Dissertations / Theses: 'High voltage insulating'

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Rux, Lorelynn Mary. "The physical phenomena associated with stator winding insulation condition as detected by the ramped direct high-voltage method." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-04042004-112949.

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Huldén, Pierre. "Conductivity measurement on thick insulating plaque samples." Thesis, KTH, Elektroteknisk teori och konstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150956.

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The conductivity is one of the main properties of HVDC cable insulation materials and needs to be evaluated carefully. Since measurement on cables is time consuming, often thin specimens and normal conductivity measurement cells are used to compare the materials. In this way however, the bulk effects will be less represented in the measurement and the results will be less representative. Instead, one needs to perform the measurements on thick plate samples and with higher voltage levels. This work focuses on the conductivity measurements on thick HVDC insulation plate samples subject to a high electric field and carefully controlled conditions. In the literature, there are many different methods of measuring the leakage current such as dielectric spectroscopy, PD, IV and PEA measurements. In this thesis a three electrode setup is used to measure the leakage current where the electrodes are placed inside the oven. This is to be able to control both temperature and high voltage under similar and different conditions where it is possible to change these two parameters during measurement. This was made by two Labview programs; one for creating a schedule and one control program which controls the equipment in the cell. The task was to make sure that the cell functioned by obtaining repeatable and reasonable measurements. The results that were obtained were reasonable and verified that the cell functioned. The executed measurements were performed in order to achieve a better understanding of error factors in the measurement system, ranging from preparing the sample to measuring the leakage current. The purpose with the cell is it to investigate the quality of the HVDC insulation by conductivity measurements on millimetre thick plate samples.
Den elektriska konduktiviteten är en av de viktigaste egenskaperna av HVDC kablars isolationsmaterial, XLPE, och den måste utvärderas noggrant. Mätning på fullskaliga kablar är tidskrävande och för att jämföra material används istället ofta tunna prover och normerade konduktivitetmätningsceller. En nackdel med denna metod är att bulkeffekterna blir mindre framträdande i mätningen och resultaten kommer att vara mindre representativa. Istället måste man utföra mätningen på tjockare prover och vid högre spänning. Detta examensarbete fokuserar på mätning av ledningsförmåga hos tjocka HVDC- isolationsprover under noggrant kontrollerade förhållanden och starka elektriska fält. I litteraturen finns det många olika metoder att mäta läckströmmar på, till exempel dielektrisk spektroskopi, PD, IV och PEA mätningar för att nämna några. I denna avhandling kommer ett tre-elektrod system att användas där en temperatursensor är monterad på ena elektroden. Systemet används för att både mäta läckströmmar och temperatur vid provet. Detta gör det möjligt att kontrollera temperatur och spänning oberoende av varandra vilket gjordes med hjälp av två Labview program. Det ena för att skapa ett schema och det andra användes som kontrollprogram för att styra utrustningen i cellen. Uppgiften var att kontrollera cellens funktion genom att erhålla rimliga repeterbara mätningar. Mätningarna gav rimliga resultat vilket indikerade att cellen fungerar tillfredställande. Syftet med mätningarna var att få en bättre förståelse för felfaktorer i mätsystemet som kan vara allt från att förbereda provet till att mäta läckström. Syftet med cellen är att undersöka isolationsegenskaperna på millimetertjocka pressade XLPE prover.

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Zavattoni, Laëtitia. "Conduction phenomena through gas and insulating solids in HVDC gas insulated substations, and consequences on electric field distribution." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT063/document.

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L'émergence des énergies renouvelables a entraîné le développement de nouvelles technologies pour la distribution de l'énergie sur de longues distances. Ces dernières sont basées sur le transport via de hautes tensions continues (HVDC) pour éviter les pertes capacitives. Ce réseau de distribution est interconnecté via des Postes Sous Enveloppes Métalliques (PSEM), dont l'isolation est composée de gaz sous pression (SF6) et d'isolants solides (résine époxy), qui doivent résister sous HVDC. Dans ces dispositifs, le champ électrique n'est plus déterminé par la permittivité relative des matériaux, mais par leurs résistivités et les phénomènes d'accumulation de charges. Dans le cas d'un isolant solide présentant une interface avec un gaz, des électrons ou des ions vont être susceptibles de se déplacer suivant les lignes de champ électrique et charger la surface de l'isolant solide. Le comportement des propriétés des isolants (solides et gazeux) constitue un enjeu majeur dans le développement de PSEM HVDC, notamment dans la compréhension des mécanismes d'accumulation et relaxation des charges.Dans ce travail de thèse, la caractérisation de l'isolant solide a d'abord été étudiée, basée sur des mesures de courants faibles bruits. Il est ainsi possible de mesurer le courant de fuite dans le volume et sur la surface des échantillons, dans une enceinte sous pression, à haut champ électrique et pour différentes températures. Ces mesures ont mis en évidence que les résistivités de volume et de surface sont fortement impactées par l'augmentation de la température et la teneur en eau des échantillons. Il a également été montré que la résistivité de surface a un comportement non-linéaire en fonction du champ électrique. Un modèle numérique a été développé pour simuler les résultats obtenus, et implémenter les propriétés de surface de l'isolant solide.Les propriétés isolantes du gaz ont également été étudiées pour différentes géométries de champ électrique, dans le but d'estimer la contribution du courant passant à travers le gaz, sur l'accumulation de charge en surface de l'isolant solide. Des courants non négligeables sont mesurés dans le gaz (~pA-nA). Pour déterminer les mécanismes responsables de la présence de tels courants, il a été caractérisé selon plusieurs paramètres (la rugosité de la surface de l'électrode, la nature du matériau, le champ électrique, la température et l'humidité relative). Cela a mis en évidence que les variations de courants dépendent du conditionnement du dispositif, et sont donc fortement influencés par l'humidité relative adsorbée sur les surfaces du dispositif (électrodes et cuves). En présence d'un système sec, de faibles courants sont mesurés (~pA), et augmentent en fonction de la température. A l'inverse, dans le cas d'un système humide, le courant diminue avec l'augmentation de la température. Ces résultats, combinés à l'influence de la rugosité de l'électrode, suggèrent fortement un mécanisme d'injection de charge à la surface de l'électrode, favorisé en présence d'eau adsorbée.Enfin, les résultats obtenus pour les deux isolants solides et gazeux sont utilisés pour élaborer un modèle numérique ayant une forme proche de celle de l'application industrielle, et permettent d'observer la modification de la distribution du champ électrique en présence de la concentration en eau et du gradient de température. Une estimation du courant circulant au travers des isolants est donc possible.En conclusion, ce travail donne les variations des résistivités de volume et de surface dans une résine époxy en fonction de la température et du champ électrique. Il met également en évidence la forte influence de l'humidité relative et de la température sur les mécanismes d'injection de charges qui contribuent au courant mesuré à travers le gaz. Cette caractérisation approfondie permet de développer une simulation qui prédit les variations de la distribution du champ électrique au sein d'un PSEM sous tension continue
The emergence of renewable energy leads to a development of new technologies for energy distribution across long distances. The latter will be based on High Voltage Direct Current (HVDC) to avoid capacitance losses. This network is interconnected using Gas Insulated Substation (GIS), which insulation is composed of pressurized gas (SF6) and solid insulators (epoxy resin), which have to withstand HVDC. The electric field is not anymore determined by permittivity of materials, but by resistivities and charge accumulation. In the case of an insulator with an interface with gas, electrons or ions will move across electric field lines and will charge the surface of the solid insulator. The behavior of insulator's properties (gas and solid) constitutes a major challenge for the development of HVDC GIS, to understand the charge relaxation/accumulation mechanisms.In this work, the characterization of solid insulator has first been investigated, based on a low-noise current measurement method. It is thus possible to measure the leakage current through samples and onto their surface, in a pressurized gas, at high electric field and for different temperatures. Those measurements permit to evidence that both volume and surface resistivities are strongly impacted by the increase of temperature and water concentration. It has also been shown that surface resistivity has a non-linear behavior with electric field. A numerical model was developed, to simulate experimental results, showing that the surface properties of the insulator can be implemented.Furthermore, the insulating properties of the gas were also investigated through different electric field geometry (coaxial and uniform), in order to estimate the contribution of current through gas on the charge accumulated on solid insulators. It has been found that a non-negligible current passes through the gas (~pA to nA). To determine the mechanisms responsible for such currents, the latter has been characterized depending on several parameters (electrode surface roughness, material nature, electric field, temperature and relative humidity). It revealed that the variations of currents are strongly impacted by the conditioning of the device and thus by the relative humidity adsorbed on electrodes and enclosure surfaces. In presence of a dry system (dry gas and device) low current were measured (~pA), which increases with temperature. On the contrary, in case of a “wet” system (humid gas and device) the current decreases with increasing temperature. Those results combined with the influence of the electrode roughness, strongly suggest a mechanism of charge injection at the electrode surface, enhanced by water adsorption.Finally, the results obtained for both solid and gaseous insulations are used to develop a numerical model with a shape close to the industrial application, and observe the modification of electric field distribution in presence of water concentration and temperature gradient. An estimation of current flowing through the insulator and gas is thus possible in case of uniform and gradient temperature.In conclusion, this work gives the variations of both volume and surface resistivities in an epoxy resin with temperature and electric field. It also evidences the major influence of relative humidity and temperature on charge injection mechanisms which contribute to the current measured through gas. The extensive characterization performed, enables to develop a simulation which predicts the variations of electric field distribution within an HVDC GIS

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Yahyaoui, Hanen. "Matériaux isolants pour appareillages haute tension dans le domaine du courant continu : comportement et vieillissement." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS267.

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Les projets de mise en place dans les prochaines décennies de « super réseaux intelligents », qui prévoient la construction de centrales de production à des milliers de kms des centres de consommation, nécessite le développement à large échelle du transport de très fortes puissances par câbles à courant continu. Les principaux verrous à ce développement se situent au niveau du câble et des appareillages adéquats, qui doivent être conçus sur des critères spécifiques et comporter des matériaux isolants ayant des propriétés particulières. Outre la variation de la résistivité qui dépend fortement du champ électrique et de la température, il est établi que des charges sont injectées dans la matière isolante, donnant lieu à une charge d'espace modifiant la répartition du champ électrique. Dans le cas d'un renforcement du champ électrique, la présence de charges d'espace peut conduire à une accélération du vieillissement électrique et, par suite, à un phénomène auto-accélérant pour la rupture diélectrique. Le comportement de ces matériaux sous fortes contraintes continues et en particulier leur vieillissement reste aujourd'hui mal connu.Ce travail de thèse concerne ainsi l'étude du comportement diélectrique de résines époxydes chargées d'alumine utilisées comme supports isolants dans les disjoncteurs à isolation gazeuse en vue d'évaluer leur aptitude à être utilisées dans des appareillages de coupure haute tension continue. Les différentes propriétés diélectriques de ce matériau à l'état initial (facteur de pertes, résistivité volumique, seuils et coefficients de non linéarité, résistivité surfacique, rigidité diélectrique, évolution des charges d'espace) sont déterminées et étudiées sous contrainte électrique continue et à différentes températures.Afin de mieux évaluer l'effet à long terme de la charge d'espace sur le matériau et d'en tirer des informations approfondies pour la conception des futurs composants pour la haute tension à courant continu, une étude de vieillissement accéléré sous contraintes électriques (champs continus) et thermiques (différentes températures) est réalisée. En plus de la charge d'espace, les autres paramètres analysés (permittivité, pertes diélectriques) constituent également des marqueurs potentiels du vieillissement du matériau. L'analyse de l'évolution de ces marqueurs constitue une phase nécessaire dans la compréhension du comportement du matériau pour une utilisation en haute tension à courant continu
The development of high voltage dc equipment requires design according to specific criteria and including materials with appropriate properties. Indeed, while in ac the dielectric behaviour is mainly determined by permittivity, which varies little for the used materials with field and temperature at power frequency, the dc behavior is determined by highly non-linear volume and surface conductivity-related phenomena. Thus, it is well known that, in dc conditions, electric charge is injected and trapped in the bulk and on the surface, affecting the distribution of the electric field. Space charge accumulation is able to increase significantly the values of the field, thus accelerating ageing and increasing the risk of breakdown. The electrode nature, the field and temperature dependence of the electrical conductivity of the insulating material are key factors involved in the high dc field phenomena.Epoxy resins form an important category of polymeric insulating materials used in a wide range of electric power installations and equipment. In particular, they have been used especially as insulating supports for ac Gas Insulated Switchgear (GIS), because of their electrical and mechanical properties. However, the behaviour of these materials under high dc stress is less known and needs thorough investigation in view of dc applications.The purpose of this thesis is to investigate dielectric behavior of epoxy resins in order to assess their suitability for use in high DC voltage switchgear and define actions and criteria support for the design of such devices.We start by presenting the most important chemical thermal and dielectric properties of polymers as well as the various properties of the epoxy resin.Dielectric properties of the material at initial state with continuous temperature and electrical stress (loss factor, volume resistivity, thresholds and nonlinearity coefficients, surface resistivity, breakdown, evolution of space charge) are determined and investigated under dc fields at different temperatures

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Silva, Igor. "Propriétés des matériaux isolants pour application dans les appareillages moyenne tension à tension continue." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALT043.

