultra-violet wavelength of the 2S-6P transition is one of the main achievements of the improved AFR. The results of this work can be of interest to other applications where a high beam quality or wavefront-retracing beams are important. Furthermore, the limitations of the AFR arising from single-mode polarization-maintaining fibers are investigated. Along with other improvements, a polarization monitor of the spectroscopy laser beams has been implemented. Various characterization measurements are presented to demonstrate the performance of the improved AFR. Finally, this thesis presents a preliminary measurement of the 2S-6P transition in deuterium. For this measurement, a new cryostat has been installed in the apparatus, which improves the stability of the spectroscopy signal due to reduced temperature fluctuations. The cryogenic deuterium atomic beam generation has been analyzed in dependence on the nozzle temperature, which is an important study for future spectroscopy measurements. Furthermore, for the precision measurement different systematic effects have been investigated, including the atomic beam misalignment and the stray electric fields. It is demonstrated that a precision measurement of the 2S-6P transition in deuterium with a similar uncertainty than in hydrogen is feasible. According to the preliminary uncertainty budget, the 2S1/2_{1/2}-6P1/2_{1/2} transition frequency in deuterium can be determined to \SI{1.7}{kHz}, which corresponds to 2.3×10122.3 \times 10^{-12} relative accuracy. Together with the 1S-2S measurement, already this result can enable the most accurate determinations of the deuteron radius and the Rydberg constant from the electronic deuterium with the uncertainties on the Rydberg constant and the deuteron radius of δR5×105m1\delta R_\infty \simeq 5\times 10^{-5}\,\text{m}^{-1} and \delta r_d \simeq \SI{0.002}{fm}, respectively. This result sets the stage for a future precision measurement, where the 2S-6P transition frequency is expected to be determined with the similar accuracy as in hydrogen, which would correspond to δR2×105m1\delta R_\infty \simeq 2\times 10^{-5}\,\text{m}^{-1} and \delta r_d \simeq \SI{0.0007}{fm}. The comparison to the result from muonic deuterium would then allow to test bound-state QED at the level of 9×10139 \times 10^{-13}

    Advanced Sensing, Fault Diagnostics, and Structural Health Management

    Get PDF
    Advanced sensing, fault diagnosis, and structural health management are important parts of the maintenance strategy of modern industries. With the advancement of science and technology, modern structural and mechanical systems are becoming more and more complex. Due to the continuous nature of operation and utilization, modern systems are heavily susceptible to faults. Hence, the operational reliability and safety of the systems can be greatly enhanced by using the multifaced strategy of designing novel sensing technologies and advanced intelligent algorithms and constructing modern data acquisition systems and structural health monitoring techniques. As a result, this research domain has been receiving a significant amount of attention from researchers in recent years. Furthermore, the research findings have been successfully applied in a wide range of fields such as aerospace, manufacturing, transportation and processes

    Time for a Nappy Change: beliefs and attitudes towards modern cloth nappies.

    Get PDF
    The United Nations Environment Programme highlights how the use of disposable nappies has become unsustainable, yet the practice of using modern cloth nappies (MCN) is niche. This study uses mixed methods of survey, story completion and focus group methods to explore how behaviour beliefs and attitudes to behaviour contribute to families’ decision making regarding the nappy system they use for their children. 1588 responded to the survey; 38 completed story completion activity; 24 participated in groups. This study finds that beliefs about the performance as a nappy, environmental credentials, financial considerations, laundry, effort, and hygiene differ according to the level of personal experience of using MCN. While beliefs about the environmentalcredentials of MCN create powerful drivers for the intention to use MCN, other beliefs about the upfront costs, laundry and effort contribute a negative attitude to MCN overall if their support network of other MCN users is not established. Current MCN users found using cloth nappy retailer websites, nappy libraries, and social media groups, including pre-loved and-sell groups, to be beneficial in improving attitude to MCN. This study concludes that interventions that simultaneously reduce or remove perceived barriers such as upfront costs, financial risks and too much effort, paired with campaigns which increase the likelihood of finding support, are more likely, than individual interventions, to be effective in increasing the number of families using MCN.Further study is needed to investigate the potential of interventions which reduce the financial risks such as, easy to access hire kits, spread the cost of MCN and pre-natal and newborn public services such as midwives and health visitors being well informed and encouraging of the use of MCN.<br/

    Abstracts of the 1st GeoDays, 14th–17th March 2023, Helsinki, Finland

    Get PDF
    Non peer reviewe

    Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020)

    Get PDF
    The 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020) was held on 6–10 September 2020 in Beijing, China. The conference was organized by the Tsinghua University, China, and endorsed by the IEEE Dielectrics and Electrical Insulation Society. This conference has attracted a great deal of attention from researchers around the world in the field of high voltage engineering. The forum offered the opportunity to present the latest developments and different emerging challenges in high voltage engineering, including the topics of ultra-high voltage, smart grids, and insulating materials

    Changing Priorities. 3rd VIBRArch

    Full text link
    In order to warrant a good present and future for people around the planet and to safe the care of the planet itself, research in architecture has to release all its potential. Therefore, the aims of the 3rd Valencia International Biennial of Research in Architecture are: - To focus on the most relevant needs of humanity and the planet and what architectural research can do for solving them. - To assess the evolution of architectural research in traditionally matters of interest and the current state of these popular and widespread topics. - To deepen in the current state and findings of architectural research on subjects akin to post-capitalism and frequently related to equal opportunities and the universal right to personal development and happiness. - To showcase all kinds of research related to the new and holistic concept of sustainability and to climate emergency. - To place in the spotlight those ongoing works or available proposals developed by architectural researchers in order to combat the effects of the COVID-19 pandemic. - To underline the capacity of architectural research to develop resiliency and abilities to adapt itself to changing priorities. - To highlight architecture's multidisciplinarity as a melting pot of multiple approaches, points of view and expertise. - To open new perspectives for architectural research by promoting the development of multidisciplinary and inter-university networks and research groups. For all that, the 3rd Valencia International Biennial of Research in Architecture is open not only to architects, but also for any academic, practitioner, professional or student with a determination to develop research in architecture or neighboring fields.Cabrera Fausto, I. (2023). Changing Priorities. 3rd VIBRArch. Editorial Universitat Politècnica de València. https://doi.org/10.4995/VIBRArch2022.2022.1686
    corecore