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Les récentes avancées dans la technologie du courant continu, du côté du transport à haute tension et de la consommation à basse tension, ont propulsé le courant continu de moyenne tension (MVDC) au premier plan. Cette thèse explore les propriétés isolantes en courant continu de deux matériaux couramment utilisés dans l'équipement de distribution : de l'époxy chargé en micro-silice et le silicone elastomère.Dans une configuration monocouche, chaque matériau a fait l'objet d'une enquête approfondie, mettant l'accent sur les caractéristiques de sorption d'eau et la conduction électrique. Des mesures de courant ont été effectuées pour analyser la conduction dans divers niveaux de champs, à différentes températures et conditions d'absorption d'eau. De plus, la méthode Laser Pressure Pulse (LIPP) a été utilisée pour des mesures de charge d'espace en tant que technique complémentaire. L'étude s'est étendue à une configuration bicouche, combinant les deux matériaux, nous permettant ainsi de confirmer un modèle prédisant les propriétés du multicouche et sa distribution de champs en fonction des valeurs des monocouches.La conduction en courant continu dans l'époxy a montré une forte dépendance à l'absorption d'eau, l'humidité influençant la non-linéarité et modifiant le mécanisme de conduction. À l'inverse, le silicone a démontré une conduction limitée par l'électrode, avec des variations de courant liées à la sorption d'eau par le biais d'un mécanisme limité par saturation. Dans une configuration bicouche hypothétique, où l'époxy représente un manchon et le silicone sert de terminaison de câble, le champ est censé se concentrer dans l'époxy dans des environnements secs, passant au silicone à mesure que l'humidité augmente. La thèse se conclut par des discussions sur les stratégies de sélection des matériaux et la conception de configurations multicouches
Recent advancements in direct-current technology from the high-voltage transport and low-voltage consumption have brought medium-voltage DC (MVDC) to the forefront. This thesis delves into the insulating DC properties of two commonly used materials in distribution equipment: epoxy filled with silica and silicone rubber.In a monolayer configuration, each material underwent extensive investigation, focusing on water sorption characteristics and electrical conduction. Current measurements were conducted to analyze conduction under various fields, temperatures, and water uptake conditions. Additionally, the Laser Pressure Pulse (LIPP) method was employed for space charge measurements as a complementary technique. The study extended to a bilayer configuration, combining both materials, with insights from monolayer experiments informing the properties of the bilayer and predicting field distribution.The DC conduction in epoxy exhibited high dependence on water absorption, with moisture influencing non-linearity and altering the conduction mechanism. Conversely, silicone demonstrated electrode-limited conduction, with current variations tied to water sorption through a saturation-limited mechanism. In a hypothetical bilayer configuration, where epoxy represents a type-C bushing and silicone serves as the cable termination, the field is expected to concentrate in the epoxy in dry environments, shifting to silicone as humidity increases. The thesis concludes with discussions on material selection strategies and the design of multi-layer configurations

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Freye, Claudius [Verfasser], Frank [Akademischer Betreuer] Jenau, and Thomas [Gutachter] Leibfried. "Methoden und Aspekte zur Leitfähigkeitsanalyse von Isolationsmaterialien der Kabeltechnologie und zur Isolationskoordination für Systeme der Hochspannungsgleichstromübertragung (HGÜ) : Methods and aspects for conductivity analysis of insulating materials in cable technology and for insulation coordination in high-voltage direct current transmission (HVDC) systems / Claudius Freye ; Gutachter: Thomas Leibfried ; Betreuer: Frank Jenau." Dortmund : Universitätsbibliothek Dortmund, 2020. http://d-nb.info/1214887627/34.

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Bialek, Thomas Owen. "Evaluation and modeling of high-voltage cable insulation using a high-voltage impulse." Diss., Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/content/templates/?a=72.

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Luo, Jing. "Novel insulation techniques for high voltage pulse transformers." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/13327.

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This thesis describes a research investigation into novel designs of high voltage pulse transformers using magnetic insulation, which is the only practicable form of insulation for much of the equipment presently used in ultrahigh voltage pulsed-power work, including transmission lines and plasma opening switches. Although its use in transformers would bring important advantages in both size and weight reductions, a number of seemingly insurmountable problems have however so far prevented this. Two novel arrangements are presented in this thesis: one of these is a 500 kV transformer with self-magnetic insulation, and the other one is a 1 MV 'Tesla' transformer with external magnetic insulation. It is shown that both of these overcome the problems inherent in earlier designs and also offer considerable scope for further development in a number of important areas. It is believed that they represent the first working examples of magnetically-insulated transformers anywhere in the world. Modelling considerations of the transformers developed include both theoretical models and predicted characteristics. The filamentary technique used to describe mathematically the arrangements being investigated involves decomposition of the main conducting components into filamentary elements. The resulting equivalent electrical network includes all the mutual interactions that exist between the different filamentary elements, takes magnetic diffusion fully into account and enables the resistances and self and mutual inductances that are effective under fast transient conditions to be calculated. Theoretical results provided by the resulting mathematical models have been successfully validated by comparison with reliable experimental data. Much of the work detailed in the thesis has already been presented in high quality academic journals and at prestigious international conferences, and a solid theoretical and experimental basis has been laid down for future development and new progress into pulsed power system research.

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Hare, Richard W. "Modelling space charge in solid dielectrics." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482030.

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Wallström, Stina. "Biofilms on silicone rubber for outdoor high voltage insulation." Doctoral thesis, KTH, Fiber- och polymerteknik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171.

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Silicone rubber high voltage insulators are sometimes colonised by microorganisms which form a biofilm on the surface of the infected unit. In this work insulators exposed to the outdoor environment in Sweden, Sri Lanka and Tanzania respectively have been studied. The biofilms colonising the insulators were shown to be of roughly the same composition regardless of their origin. Algae in association with bacteria dominated the biofilms and provided nutrition to mold growth. The isolated microorganisms were further used to study the effect of a biofilm on different silicone rubber materials. New tools for diagnosing biological growth on polymeric materials were developed and used to analyse the silicone rubber samples. No evidence of biodegradation of the polydimethylsiloxane (PDMS) molecule has been found in this work. However, this does not mean that PDMS rubbers used in high voltage insulators can be called bioresistant. Silicone insulating materials always contain additives and these may promote or hinder growth. For this reason, an extensive test program was developed, in order to evaluate the effect of different additives on the degree of biological growth. The program spanned from fast and easy methods, useful for screening large amount of samples, to the construction of specially designed microenvironment chambers in which mixed biofilms, similar to those formed on the surface of silicone rubber insulators in the field, were successfully grown. The test program showed that the flame retardant zinc borate protected the materials, whereas alumina trihydrate (ATH) did not hinder biological growth. On the contrary, environmental scanning microscopy (ESEM) in combination with X-ray energy dispersive spectroscopy (EDS) showed that the surface roughening caused by the addition of ATH to the silicone rubber matrix made the materials more difficult to clean. Furthermore when the hydrophobic surface of a silicone rubber insulator is covered by a hydrophilic biofilm this leads to a reduction of the surface hydrophobicity of the material. This may alter the electrical properties of the insulator. It is therefore important to develop methods to identify biofouled units. In this work, laser-induced fluorescence (LIF) spectroscopy was explored as a tool for the detection of biofilms on silicone rubbers. The experiments revealed that weak traces of algae or fungal growth, even those not visible to the naked eye, could be detected by this technique. In addition, it was shown that photography and subsequent digital image analysis could be utilised to estimate the area covered by biofilm growth. The results obtained indicate that LIF spectroscopy in combination with image analysis could be used for field diagnostics of biological growth on insulators in service.

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Washabaugh, Andrew Patrick. "Electrokinetic pumping of semi-insulating liquids by traveling wave high voltages." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14509.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1989.
Includes bibliographical references (leaves 182-184).
by Andrew Patrick Washabaugh.
M.S.

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Wallström, Stina. "Biofilms on silicone rubber for materials outdoor high voltage insulation /." Stockholm : Univ, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171.

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Goss, Ben. "Degradation and life time prediction of high voltage insulation materials." Thesis, Queensland University of Technology, 2001.

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Okubo, H., M. Hikita, H. Goshima, H. Sakakibara, and N. Hayakawa. "High voltage insulation performance of cryogenic liquids for superconducting power apparatus." IEEE, 1996. http://hdl.handle.net/2237/6879.

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Cargill, Steven M. "Corona screen effectiveness in large machines under high voltage, high frequency transient conditions." Thesis, Robert Gordon University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298316.

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Saeishirazi, Mohammadmahdi [Verfasser]. "Influence of Nanofillers on High Voltage Polymeric Solid Insulation Systems / Mohammadmahdi Saeishirazi." München : Verlag Dr. Hut, 2014. http://d-nb.info/1060587580/34.

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Whitfield, Thomas Britain. "An analysis of copper transport in the insulation of high voltage transformers." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843581/.

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Examination of the paper insulation and copper stress braiding during stripdown of a number of Current Transformers (FMK type 400kV) has revealed the presence of dark deposits. Copper foils are often interspersed within layers of paper insulation and mineral oil found in transformer windings. The dark deposits were often found in association with these foils, affecting several layers of paper in addition to the layer in contact with the copper foil. This thesis describes the research undertaken to identify these deposits and establish a mechanism for the transportation through the paper layers. Preliminary investigation using scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray analysis (EDX) has shown these dark deposits to be copper based. X-ray photoelectron spectroscopy was used to show that the transport of the copper deposit through the paper insulation was working under the influence of a diffusion controlled process, related to Fick's law. Laboratory studies in support of work designed to eliminate the problem have shown that corrosion of copper occurs in mineral oils containing a trace of oxygen. This corrosion is non protective in character and leads to migration of copper into adjacent layers of paper. It has been shown that the transport of copper through several layers of paper can be measured by XPS and that the concentration from one paper winding to the next declines in accord with Fick's law for non-steady state diffusion. Measurements of surface concentrations by XPS correlate well with measurements made with atomic absorption spectroscopy on solutions of extracts of the contaminated paper. The laboratory measurements have allowed determination of the diffusion coefficients and activation energy for the transport process and thus give a basis for interpretation of the diffusion profiles found in the transformer in terms of time and temperature of operation. The diffusion process is temperature dependant. The results have been used to produce long term prediction curves.

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Wang, Pei. "Computer based on-line diagnostics of insulation quality of high voltage apparatus." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0020/MQ53240.pdf.

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Cariou-Saintemarie, Nathalie. "Initiation of electrical degradation in high voltage polymeric cable insulation : electroluminescence detection." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342808.

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Zhao, Shishuo. "High Frequency Isolated Power Conversion from Medium Voltage AC to Low Voltage DC." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74969.

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Modern data center power architecture developing trend is analyzed, efficiency improvement method is also discussed. Literature survey of high frequency isolated power conversion system which is also called solid state transformer is given including application, topology, device and magnetic transformer. Then developing trend of this research area is clearly shown following by research target. State of art wide band gap device including silicon carbide (SiC) and gallium nitride (GaN) devices are characterized and compared, final selection is made based on comparison result. Mostly used high frequency high power DC/DC converter topology dual active bridge (DAB) is introduced and compared with novel CLLC resonant converter in terms of switching loss and conduction loss point of view. CLLC holds ZVS capability over all load range and smaller turn off current value. This is beneficial for high frequency operation and taken as our candidate. Device loss breakdown of CLLC converter is also given in the end. Medium voltage high frequency transformer is the key element in terms of insulation safety, power density and efficiency. Firstly, two mostly used transformer structures are compared. Then transformer insulation requirement is referred for 4160 V application according to IEEE standard. Solid insulation material are also compared and selected. Material thickness and insulation distance are also determined. Insulation capability is preliminary verified in FEA electric field simulation. Thirdly two transformer magnetic loss model are introduced including core loss model and litz wire winding loss model. Transformer turn number is determined based on core loss and winding loss trade-off. Different core loss density and working frequency impact is carefully analyzed. Different materials show their best performance among different frequency range. Transformer prototype is developed following designed parameter. We test the developed 15 kW 500 kHz transformer under 4160 V dry type transformer IEEE Std. C57.12.01 standard, including basic lightning test, applied voltage test, partial discharge test. 500 kHz 15 kW CLLC converter gate drive is our design challenge in terms of symmetry propagation delay, cross talk phenomenon elimination and shoot through protection. Gate drive IC is carefully selected to achieve symmetrical propagation delay and high common mode dv/dt immunity. Zero turn off resistor is achieved with minimized gate loop inductance to prevent cross talk phenomenon. Desaturation protection is also employed to provide shoot through protection. Finally 15 kW 500 kHz CLLC resonant converter is developed based on 4160V 500 kHz transformer and tested up to full power level with 98% peak efficiency.
Master of Science

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Ariffin, Azrul Mohd. "The measurement and modelling of electroluminescence in high voltage polymeric cable insulation materials." Thesis, University of Southampton, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494683.

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Since space charge plays a significant role in long-term electrical degradation of polymeric insulation in high voltage cables, there is growing interest in the measurement of the energy dissipation of mobile and trapped charges in the dielectric molecules. The dissipation process is associated with the emission of visible photons, a process known as electroluminescence (EL) and can be used, potentially, as an indicator for the inhibition of electrical ageing of insulation. This thesis is based on an investigation into the occurrence of EL in dielectric materials as a result of applying high ac stresses. The phenomenon has been observed and analyzed for different types of thin polymeric films using a charge coupled device (CCD) detection system. This unique experimental setup enables a range of measurements to be performed including the imaging of EL, its temporal behaviour, spectral analysis and phase-resolved measurements using the same detector. The effects of several factors such as the types of material under study and local gas environment have been assessed based on the results obtained. Previously, different research groups have monitored the occurrence of EL under ac conditions by applying a sinusoidal electric field across the polymer but in this project, the emission is also examined under the influence of triangular and square voltage waveforms, together with their asymmetrical counterparts. In addition to this, a dynamic bipolar charge recombination model has been developed in order to simulate studies of EL under an alternating field. By comparing experimental results with the stimulation, the theories relating to the processes responsible for the occurrence of EL have been evaluated and a good agreement was found between the simulation and experimental results.

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Montasser, Yuseph. "Design and Development of a Power Modulator for Insulation Testing." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2895.

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Variable speed drives allow for more precise speed control of induction motors, are of high power factor, and offer fast response characteristics, compared to older technologies, such as motor-generator sets and eddy current clutches. However, due to the high switching frequencies as well as the high dV/dt in the output increased dielectric stresses are produced in the insulation system of the motor they supply. Due to the use of these solid state drives there have been concerns of premature failure in large, medium and high voltage, motors. To fully understand and deal with these concerns requires studying the degradation mechanisms, in the insulation system, caused by these drives; which, on an actual motor is both extremely costly as well as impractical. Therefore, coil samples which accurately represent the construction of the actual insulation system, must be aged and studied instead. In addition, to ideally replicate the aging process, the same waveform that the motor is subjected to must be applied to these samples. As a result of this requirement, a low power, two-level, high voltage PWM inverter has been built to replicate the most important characteristics of the output waveform of a variable speed drive. This power modulator allows for testing the insulation systems considering a real PWM waveform in which both the fast pulses and the fundamental low frequency are included. The results of these tests show that the effects of PWM waveforms cannot be entirely replicated by a unipolar pulse generator.

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Mesgarpour, Tousi Maryam. "Electric Field Grading and Electrical Insulation Design for High Voltage, High Power Density Wide Bandgap Power Modules." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/100621.

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The trend towards more and all-electric apparatuses and more electrification will lead to higher electrical demand. Increases in electrical power demand can be provided by either higher currents or higher voltages. Due to "weight" and "voltage" drop, a raise in the current is not preferred; so, "higher voltages" are being considered. Another trend is to reduce the size and weight of apparatuses. Combined, these two trends result in the high voltage, high power density concept. It is expected that by 2030, 80% of all electric power will flow through "power electronics systems". In regards to the high voltage, high power density concept described above, "wide bandgap (WBG) power modules" made from materials such as "SiC and GaN (and, soon, Ga2O3 and diamond)", which can endure "higher voltages" and "currents" rather than "Si-based modules", are considered to be the most promising solution to reducing the size and weight of "power conversion systems". In addition to the trend towards higher "blocking voltage", volume reduction has been targeted for WBG devices. The blocking voltage is the breakdown voltage capability of the device, and volume reduction translates into power density increase. This leads to extremely high electric field stress, E, of extremely nonuniform type within the module, leading to a higher possibility of "partial discharge (PD)" and, in turn, insulation degradation and, eventually, breakdown of the module. Unless the discussed high E issue is satisfactorily addressed and solved, realizing next-generation high power density WBG power modules that can properly operate will not be possible. Contributions and innovations of this Ph.D. work are as follows. i) Novel electric field grading techniques including (a) various geometrical techniques, (b) applying "nonlinear field-dependent conductivity (FDC) materials" to high E regions, and (c) combination of (a) and (b), are developed; ii) A criterion for the electric stress intensity based upon accurate dimensions of a power device package and its "PD measurement" is presented; iii) Guidelines for the electrical insulation design of next-generation high voltage (up to 30 kV), high power density "WBG power modules" as both the "one-minute insulation" and PD tests according to the standard IEC 61287-1 are introduced; iv) Influence of temperature up to 250°C and frequency up to 1 MHz on E distribution and electric field grading methods mentioned in i) is studied; and v) A coupled thermal and electrical (electrothermal) model is developed to obtain thermal distribution within the module precisely. All models and simulations are developed and carried out in COMSOL Multiphysics.
Doctor of Philosophy
In power engineering, power conversion term means converting electric energy from one form to another such as converting between AC and DC, changing the magnitude or frequency of AC or DC voltage or current, or some combination of these. The main components of a power electronic conversion system are power semiconductor devices acted as switches. A power module provides the physical containment and package for several power semiconductor devices. There is a trend towards the manufacturing of electrification apparatuses with higher power density, which means handling higher power per unit volume, leading to less weight and size of apparatuses for a given power. This is the case for power modules as well. Conventional "silicon (Si)-based semiconductor technology" cannot handle the power levels and switching frequencies required by "next-generation" utility applications. In this regard, "wide bandgap (WBG) semiconductor materials", such as "silicon carbide (SiC)"," gallium nitride (GaN)", and, soon, "gallium oxide" and "diamond" are capable of higher switching frequencies and higher voltages, while providing for lower switching losses, better thermal conductivities, and the ability to withstand higher operating temperatures. Regarding the high power density concept mentioned above, the challenge here, now and in the future, is to design compact WBG-based modules. To this end, the extremely nonuniform high electric field stress within the power module caused by the aforementioned trend and emerging WBG semiconductor switches should be graded and mitigated to prevent partial discharges that can eventually lead to breakdown of the module. In this Ph.D. work, new electric field grading methods including various geometrical techniques combined with applying nonlinear field-dependent conductivity (FDC) materials to high field regions are introduced and developed through simulation results obtained from the models developed in this thesis.

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Nikjoo, Roya. "Dielectric Response and Partial Discharge Diagnostics of Insulation Systems by Utilizing High Voltage Impulses." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187632.

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In this thesis, power system transients are considered as an opportunity for development of on-line diagnostics of power components and specifically the insulation systems of power transformers and bushings. A new technique for on-line dielectric response measurement of power transformer bushings is proposed which utilizes natural transients in the power system, such as lightning and switching surges, as stimuli. Laboratory investigations are done on implementation of the proposed technique. Measurement considerations, data acquisition and processing involved in achievement of reasonable accuracy in the Dielectric Response (DR) are presented. Capability of the technique in tracking of the degradation signatures such as moisture content in the insulation has been evaluated and it has shown a good level of accuracy by being compared to the Frequency Domain Spectroscopy (FDS). The proposed technique is tested on the service-aged 150 kV bushings and feasibility of the technique for monitoring of dielectric properties of power transformer bushings has been assessed; the results are promising for the technique to be used in the real application. Partial Discharges (PD) behavior under transients has been also studied for different materials in this project. PD behavior of different defects, at different insulation condition, responding to the overvoltage transients in form of superimposed impulses on ac voltages was investigated and it was perceived how their distinctive response and the interpretation of that, can be useful for their identification. Besides the conventional materials, surface ac PD properties of modified paper with silica and zinc oxide nanoparticles under the superimposed impulses have been assessed in this project. Proper type and optimum concentration level of nanoparticles in the paper are the factors that lead to the improvement of PD behavior in the modified paper under overvoltage transients.

QC 20160525

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25

Blackmore, Paul David. "Degradation of polymeric outdoor high voltage insulation : surface discharge phenomena and condition assessment techniques." Thesis, Queensland University of Technology, 1997.

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Benwell, Andrew L. "Flashover prevention on polystyrene high voltage insulators in a vacuum." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5018.

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Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 18, 2008) Includes bibliographical references.

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Tran, Van Top. "Étude de la génération des streamers dans l'huile minérale sous tension impulsionnelle et alternative." Grenoble INPG, 1999. http://www.theses.fr/1999INPG0024.

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L'objectif de cette these est d'etudier la generation des streamers dans l'huile minerale sous tension impulsionnelle et tension alternative avec des conditions de champ largement variees en presence de certaines pollutions (particules et eau). Ce travail apporte une meilleure comprehension de la generation des phenomenes precurseurs du claquage. Les resultats obtenus mettent en evidence l'influence importante de la geometrie et des impuretes (particules, eau) sur la generation des streamers. Un effet remarquable de diminution du champ de generation avec l'augmentation du rayon de courbure de l'electrode est observe. Cette diminution est l'origine de l'effet de surface generalement observe sous creneaux de tension et sous tension alternative dans l'huile tres bien filtree. Une degradation supplementaire existe lorsque l'huile est polluee et soumise a la tension alternative. L'etude realisee en geometrie semi-uniforme (plan-plan avec une electrode d'amorcage) permet de simuler les conditions de generation et de propagation des streamers provoques par des particules ou des asperites de la surface en geometrie uniforme.

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Bandaru, Sreekanth. "Effect of high frequency pulse voltages and high temperature on the lifetime characteristics of magnet wires." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-05132004-135217.

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Gavrilenko, Veronika. "Characterization of winding insulation of electrical machines fed by voltage waves with high dV/dt." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST027.

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L’isolation des bobinages des moteurs alimentés par des convertisseurs statiques basés sur la modulation de largeur d'impulsion est soumise à des contraintes électriques provenant de la forme d'onde de la tension d'alimentation. Les phénomènes de nuisances électromagnétiques sur l’ensemble de la chaîne de conversion, les ondes réfléchies dans le câble d’alimentation, ainsi que la non adaptation des impédances du câble et de l’enroulement de la machine peuvent conduire à l’apparition de surtensions aux bornes de la machine suffisamment élevées pour dépasser la tension d’apparition des décharges partielles. Il en résulte une dégradation de l’isolation entre les spires qui, à terme, peut engendrer la défaillance de la machine. La mise en œuvre de composants à semi-conducteurs grand gap, tel que le Carbure de Silicium, permet la réalisation de convertisseurs de forte densité de puissance pour les systèmes d’entraînement à vitesse variable des machines électriques. Les vitesses et les fréquence de commutation élevées de ces composants conduisent à des contraintes électriques en dV/dt plus sévères sur l'isolation des enroulements des moteurs alimentés par de tels convertisseurs. L’étude expérimentale et les simulations numériques réalisées dans le cadre de cette thèse se concentrent essentiellement sur les effets des ondes de tension à forts dV/dt et de la fréquence de commutation élevée sur la robustesse de l’isolation du bobinage des machines électriques alimentées par des onduleurs. Par conséquent, les travaux touchent un certain nombre de questions liées à l’entraînement à vitesse variable, à l’électronique de puissance, aux machines électriques, aux matériaux diélectriques et aux décharges partielles
The insulation of electrical machines driven by power converters with pulse width modulation are subjected to repetitive surges due to fast changing voltage pulses and reflection phenomena in supply cable, as well as non-uniform voltage distribution in the stator winding. The overvoltage at motor terminals may lead to partial discharge inception accelerating winding insulation degradation and causing its premature failure. The implementation of wide bandgap power semiconductors as Silicon Carbide allows to create converters with high power density for variable frequency drive applications. The fast and high frequency switching of electronic devices based on wide bandgap semiconductors increase electrical stresses caused by steep voltage changing rates in controlled electrical machine. It may increase a risk of partial discharges and accelerate insulation aging and destruction. The experimental investigation and numerical simulation study performed in this work is essentially focused on the effects of impulse voltage with high dV/dt and high switching frequency on winding insulation robustness of inverter-fed electrical machines. Therefore, the work covers a number of issues related to electric drives, power electronics, electrical machines, dielectric materials and partial discharges

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Desmars, Loriane. "Etude des propriétés électriques et thermiques de matériaux composites à matrice époxy-anhydride pour l'isolation haute tension." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI021.

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L’avènement des énergies renouvelables, notamment offshore, et la nécessité de transporter l’électricité sur des distances toujours plus grandes tout en réduisant les pertes en ligne requièrent la mise en place d’un nouveau réseau électrique plus performant, le supergrid. L’amélioration des sous-stations ultra haute tension en courant alternatif (UHVAC) de type poste sous enveloppe métallique (PSEM), i.e. la réduction de leur empreinte au sol ou leur montée en tension, s’inscrit parmi les défis engendrés par le développement du supergrid. L’amélioration de la tenue aux contraintes électrothermiques des isolants solides employés dans les PSEM a été identifiée comme le principal verrou technologique pour le perfectionnement de ces appareillages, déjà pleinement maîtrisés en HVAC. Les travaux présentés dans ce manuscrit ont été motivés par la nécessité de développer un matériau isolant électrique plus performant que les matériaux existant actuellement sur le marché. L’un des matériaux couramment employés pour la fabrication d’isolants solides pour PSEM, une matrice époxy-anhydride chargée d’alumine micrométrique, a servi de référence commerciale à notre étude. Suite à une étude bibliographique, nous avons choisi de conserver la matrice époxy du système commercial de référence et de jouer sur les charges inorganiques employées pour optimiser les propriétés du matériau isolant. Les travaux présentés mettent en évidence l’influence de la nature des charges inorganiques (alumine ou nitrure de bore hexagonal), de leur facteur de forme (quasi sphérique ou lamellaire) et de leur fraction volumique sur la conductivité thermique, le coefficient d’expansion thermique, les propriétés mécaniques dynamiques, les propriétés diélectriques, la conductivité électrique à haute tension (DC) et la rigidité diélectrique (AC) des matériaux composites. L’étude expérimentale des relations structure-propriétés est complétée par un travail de modélisation des propriétés diélectriques et de la conductivité thermique des matériaux composites
The integration of renewable energies to the power grid requires its modification in order to ensure its stability, security and efficiency. Improving ultra-high voltage alternative current (UHVAC) gas insulated substations (GIS), e.g. reducing their size or increasing their voltage, is one of the challenges induced by the development of the future power grid, the supergrid. Increasing the ability of solid insulators used in such equipment to withstand electro-thermal stress has been identified as the main obstacle to overcome. The work presented in this manuscript has been motivated by the necessity to develop more efficient electrical insulating materials compared to commercially available ones. An epoxy-anhydride matrix filled with micron sized alumina, often used to produce GIS solid insulators, has been used as a reference for this study. We decided to keep the matrix of the reference material throughout our work and to concentrate on the filler influence in order to optimize the properties of the composites. The impact of the nature of the filler (alumina or hexagonal boron nitride), its shape factor (platelets or almost spherical particles) and its volume fraction upon thermal conductivity, coefficient of thermal expansion, dynamic mechanical properties, dielectric properties, high voltage direct current (DC) conductivity and AC breakdown strength have been highlighted. The experimental study of structure-property relationships is completed by dielectric properties and thermal conductivity modelling using the effective medium theory

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Vogelsang, Ruben. "Time to breakdown of high voltage winding insulations with respect to microscopic properties and manufacturing qualities /." [S.l.] : [s.n.], 2004. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15656.

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Elbuzedi, Mohamed. "Material study and properties of polymers used in composite high voltage insulators." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/17749.

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Thesis (MSc)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: Silicone rubber, particularly poly(dimethylsiloxane) (PDMS), has been increasingly used in the manufacture of outdoor high voltage insulators in the recent years. PDMS offers several advantages that make it suitable for outdoor use, such as low weight, a hydrophobic surface, stability, and excellent performance in heavily polluted environments. PDMS surfaces can, however, become progressively hydrophilic due to surface oxidation caused by corona discharge, UV radiation and acid rain. In this study, PDMS samples of controlled formulations as well as six commercial insulator materials four PDMS based and two ethylene propylene diene monomer (EPDM) based were exposed to various accelerated weathering conditions for various periods of time in order to track changes in the material over time. The ageing regimes developed and used to simulate the potential surface degradation that may occur during in-service usage included needle corona and French corona ageing, thermal ageing, UV-B irradiation (up to 8000 hours) and acid rain (up to 200 days). Both the chemical and physical changes in the materials were monitored using a wide range of analytical techniques, including: static contact angle measurements (SCA), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), gas chromatography (GC), gas chromatography/mass spectroscopy (GC/MS), size-exclusion chromatography (SEC), Fourier-transform infrared photoacoustic spectroscopy (FTIR-PAS) and slow positron beam techniques (PAS). A low molecular weight (LMW) uncrosslinked PDMS model compound was used to further study the chemical effects of corona exposure on PDMS materials. PDMS showed far better performance than EPDM, in terms of resistance to the various ageing regimes and “hydrophobicity recovery”.
AFRIKAANSE OPSOMMING: Silikoonrubber, spesifiek polidimetielsiloksaan (PDMS), is gedurende die afgelope paar jaar toenemend gebruik in die vervaardiging van buitelughoogspanningisolators. PDMS het baie voordele vir gebruik in elektriese isolators soos ‘n laer massa, ŉ hidrofobiese oppervlak, stabiliteit en uitstekende werking in hoogsbesoedelde omgewings. Die hidrofobiese oppervlakte kan egter gelydelik hidrofilies word weens oppervlakoksidasie as gevolg van korona-ontlading, UV-bestraling en suurreën. In hierdie studie is PDMS monsters van verskillende samestellings sowel as ses kommersiële isolators (vier PDMS en twee etileenpropileenrubber (EPDM)) blootgestel aan verskillende versnelde weersomstandighede vir verskillende periodes om die veranderinge in die materiale te monitor. Die verskillende materiale is gerangskik volgens hulle werking oor ‘n periode van tyd. Dit het ook ‘n geleentheid gebied om die eienskappe van die verskillende samestellings te bestudeer. Die tegnieke wat ontwikkel is om die moontlike oppervlakdegradasie te simuleer, het naald-korona, “French” korona, UVB-bestraling (tot 8000 uur) en suurreën (tot 200 dae) ingesluit. Beide die chemiese en die fisiese veranderinge in die materiale is gemonitor met behulp van verskeie tegnieke soos statiese kontakhoekbepaling, optiese mikroskopie, skandeerelektronmikroskopie, energieverspreidingsspektroskopie, gaschromatografie, grootte-uitsluitingschromatografie, foto-akoestiese Fouriertransforminfrarooi (PASFTIR) en stadige-positronspektroskopie (PAS). ŉ Lae molekulêre massa PDMS modelverbinding is gebruik om die chemiese effek van korona te bestudeer. Die PDMS materiale het baie beter vertoon teenoor die EPDM materiale in terme van hulle herstel van hidrofobisiteit.

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Abraham, Berhane Teclesenbet. "Degradation and recovery of polydimethylsiloxane (PDMS) based composites used as high voltage insulators." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49902.

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Thesis (MSc)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: Polydimethylsiloxane (PDMS) compounds are utilized in outdoor high voltage insulation due to their low weight, vandalism resistance, better anti-contamination performance and their superior hydrophobic nature. Under severe environmental conditions and over prolonged service time, however, the hydrophobic surface can gradually become hydrophilic and then recover with adequate resting period. In this study, room temperature vulcanized (RTV) PDMS samples were prepared with different formulations and then exposed to corona discharge to evaluate its effect. The influence of different additives, such as different types and amount of fillers and additionally added low molar mass silicone oils, on the hydrophobicity recovery of the material was investigated. The effects of two types of corona treatment were also evaluated. Hydrophobicity recovery of corona and UV-C aged PDMS samples was evaluated by means of static contact angle measurements. Positron annihilation spectroscopy (PAS) gave important information on the micro structural change after corona treatment of RTV PDMS as well as naturally aged high temperature vulcanized (HTV) PDMS samples. The different formulations of the RTV PDMS samples and the effect of the additives were studied with this technique. The formation of a thin, highly crosslinked inorganic silica-like (SiOx) layer was confirmed even at the early stage of degradation. It was also possible to estimate the thickness of the silica-like layer formed during corona exposure that is responsible for the loss and recovery of hydrophobicity. The surface hardness and hydrophilicity change of PDMS samples due to corona treatment were studied simultaneously with force distance measurements by atomic force microscopy (AFM). The adhesive force calculated from the pull-off force-distance curves showed that the adhesive force between the probe and the sample decreased with increasing corona treatment time, indicating hydrophobicity recovery. In addition to this, the increase in hardness after corona exposure provides indirect evidence of the formation of a silica-like layer. In all cases the hydrophilicity and the surface hardness of the PDMS samples increased directly after corona treatment and recovered with time. Two types of FTIR spectroscopy were used to analyse the surface of the polymer.
AFRIKAANSE OPSOMMINGS: Polidimetielsiloksaan (PDMS) word in buitelug hoogspanninginsulasie gebruik as gevolg van sy lae massa, weerstand teen vandalisme, verbeterde anti-kontaminasie werkverrigting en superieure hidrofobiese karakter. Die hidrofobiese oppervlakte kan egter gelydelik hidrofillies word onder uiterste omgewingsomstandighede en oor langdurige dienstyd. PDMS materiaal herstel egter nadat dit genoeg rustyd toegelaat is. Kamertemperatuur-gevulkaniseerde (KTV) PDMS met verskillende formulasies is in hierdie studie voorberei, aan korona ontlading blootgestel, geëvalueer en vergelyk. Die invloed van bymiddels soos verskillende tipes en hoeveelhede vuiler, asook addisionele lae molekulêre massa silikoonolie, op die herstel van hidrofobisiteit van die materiaal is ondersoek. Twee verskillende metodes van korona behandeling is ook geëvalueer. Die herstel van hidrofobisiteit van korona en UV-C verouderde PDMS monsters is met statiese kontakhoekmeting geëvalueer. Positronvernietigingspektroskopie (PVS) is 'n kragtige tegniek wat belangrike inligting oor die mikrostrukturele verandering van korona behandelde van KTV PDMS sowel as natuurlik-verouderde hoë temperatuur gevulkaniseerde (HTV) PDMS monsters gee. Die verskillende formulasies van die KTV PDMS monsters, sowel as die effek van die vullers, is met behulp van hierdie tegniek ondersoek. Die vorming van 'n dun, hoogskruisgebinde, anorganiese silika-agtige (SiOx) laag op die PDMS oppervlak, selfs tydens die vroeë stadium van degradasie, is bevestig. Dit was ook moontlik om die dikte van die silika-agtige laag wat gedurende die korona blootstelling gevorm het, en wat verantwoordelik is vir die verlies aan hidrofobisiteit, te bepaal. Die oppervlakhardheid en hidrofilisiteit verandering van PDMS monsters as gevolg van korona behandeling, was gelyktydig met krag-afstand metings deur middel van atoomkragmikroskopie (AKM) bestudeer. Die kleefkrag, soos bereken van aftrek kragafstandkurwes, dui daarop dat kleefkragte tussen die taster en die monster afneem met toenemende korona behandelingstyd, wat beduidend is op die herstel van hidrofobisiteit. Daarbenewens is die toename van oppervlakhardheid na korona blootstelling "n indirekte bewys van die formasie van 'n silika-agtige laag. In alle gevalle het die hidrofilisiteit en die oppervlakhardheid van die PDMS monsters toegeneem direk na afloop van korona behandeling en gevolglik herstel met tyd. Twee tipes IR spektroskopie metodes is gebruik vir die chemiese-oppervlak analises

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Kiiza, Respicius Clemence. "The Effect of HV Impulses on Partial Discharge Activity and on the Dielectric Response in Oil-impregnated Paper Insulation." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-142027.

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This work investigates how HV impulses affect the behavior of partial discharge (PD) activity and the low voltage dielectric response of oil-impregnated paper insulation. It also investigates how the change in the PD activity is related to the degradation level of oil-impregnated paper insulation. In order to accomplish these objectives, the ageing were done under three different electrical stress conditions, i.e. HV impulses following an early stage 50 Hz AC PD activity, a prolonged PD activity at a 50 Hz AC stress alone, and a combination of HV impulses and a prolonged PD activity at a 50 Hz AC stress. In order to predict the level of deterioration caused by each ageing stress condition, the dielectric spectroscopy (DS) measurements in a frequency range of 1.0 mHz to 1.0 kHz were performed before and after subjecting a test object to each of the ageing stress conditions. The investigations were mainly done on the test samples consisting of a cavity deliberately introduced between the layers of oil-impregnated paper. Additionally, the investigation about the effect of HV impulses alone on the DS results was done on aged oil-impregnated paper transformer bushing. The PD experimental results presented in this thesis indicate that HV impulses below the impulse breakdown stress following an early stage AC PD activity will neither cause a significant change in phase resolved partial discharge (PRPD) patterns nor damage oil-impregnated paper insulation to a level that can be noticed with visual observations. On the other hand, a prolonged PD activity at a 50 Hz AC stress can cause the change in PRPD patterns by decreasing the total PD charge and the number of PD pulses, but cannot quickly damage the oil-impregnated paper insulation as it would do when it is combined with HV impulses. In addition to that, the results show that the combination of both, HV impulses and a prolonged PD activity at a 50 Hz AC stress can cause a high drop in the PD parameters (total PD charge and number of PD pulses). The DS results show that HV impulses below the impulse breakdown stress following an early stage 50 Hz AC PD activity will not cause a significant increase in the real part of the complex capacitance and in the dissipation factor as they will do when they are combined with a prolonged PD activity at a 50 Hz AC stress. Further, the dielectric spectroscopy results obtained every three hours during the ageing of oil-impregnated paper insulation by a prolonged PD activity at an AC stress show that the dissipation factor will increase, but the PD parameters (total PD charge and the repetition rate) will decrease with time of PD application. For a case of the aged oil-impregnated paper transformer bushing, HV impulses of amplitudes up to 200 kV did not result in the change in the dissipation factor curve before removing insulating oil from the bushing. However, after removing about 2.5 liters of insulating oil from the bushing, HV impulses resulted in the change in the dissipation factor curve. The magnitudes of the dissipation factor curves appeared to be much higher in the middle frequencies region, i.e. the frequencies between 10 mHz and 100 Hz. After refilling the bushing with the same insulating oil, the loss peak shifted towards the higher frequencies. To understand how the ageing by-products initiated by PDs in the small cavity can modify the geometry of oil-impregnated paper insulation; the model of oil-impregnated paper insulation, comprising of a small cavity, was implemented in Finite Element Method (FEM) software (COMSOL Multiphysics 4.2a). The comparison between the simulation and experimental results show that PD by-products will result in two zones, i.e. aged and unaged zones, and the aged zone will grow with time of PD application; thereby increasing the dissipation factor. On the other hand, in order to interpret the change in the dissipation factors for the dielectrics in aged oil-impregnated paper transformer bushing after had been exposed to HV impulses, a model of a part of the condenser body (oil-paper insulation) was also implemented in the FEM software (COMSOL Multiphysics 4.2a). To model a condition of low insulating oil level in the bushing, a part of oil subdomains was replaced with the air dielectric properties. A comparison between the simulation and experimental dissipation factor curves indicate that HV impulses will produce the by-products (ions), which will increase the conductivity of air when the bushing has low insulating oil level. On refilling the bushing with the same insulating oil, the insulating oil will take these ions and the reactions between the aged insulating oil by-products (such as acids) and the ions, may produce more ions, thereby increasing further the conductivity of the insulating oil.

QC 20140303

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Razavi, Borghei Seyyed Moein. "The Modeling of Partial Discharge under Fast, Repetitive Voltage Pulses Using Finite-Element Analysis." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/98001.

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By 2030, it is expected that 80% of all electric power will flow through power electronics systems. Wide bandgap power modules that can tolerate higher voltages and currents than silicon-based modules are the most promising solution to reducing the size and weight of power electronics systems. These wide-bandgap power modules constitute powerful building blocks for power electronics systems, and wide bandgap-based converter/power electronics building blocks are envisaged to be widely used in power grids in low- and medium-voltage applications and possibly in high-voltage applications for high-voltage direct current and flexible alternating current transmission systems. One of the merits of wide bandgap devices is that their slew rates and switching frequencies are much higher than silicon-based devices. However, from the insulation side, frequency and slew rate are two of the most critical factors of a voltage pulse, influencing the level of degradation of the insulation systems that are exposed to such voltage pulses. The shorter the rise time, the shorter the lifetime. Furthermore, lifetime dramatically decreases with increasing frequency. Thus, although wide bandgap devices are revolutionizing power electronics, electrical insulating systems are not prepared for such a revolution; without addressing insulation issues, the electronic power revolution will fail due to dramatically increased failure rates of electrification components. In this regard, internal partial discharges (PDs) have the most effect on insulation degradation. Internal PDs which occur in air-filled cavities or voids are localized electrical discharges that only partially bridge the insulation between conductors. Voids in solid or gel dielectrics are challenging to eliminate entirely and may result simply during manufacturing process. The objective of this study is to develop a Finite-Element Analysis (FEA) PD model under fast, repetitive voltage pulses, which has been done for the first time. The model is coded and implemented in COMSOL Multiphysics linked with MATLAB, and its simulation results are validated with experimental tests. Using the model, the influence of different parameters including void shape, void size, and void air pressure on PD parameters are studied.
M.S.
To decarbonize and reduce energy consumption for commercial aviation, the development of lightweight and ultra-efficient all-electric powertrain including electric motors, drives, and associated thermal management systems has been targeted. Using wide bandgap (WBG) power modules that can tolerate high voltages and currents can reduce the size and weight of the drive. However, the operation of WBG-based power converter can endanger the reliability of the electrified systems, most importantly, the insulation system. In this study, it is attempted to model the impact of such threats to the insulation system using numerical models.

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Mouton, Gerton Nicolaas Jacobus. "An evaluation of different material line insulators under high voltage AC and bipolar DC excitation in a marine polluted environment." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71940.

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Thesis (MScEng)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: The worldwide increase in the popularity of high voltage direct current (HVDC) power transmission application has led to questions regarding the performance of high voltage alternating current (HVAC) insulators when energized under HVDC excitation. These questions have led researchers conduct numerous research projects worldwide. A particular question NamPower (the power utility in Namibia) has faced is: how do these insulators perform and age when energized under HVDC excitation in heavily polluted environments? This question was only partly answered by some insulator ageing tests conducted under laboratory conditions for HVDC excitation. However, the natural ageing tests on insulators, which are preferred, have to date been confined predominantly to HVAC excitation voltages. Thus, this research was initiated to investigate the natural ageing performance of insulators under both HVAC and HVDC excitations, when subjected to harsh marine pollution environments. This research project involved performance and ageing tests on three identical sets of line insulators made from different insulator materials, energised under HVAC and both polarities HVDC excitations respectively. The tests were conducted at Koeberg insulator pollution test station (KIPTS), which is a natural marine pollution insulator test station located near Cape Town, along the west coast of South Africa, approximately 50 m from the sea. The set of insulators consisted of EPDM silicone alloy rubber, HTV silicone rubber, RTV silicone rubber coated porcelain, Porcelain and Glass insulators. The HVAC excitation voltage was chosen as 12.7 kV r.m.s. phase-to-ground and it was decided to use a HVDC excitation voltage equal to this value. The research results showed that the insulators made from HTV silicone rubber performed better than the insulators made from EPDM silicone alloy rubber under all excitation voltages. It is also showed that RTV silicone rubber coated porcelain insulators performed better than Glass and Porcelain insulators under all excitation voltages.
AFRIKAANSE OPSOMMING: Die wêreld wye toename in gewildheid van hoë spanning gelyk stroom (HSGS) krag transmisie aplikasie het gelei na vrae oor die effektieweteit van hoë spanning wissel stroom (HSWS) insolators in HSGS aplikasies. Hierdie vrae het gelei na baie navorsings projekte. Een vraag waarmee NamPower (die krag voorsienings maatskapy in Namibia) gekonfronteer was, was hoe gaan die insolators wat onderworpe is aan ’n HSGS toevoer reageer in ’n baie besoedelde omgewing. Hierdie vraag was slegs gedeeltelik beantwoord deur verouderings toetse op insolators wat gedoen is in ’n labaratorium met ’n HSGS toevoer. Inteendeel, die meeste natuurlike verouderings toetse op insolators, soos verkies, is meestal gedoen met ’n HSWS toevoer. Om hierdie rede was hierdie navorsing begin om natuurlike verouderings toetse te doen op insolators onderworpe beide aan HSWS en HSGS toevoere binne ’n marien besoedelde omgewing. Hierdie navorsings projek gaan oor prestering en verouderings toetse op drie, identiese, transmissie lyn insolator stelle, wat onderskeidelik onderworpe was aan HSWS en beide polariteite HSGS toevoere. Die toetse was gedoen by Koeberg insolator besoedeling toets stasie (KIBTS) wat naby Kaapstad geleë is langs die weskus van Suid Africa omtrent 50 m van die see. ’n Stel toets insolators bestaan uit EPDM silikon allooi rubber, HTV silikon rubber, RTV silikon rubber bedekte porselein, Porselein en Glas insolators. Die HSWS waarde waarmee die insolators getoets was, was 12.7 kV w.g.k., fase-na-grond, en dit was besluit om ’n HSGS waarde gelyk aan hierdie spannings waarde te gebruik. Die navorsings resultate wys dat insolators wat gemaak is met HTV silikon rubber presteer beter as insolators wat met EPDM silikon allooi rubber gemaak is onder al die verskillende toevoere. Dit wys ook dat RTV silikon rubber bedekte porselein presteer beter as Porselein en Glas insolators onder al die verskillende toevoere.

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Am, Sokchea. "Power modules design and optimization for medium power of MMC inverters : high insulation voltage gate driver system and 3D packaging." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT095/document.

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Dans cette recherche, l'auteur met l'accent à la fois sur une optimisation de la conception pour une (MV-MMC: Medium Voltage Modular Multilevel Converter) utiliser comme un DC/AC ou AC/DC et à deuxième fois sur la grille pour les modules IGBT qui sont utilisés dans ce type d'application. Par exemple, les convertisseurs de MMC sont utilisés dans les systèmes d'alimentation des navires électriques avec les buses de moyenne tension de courant continu (en anglais: medium-voltage direct current (MVDC)). Pour une telle application, selon le document IEEE, la tension du bus DC peut être jusqu'à 35kV. Par conséquent, les systèmes de commande rapprochée pour piloter le grille des modules IGBT pour les applications MVDC-MMC sont des principaux problèmes en termes d'architectures et des besoins de haute isolation galvanique. Ainsi, cette thèse fournit des solutions pour répondre à ces problèmes. L'étude inclut également les études d'un matériau diélectrique qui est utilisé comme matériau d'isolation. Les résultats des essais expérimentaux d'un matériau diélectrique proposé pour différentes épaisseurs des couches pour maintenir des niveaux de tension d'isolation sont également fournis pour valider clairement cette étude. En effet, un convertisseur MMC compose d'un certain nombre de cellules de conversion connectés en série. Une cellule (sous-module de convertisseur) est classiquement constitué de deux modules IGBT. Sur la base de la topologie de la cellule, l'architecture d'un pilote de grille contestée pour les modules de puissance à semi-conducteurs est proposée et comparée à celle classique en termes de besoins des niveaux de tension d'isolation galvanique, la taille de la cellule de convertisseur, etc
In this research, the author focuses on both a design optimization for a Medium Voltage Modular Multilevel Converter (MV-MMC) use as a DC/AC or AC/DC converter and gate drivers systems for IGBT modules which are used in this kind of application. For example, the MMC converters are used in Medium-Voltage Direct Current (MVDC) electrical ship power systems. For such application, according to IEEE document, the DC bus voltage can be up to 35kV. Hence, gate drivers’ systems for IGBT modules for MVDC-MMC applications are major concerns in terms of architectures and insulation voltage capabilities. Thus, this dissertation provides solutions to answer these problems. The study also includes the studies of a dielectric material which is used as insulation material. The results of experimental tests of a proposed dielectric material for different layers thicknesses to sustain different insulation voltage levels are also provided to clearly validate this study. Actually, a MMC converter composes of a number of converter cells connected in series. One cell (converter’s sub-module) is classically composed of two IGBT modules. Based on the cell topology, a challenged gate driver’s architecture for power semiconductor modules is proposed and compared to the classical one in terms of high and low galvanic insulation voltage levels’ requirements, converter’s cell size, etc

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Mogniotte, Jean-François. "Conception d'un circuit intégré en SiC appliqué aux convertisseur de moyenne puissance." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0004/document.

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L’émergence d’interrupteurs de puissance en SiC permet d’envisager des convertisseurs de puissance capables de fonctionner au sein des environnements sévères tels que la haute tension (> 10 kV ) et la haute température (> 300 °C). Aucune solution de commande spécifique à ces environnements n’existe pour le moment. Le développement de fonctions élémentaires en SiC (comparateur, oscillateur) est une étape préliminaire à la réalisation d’un premier démonstrateur. Plusieurs laboratoires ont développé des fonctions basées sur des transistors bipolaires, MOSFETs ou JFETs. Cependant les recherches ont principalement portées sur la conception de fonctions logiques et non sur l’intégration de drivers de puissance. Le laboratoire AMPERE (INSA de Lyon) et le Centre National de Microélectronique de Barcelone (Espagne) ont conçu un MESFET latéral double grille en SiC. Ce composant élémentaire sera à la base des différentes fonctions intégrées envisagées. L’objectif de ces recherches est la réalisation d’un convertisseur élévateur de tension "boost" monolithique et de sa commande en SiC. La démarche scientifique a consisté à définir dans un premier temps un modèle de simulation SPICE du MESFET SiC à partir de caractérisations électriques statique et dynamique. En se basant sur ce modèle, des circuits analogiques tels que des amplificateurs, oscillateurs, paires différentielles, trigger de Schmitt ont été conçus pour élaborer le circuit de commande (driver). La conception de ces fonctions s’avère complexe puisqu’il n’existe pas de MESFETs de type P et une polarisation négative de -15 V est nécessaire au blocage des MESFETs SiC. Une structure constituée d’un pont redresseur, d’un boost régulé avec sa commande basée sur ces différentes fonctions a été réalisée et simulée sous SPICE. L’ensemble de cette structure a été fabriqué au CNM de Barcelone sur un même substrat SiC semi-isolant. L’intégration des éléments passifs n’a pas été envisagée de façon monolithique (mais pourrait être considérée pour les inductances et capacités dans la mesure où les valeurs des composants intégrés sont compatibles avec les processus de réalisation). Le convertisseur a été dimensionné pour délivrer une de puissance de 2.2 W pour une surface de 0.27 cm2, soit 8.14 W/cm2. Les caractérisations électriques des différents composants latéraux (résistances, diodes, transistors) valident la conception, le dimensionnement et le procédé de fabrication de ces structures élémentaires, mais aussi de la majorité des fonctions analogiques. Les résultats obtenus permettent d’envisager la réalisation d’un driver monolithique de composants Grand Gap. La perspective des travaux porte désormais sur la réalisation complète du démonstrateur et sur l’étude de son comportement en environnement sévère notamment en haute température (> 300 °C). Des analyses des mécanismes de dégradation et de fiabilité des convertisseurs intégrés devront alors être envisagées
The new SiC power switches is able to consider power converters, which could operate in harsh environments as in High Voltage (> 10kV) and High Temperature (> 300 °C). Currently, they are no specific solutions for controlling these devices in harsh environments. The development of elementary functions in SiC is a preliminary step toward the realization of a first demonstrator for these fields of applications. AMPERE laboratory (France) and the National Center of Microelectronic of Barcelona (Spain) have elaborated an elementary electrical compound, which is a lateral dual gate MESFET in Silicon Carbide (SiC). The purpose of this research is to conceive a monolithic power converter and its driver in SiC. The scientific approach has consisted of defining in a first time a SPICE model of the elementary MESFET from electric characterizations (fitting). Analog functions as : comparator, ring oscillator, Schmitt’s trigger . . . have been designed thanks to this SPICE’s model. A device based on a bridge rectifier, a regulated "boost" and its driver has been established and simulated with the SPICE Simulator. The converter has been sized for supplying 2.2 W for an area of 0.27 cm2. This device has been fabricated at CNM of Barcelona on semi-insulating SiC substrate. The electrical characterizations of the lateral compounds (resistors, diodes, MESFETs) checked the design, the "sizing" and the manufacturing process of these elementary devices and analog functions. The experimental results is able to considerer a monolithic driver in Wide Band Gap. The prospects of this research is now to realize a fully integrated power converter in SiC and study its behavior in harsh environments (especially in high temperature > 300 °C). Analysis of degradation mechanisms and reliability of the power converters would be so considerer in the future

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39

Vosloo, Wallace L. (Wallace Lockwood). "A comparison of the performance of high-voltage insulator materials in a severely polluted coastal environment." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52625.

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Thesis (PhD)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: The main aim of this research programme was to compare the relative performance of different insulator materials used in South Africa when subjected to a severe marine pollution environment. A test programme and procedure, test facility and instrumentation were established. Some novel instrumentation and monitoring equipment were developed and built specifically for this research programme, supported by data analysing software programs. In order to compare material performance only, all non-material design variables between the test insulators had to be removed (e.g. creepage distance, connecting length, inter-shed spacing, profile, etc.). To achieve this some of the test insulators had to be specially manufactured. Leakage current, electrical discharge activity, climatic and environmental data was collected successfully over a one-year test period, starting with new test insulators. The peak and energy values of the leakage current were identified as the two main parameters needed to describe the leakage current activity on the test insulators. A correlation was found between the climatic and environmental data and the leakage current data, and it was found that the leakage current can be determined successfully from some of the climatic and environmental parameters monitored by using multiple regression techniques. Surface conductivity and energy were found to be the best parameters to show the maximum and continuous interaction of the insulator material surface with the electrolytic pollution layer. A natural ageing and pollution test procedure was developed, which has become a South African standard and is gaining international acceptance. A model and hypothesis are proposed to describe the electrical discharge activity that takes place on the test insulators and explain the difference in leakage current performance of the various materials. Keywords: Insulator, Pollution, High Voltage, Leakage current, Material performance.
AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie navorsingsprogram was om die relatiewe prestasie van verskillende isolatormateriale wat in Suid-Afrika gebruik word te vergelyk in 'n swaar besoedelde marine omgewing. 'n Toetsprogram en prosedure, toets fasiliteit en instrumentasie is gevestig. 'n Paar nuwe instrumente en moniteer toerusting is ontwikkel en gebou spesifiek vir hierdie navorsingsprogram, gesteun deur data analise sagteware programme. Ten einde slegs materiaalprestasie te vergelyk, moes alle nie-materiaal ontwerpsveranderlikes tussen die toetsisolators verwyder word (bv. kruipafstand, konnekteer lengte, tussen-skerm spasiëring, profiel, ens.). Om dit reg te kry moes sommige van die toetsisolators spesiaal vervaardig word. Lekstroom, elektriese ontladingsaktiwiteit, klimaat en omgewingsdata is suksesvol versameloor 'n een-jaar toetsperiode, beginnende met nuwe toets isolators. Die piek en energie waardes van die lekstroom is identifiseer as die twee hoof parameters wat nodig is om die lekstroomaktiwiteit op die toetsisolators te beskryf. 'n Korrelasie is gevind tussen die klimaat- en omgewingsdata en die lekstroom data, en dit is gevind dat die lekstroom data suksesvol bepaal kan word van sekere van die klimaat- en omgewingsparameters wat gemoniteer is deur veelvoudige regressie tegnieke te gebruik. Oppervlakskonduktiwiteit en energie is gevind die beste parameters te wees om die maksimum en kontinue interaksie van die isolatormateriaaloppervlak met die elektrolitiese besoedelingslaag aan te toon. 'n Natuurlike veroudering en besoedeling toetsprosedure is ontwikkel, wat 'n Suid-Afrikaanse standaard geword het en besig is om internastionale aanvaarding te wen. 'n Model en hipotese word voorgestelom die elektriese ontladingsaktiwiteit wat op die toetsisolators plaasvind te beskryf en om die verskil in lekstroomprestasie van die verskeie materiale te verduidelik. S/eufelwoorde: Isolator, Besoedeling, Hoog Spanning, Leek stroom, Materiaal prestasie.

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40

Que, Weiguo. "Electric Field and Voltage Distributions along Non-ceramic Insulators." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1037387155.

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41

Eisel, Thomas. "Cooling of electrically insulated high voltage electrodes down to 30 mK." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-77442.

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The Antimatter Experiment: Gravity, Interferometry, Spectroscopy (AEGIS) at the European Organization for Nuclear Research (CERN) is an experiment investigating the influence of earth’s gravitational force upon antimatter. To perform precise measurements the antimatter needs to be cooled to a temperature of 100 mK. This will be done in a Penning trap, formed by several electrodes, which are charged with several kV and have to be individually electrically insulated. The trap is thermally linked to a mixing chamber of a 3He-4He dilution refrigerator. Two link designs are examined, the Rod design and the Sandwich design. The Rod design electrically connects a single electrode with a heat exchanger, immersed in the helium of the mixing chamber, by a copper pin. An alumina ring and the helium electrically insulate the Rod design. The Sandwich uses an electrically insulating sapphire plate sandwiched between the electrode and the mixing chamber. Indium layers on the sapphire plate are applied to improve the thermal contact. Four differently prepared test Sandwiches are investigated. They differ in the sapphire surface roughness and in the application method of the indium layers. Measurements with static and sinusoidal heat loads are performed to uncover the behavior of the thermal boundary resistances. The thermal total resistance of the best Sandwich shows a temperature dependency of T-2,64 and is significantly lower, with roughly 30 cm2K4/W at 50 mK, than experimental data found in the literature. The estimated thermal boundary resistance between indium and sapphire agrees very well with the value of the acoustic mismatch theory at low temperatures. In both designs, homemade heat exchangers are integrated to transfer the heat to the cold helium. These heat exchangers are based on sintered structures to increase the heat transferring surface and to overcome the significant influence of the thermal resistance (Kapitza resistance). The heat exchangers are optimized concerning the adherence of the sinter to the substrate and its sinter height, e.g. its thermal penetration length. Ruthenium oxide metallic resistors (RuO2) are used as temperature sensors for the investigations. They consist of various materials, which affect the reproducibility. The sensor conditioning and the resulting good reproducibility is discussed as well.

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42

Shifidi, S. K. "Modelling and performance evaluation of an HV impulse test arrangement with HVDC bias." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2722.

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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: From a systems operation and design perspective, it is important to understand the behaviour of HVDC system insulation when presented with high voltage transients, such as induced by lightning and switching operations. Therefore, this thesis investigates the design, operation and performance of a circuit arrangement that can be used in high voltage laboratories to generate impulse voltage waveforms superimposed on a dc bias voltage. The circuit arrangement consists of an impulse generator and a dc source that supplies continuous dc voltage to stress the test object, which can be any type of insulator, i.e. composite, porcelain, glass, gap arrangements, etc. The composite waveform obtained from the test arrangement is used experimentally to investigate the impulse flashover of insulators. For modelling and analysis purposes, the test circuit was transformed to a Laplace equivalent in order to derive the applicable nodal voltage equations. After substitution of circuit parameter values, the voltage equations are then transformed to time domain equations that predict the time-domain behaviour of the circuit. To validate this mathematical approach, the voltage waveforms obtained with this mathematical model is compared with the waveforms measured under laboratory conditions and also with waveforms simulated with HSPICE software. These comparisons are performed using graphical representations. Good correlation was obtained and the results are presented in this thesis. The final stage of this thesis discusses the application of the designed test arrangement for flashover and withstands tests on a silicon rubber insulator. The determination of the flashover values is done by using the existing statistical methods. The insulator was tested under dry conditions and also under polluted wet conditions for both positive and negative impulses compared to the DC bias voltage polarity. The results show that the dc bias voltage does not affect the total voltage flashover of the insulator significantly. It was also observed that wetting affects the flashover for negative impulse more severely, while the influence of wetting is minimal with positive impulse voltages
AFRIKAANSE OPSOMMING: Vanuit ‘n stelselbedryf en ontwerp perspektief, is dit is belangrik om die gedrag van HSGS stelsels te verstaan wanneer dit onderwerp word aan hoogspanning oorgangsverskynsels soos veroorsaak deur weerlig en skakeloperasies. Daarom ondersoek hierdie tesis die ontwerp, werking en werkverrigting van ‘n stroombaanopstelling wat gebruik kan word in hoogspanningslaboratoriums om impulsspannings gesuperponeer op gelykspanning voorspannings op te wek. Die stroombaan bestaan uit ’n impulsgenerator en ‘n gs-bron wat die langdurige gs-spanning voorsien aan die toetsvoorwerp, wat enige tipe isolator kan wees. bv. porselein, glas, gapings, ens. Die saamgestelde golfvorm wat met die toetsopstelling verkry word, is eksperimenteel gebruik om die impulsoorvonking van isolators te ondersoek. Vir die doel van modellering and analise, is die stroombaan na ‘n Laplace ekwivalent getransformeer om die toepaslike knooppunt spanningsvergelykings af te lei. Na substitusie van die stroombaan parameter waardes, word die spanningsvergelykings getransformeer na die tydgebied vergelykings wat die tydgebied gedrag van die stroombaan voorspel. Om die wiskundige benadering te toets, word die spanningsgolfvorms wat met die wiskundige model voorspel word, vergelyk met golfvorms wat onder laboratorium toestande gemeet is en ook met golfvorms wat met HSPICE programmatuur gesimuleer is. Hierdie vergelykings word gedoen met behulp van grafiese voorstellings. Goeie korrelasie is verkry en die resultate word in die tesis gegee. Die finale stadium van hierdie tesis bespreek die toepassing van die ontwerpte toetsopstelling vir oorvonk- en weerstaantoetse op ‘n silikonrubber isolator. Die bepaling van die oorvonkwaardes word gedoen deur bestaande statistiese metodes te gebruik. Die isolator is onder droë en nat besoedelde toestande gedoen, vir beide positiewe sowel as negatiewe impulse met verwysing na die GS voorspan spanning. Die resultate toon dat die gsvoorspanning nie die oorvonkspanning van die isolator beïnvloed nie. Dit is ook waargeneem dat die benatting die oorvonking neer beïnvloed met ‘n negatiewe impuls terwyl die invloed minimaal is met positiewe impulsspannings.

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Reynes, Hugo. "Conception d'un module électronique de puissance pour application haute tension." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI035.

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Satisfaire les besoins en énergie de manière responsable est possible grâce aux énergies renouvelables, notamment éoliennes et solaires. Cependant ces centres de captation d’énergie sont éloignés dans zones de consommation. Le transport de l’énergie via des réseaux HVDC (haute tension courant continu) permet un rendement et une flexibilité avantageuse face au transport HVAC (haute tension courant alternatif). Ceci est rendu possible grâce aux convertisseurs utilisant l’électronique de puissance. Les récents développements sur les semi-conducteurs à large bande interdite, plus particulièrement le carbure de silicium (SiC) offrent la possibilité de concevoir ces convertisseurs plus simples, utilisant des briques technologiques de plus fort calibre (≤ 10 kV). Cependant le packaging, essentiel à leur bon fonctionnement, ne suit pas ces évolutions. Dans cette thèse, nous explorons les technologies actuelles ainsi que les limites physique et normatives liées au packaging haute tension. Des solutions innovantes sont proposées pour concevoir un module de puissance haute tension, impactant que faiblement les paramètres connexes (résistance thermique, isolation électrique et paramètres environnementaux). Les éléments identifiés comme problématiques sont traités individuellement. La problématique des décharges partielles sur les substrats céramiques métallisés est développée et une solution se basant sur les paramètres géométriques a été testée. Le boitier standard type XHP-3 a été étudié et une solution permettant de le faire fonctionner à 10 kV à fort degré de pollution a été développée
The supply of carbon-free energy is possible with renewable energy. However, windfarms and solar power plants are geographically away from the distribution points. Transporting the energy using the HVDC (High Voltage Direct Current) technology allow for a better yield along the distance and result in a cost effective approach compared to HVAC (High Voltage Alternative Current) lines. Thus, there is a need of high voltage power converters using power electronics. Recent development on wide bandgap semiconductors, especially silicon carbide (SiC) allow a higher blocking voltage (around 10 kV) that would simplify the design of such power electronic converters. On the other hand, the development on packaging technologies needs to follow this trend. In this thesis, an exploration of technological and normative limitation has been done for a high voltage power module design. The main hot spot are clearly identified and innovative solutions are studied to provide a proper response with a low impact on parasitic parameters. Partial Discharges (PD) on ceramic substrates is analyzed and a solution of a high Partial Discharge Inception Voltage (PDIV) is given based on geometrical parameters. The XHP-3 like power modules are studied and a solution allowing a use under 10 kV at a high pollution degree (PD3) is given

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Fors, Jonathan. "Modeling and OpenFOAM simulation of streamers in transformer oil." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-80932.

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Electric breakdown in power transformers is preceded by pre-breakdown events such as streamers. The understanding of these phenomena is important in order to optimize liquid insulation systems. Earlier works have derived a model that describes streamers in transformer oil and utilized a finite element method to produce numerical solutions. This research investigates the consequences of changing the numerical method to a finite volume-based solver implemented in OpenFOAM. Using a standardized needle-sphere geometry, a number of oil and voltage combinations were simulated, and the results are for the most part similar to those produced by the previous method. In cases with differing results the change is attributed to the more stable numerical performance of the OpenFOAM solver. A proof of concept for the extension of the simulation from a two-dimensional axial symmetry to three dimensions is also presented.
Elektriska genomslag i högspänningstransformatorer föregås av bildandet av elektriskt ledande kanaler som kallas streamers. En god förståelse av detta fenomen är viktigt vid konstruktionen av oljebaserad elektrisk isolation. Tidigare forskning i ämnet har tagit fram en modell för fortplantningen av streamers. Denna modell har sedan lösts numeriskt av ett beräkningsverktyg baserat på finita elementmetoden. I denna uppsats undersöks konsekvenserna av att byta metod till finita volymsmetoden genom att implementera en lösare i OpenFOAM. En standardiserad nål-sfär-geometri har ställts upp och ett flertal kombinationer av oljor och spänningar har simulerats. De flesta resultaten visar god överensstämmande med tidigare forskning medan resultat som avviker har tillskrivits de goda numeriska egenskaperna hos OpenFOAM-lösaren. En ny typ av simulering har även genomförts där simulationen utökas från en tvådimensionell axisymmetrisk geometri til tre dimensioner.

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Pavlas, Ondřej. "Návrh uložení vysokonapěťových elektrod projekční sestavy elektronového mikroskopu na izolační tyče." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-433282.

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In it´s first part, this presented master´s thesis focuses on the problematics of actions taking place in dielectric materials and phenomenons on the surface of real insulators placed in electric field. This research is followed by selection and rating of appropriate ceramic materials for the actual design of the metal – ceramic assembly. The greatest emphasis is given to design of the optimal configuration of the insulator and electrode, which is supported by simulations from the software that implements finite element method. Eventually, the high voltage tests of the assembly used for measuring leakage currents are performed.

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Wardman, John Blackburn. "Vulnerability of Electric Power Systems to Volcanic Ashfall Hazards." Thesis, University of Canterbury. Geological Sciences, 2013. http://hdl.handle.net/10092/8014.

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Volcanic eruptions are powerful natural events which impact strongly on society. As human populations grow and expand into volcanically active areas, their exposure and vulnerability to volcanic hazards is also increasing. Of all volcanic hazards, ashfall is the most likely to impact lifelines because of the large areas affected. The widespread dispersal of ash can cause large-scale disruption of vital infrastructure services, aviation, and primary production. Electric power supply is arguably the most crucial of modern infrastructure systems, especially considering the dependence of other sectors on electricity to maintain functionality. During and immediately after ashfalls, electric power systems are vulnerable to a number of impacts, but disruption from volcanic ash-induced insulator flashover (unintended, disruptive electrical discharge) is most common. This thesis investigates the vulnerability of electric power systems to volcanic ashfall by examining impacts to the different sectors of the modern power system and exploring appropriate mitigation strategies. Analogue laboratory trials using a pseudo (synthetic) ash are undertaken to verify the environmental, volcanological and electrical parameters that most affect electrical conductivity and therefore the flashover mechanism in these experiments. While dry ash is highly resistant to the flow of electric current, increasing moisture content, soluble salt load, and compaction (bulk density) will reduce this resistance and, in turn, increase the potential for flashover. Volcanic ash is an acute form of airborne pollution for areas downwind of active volcanoes. Results from laboratory experiments in this thesis suggest that insulator pollution (volcanic ash) performance (dielectric strength) is primarily dictated by (1) the conductivity of the ash, and (2) insulator material, profile (shape) and dimensioning. Composite polymer insulators tested herein effectively minimise sinusoidal leakage current and partial discharge activity and also exhibit higher pollution performance when compared to ceramic equivalents. Irrespective of insulator material, however, the likelihood of flashover increases significantly once the bottom surface of suspension insulator watersheds become contaminated in wet ash. The thesis investigates the vulnerability (hazard intensity/damage ratio) of electric power systems to volcanic ashfall hazards. Identification, analysis, and reduction of the risk of ashfall impacts to power networks is explored as a part of holistic volcanic risk assessment. The findings of the thesis contribute to the readiness, response and recovery protocols for large electric power systems in volcanic disasters; which directly affects the functional operation and economics of industrial and commercial society.

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Pallon, Love. "Polyethylene/metal oxide nanocomposites for electrical insulation in future HVDC-cables : probing properties from nano to macro." Doctoral thesis, KTH, Polymera material, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-193591.

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Nanocomposites of polyethylene and metal oxide nanoparticles have shown to be a feasible approachto the next generation of insulation in high voltage direct current cables. In order to reach an operationvoltage of 1 MV new insulation materials with reduced conductivity and increased breakdown strengthas compared to modern low-density polyethylene (LDPE) is needed.In this work polyethylene MgO nanocomposites for electrical insulation has been produced andcharacterized both from an electrical and material perspective. The MgO nanoparticles weresynthesized into polycrystalline nanoparticles with a large specific surface area (167 m2 g–1). Meltprocessing by extrusion resulted in evenly dispersed MgO nanoparticles in LDPE for the silane surfacemodified MgO as compared to the unmodified MgO. All systems showed a reduction in conductivityby up to two orders of magnitude at low loading levels (1–3 wt.%), but where the surface modifiedsystems were able to retain reduced conductivity even at loading levels of 9 wt.%. A maximuminteraction radius to influence the conductivity of the MgO nanoparticles was theoretically determinedto ca. 800 nm. The interaction radius was in turn experimentally observed around Al2O3 nanoparticlesembedded in LDPE using Intermodulation electrostatic force microscopy. By applying a voltage on theAFM-tip charge injection and extraction around the Al2O3 nanoparticles was observed, visualizing theexistence of additional localized energy states on, and around, the nanoparticles. Ptychography wasused to reveal nanometre features in 3D of electrical trees formed under DC-conditions. Thevisualization showed that the electrical tree grows by pre-step voids in front of the propagatingchannels, facilitating further growth, much in analogy to mechanical crack propagation (Griffithconcept). An electromechanical effect was attributed as possible mechanism for the formation of the voids.
Nanokompositer av polyeten och metalloxidpartiklar anses vara möjliga material att använda i morgondagens isolationshölje till högspänningskablar för likström. För att nå en transmissionsspänning på 1 MV behövs isolationsmaterial som i jämförelse med dagens polyeten har lägre elektrisk ledningsförmåga, högre styrka mot elektriskt genomslag och som kan kontrollera ansamling av rymdladdningar. De senaste årens forskning har visat att kompositer av polyeten med nanopartiklar av metalloxider har potential att nå dessa egenskaper. I det här arbetet har kompositer av polyeten och nanopartiklar av MgO för elektrisk isolation producerats och karaktäriserats. Nanopartiklar av MgO har framställts från en vattenbaserad utfällning med efterföljande calcinering, vilket resulterade i polykristallina partiklar med en mycket stor specifik ytarea (167m2 g-1). MgO-nanopartiklarna ytmodifierades i n-heptan genom att kovalent binda oktyl(trietoxi)silan och oktadekyl(trimetoxi)silan till partiklarna för att skapa en hydrofob och skyddande yta. Extrudering av de ytmodifierade MgO nanopartiklarna tillsammans med polyeten resulterade i en utmärkt dispergering med jämnt fördelad partiklar i hela kompositen, vilket ska jämföras med de omodifierade partiklarna som till stor utsträckning bildade agglomerat i polymeren. Alla kompositer med låg fyllnadsgrad (1–3 vikt% MgO) visade upp till 100 gånger lägre elektrisk konduktivitet jämfört med värdet för ofylld polyeten. Vid högre koncentrationer av omodifierade MgO förbättrades inte de isolerande egenskaperna på grund av för stor andel agglomerat, medan kompositerna med de ytmodifierade fyllmedlen som var väl dispergerade behöll en kraftig reducerad elektrisk konduktivitet upp till 9 vikt% fyllnadshalt. Den minsta interaktionsradien för MgO-nanopartiklarna för att minska den elektriska konduktiviten i kompositerna fastställdes med bildanalys och simuleringar till ca 800 nm. Den teoretiskt beräknade interaktionsradien kompletterades med observation av en experimentell interaktionsradie genom att mäta laddningsfördelningen över en Al2O3-nanopartikle i en polyetenfilm med intermodulation (frekvens-mixning) elektrostatisk kraftmikroskop (ImEFM), vilket är en ny AFM-metod för att mäta ytpotentialer. Genom att lägga på en spänning på AFM-kantilevern kunde det visualiseras hur laddningar, både injicerades och extraherades, från nanopartiklarna men inte från polyeten. Det tolkades som att extra energinivåer skapades på och runt nanopartiklarna som fungerar för att fånga in laddningar, ekvivalent med den gängse tolkningen att nanopartiklar introducera extra elektronfällor i den polymera matrisen i nanokompositer. Nanotomografi användes för att avbilda elektriska träd i tre dimensioner. Avbildningen av det elektriska trädet visade att tillväxten av trädet hade skett genom bildning av håligheter framför den framväxande trädstrukturen. Håligheterna leder till försvagning av materialet framför det propagerande trädet och förenklar på det sättet fortsatt tillväxt. Bildningen av håligheter framför trädstrukturen uppvisar en analogi till propagering av sprickor vid mekanisk belastning, i enlighet med Griffiths koncept.

QC 20161006

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48

Глєбов, Олег Юрійович. "Вдосконалення заземлювальних пристроїв електричних підстанцій для забезпечення безаварійної роботи вторинних кіл." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/40844.

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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.14.02 – електричні станції, мережі та системи. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2019 р. Дисертацію присвячено вдосконаленню заземлювальних пристроїв підстанцій напругою 330(220)/150(110) кВ за критерієм запобігання пошкодження ізоляції кабелів струмових захистів при ударі блискавки та при короткому замиканні на шинах розподільного пристрою вказаних класів напруги. На підставі аналізу експериментальних даних, отриманих на 80 діючих підстанціях України, визначено незалежні фактори, а також незначимі із ряду незалежних. На підставі проведення чьотирьох- та п'ятифакторних експериментів отримано модель для визначення опору заземлювального пристрою. Проведено порівняльний аналіз отриманої моделі з відомими розрахунковими методиками. Значення опору, визначене за формулою нормативного документу, для більшості підстанцій менше, ніж визначене за отриманою моделлю, тому є оцінкою знизу. На підставі проведення шестифакторного експерименту отримано модель для визначення напруги на ізоляції кабелю вторинних кіл трансформатору струму, який є найвіддаленішим від зали релейних панелей, при короткому замиканні на шинах розподільного пристрою. У роботі сформульовано процедуру експериментального визначення напруги на ізоляції кабелю при імітації короткого замикання. У роботі розроблено методику та наведено приклади визначення конструктивних параметрів та матеріальних витрат на виконання заземлювальних пристроїв з використанням отриманих в роботі математичних моделей за критерієм запобігання пошкодження ізоляції кабелів вторинних кіл при короткому замиканні, а також за критерієм запобігання хибного спрацювання струмових захистів у випадку пошкодження ізоляції кабелю.
Thesis for granting the Degree of Candidate of Technical sciences in speciality 05.14.02 – electric stations, networks and systems. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2019. The dissertation is devoted to the improvement of grounding systems of substations with voltage 330 (220) / 150 (110) kV on the criterion of prevention of damage to the insulation of current protection cables with a lightning strike and with short-circuit on the bus of the switchgear of the specified voltage classes. On the basis of the analysis of experimental data obtained at 80 operating substations of Ukraine, independent factors are determined, as well as insignificant from a number of independent ones. On the basis of four- and five-factor experiments, a model was developed to determine the grounding systems resistance. A comparative analysis of the obtained model with known computational methods was carried out. The value of the resistance, determined by the formula of the normative document, for most substations is less than determined by the received model, therefore, is an estimate from below. On the basis of a sixfactor experiment, a model for determining the voltage on the cable insulation of the secondary circuits of the current transformer is obtained, which is the most distant from the relay panels hall, with a short circuit on the bus of the switchgear. In the paper, the procedure for the experimental determination of voltage on cable isolation during simulation of short circuit was developed. In this work a method is developed and examples are given for determination of constructive parameters and material costs of grounding systems with the use of the mathematical models obtained in the work on the criterion of prevention of damage to insulation of secondary circuits with short circuit, and according to the of prevention the false triggering of current protection in the event of damage to the cable insulation.

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49

Глєбов, Олег Юрійович. "Вдосконалення заземлювальних пристроїв електричних підстанцій для забезпечення безаварійної роботи вторинних кіл." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/40840.

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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.14.02 – електричні станції, мережі та системи. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2019 р. Дисертацію присвячено вдосконаленню заземлювальних пристроїв підстанцій напругою 330(220)/150(110) кВ за критерієм запобігання пошкодження ізоляції кабелів струмових захистів при ударі блискавки та при короткому замиканні на шинах розподільного пристрою вказаних класів напруги. На підставі аналізу експериментальних даних, отриманих на 80 діючих підстанціях України, визначено незалежні фактори, а також незначимі із ряду незалежних. На підставі проведення чьотирьох- та п'ятифакторних експериментів отримано модель для визначення опору заземлювального пристрою. Проведено порівняльний аналіз отриманої моделі з відомими розрахунковими методиками. Значення опору, визначене за формулою нормативного документу, для більшості підстанцій менше, ніж визначене за отриманою моделлю, тому є оцінкою знизу. На підставі проведення шестифакторного експерименту отримано модель для визначення напруги на ізоляції кабелю вторинних кіл трансформатору струму, який є найвіддаленішим від зали релейних панелей, при короткому замиканні на шинах розподільного пристрою. У роботі сформульовано процедуру експериментального визначення напруги на ізоляції кабелю при імітації короткого замикання. У роботі розроблено методику та наведено приклади визначення конструктивних параметрів та матеріальних витрат на виконання заземлювальних пристроїв з використанням отриманих в роботі математичних моделей за критерієм запобігання пошкодження ізоляції кабелів вторинних кіл при короткому замиканні, а також за критерієм запобігання хибного спрацювання струмових захистів у випадку пошкодження ізоляції кабелю.
Thesis for granting the Degree of Candidate of Technical sciences in speciality 05.14.02 – electric stations, networks and systems. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2019. The dissertation is devoted to the improvement of grounding systems of substations with voltage 330 (220) / 150 (110) kV on the criterion of prevention of damage to the insulation of current protection cables with a lightning strike and with short-circuit on the bus of the switchgear of the specified voltage classes. On the basis of the analysis of experimental data obtained at 80 operating substations of Ukraine, independent factors are determined, as well as insignificant from a number of independent ones. On the basis of four- and five-factor experiments, a model was developed to determine the grounding systems resistance. A comparative analysis of the obtained model with known computational methods was carried out. The value of the resistance, determined by the formula of the normative document, for most substations is less than determined by the received model, therefore, is an estimate from below. On the basis of a sixfactor experiment, a model for determining the voltage on the cable insulation of the secondary circuits of the current transformer is obtained, which is the most distant from the relay panels hall, with a short circuit on the bus of the switchgear. In the paper, the procedure for the experimental determination of voltage on cable isolation during simulation of short circuit was developed. In this work a method is developed and examples are given for determination of constructive parameters and material costs of grounding systems with the use of the mathematical models obtained in the work on the criterion of prevention of damage to insulation of secondary circuits with short circuit, and according to the of prevention the false triggering of current protection in the event of damage to the cable insulation.

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50

Shirvani, Boroujeni Ali. "Ein Beitrag zum Entladungsverhalten langer Luftfunkenstrecken bei Blitzspannung." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-158163.

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Für die Menschen zählen Gewitter mit Donner und Blitz zu den ältesten bekannten Phänomenen der Natur. Die Tatsache, dass Blitze dennoch bis heute nicht abschließend erforscht sind, liegt in dem äußerst komplexen, schnellen und stochastischen Verhalten der Blitzentladung begründet. Der Autor befasste sich in Rahmen dieser Arbeit u.a. mit der Entwicklung eines modernen Messsystems, durch das die Erfassung von sowohl elektrischen als auch optischen Parametern der im Nanosekundenbereich ablaufenden Prozesse der Entladungen möglich wurde. Es handelt sich um technisch anspruchsvolle Messungen von hohen Stoßspannungen und schwachen Vorentladungsströmen in einem großen Frequenzbereich. Außerdem gelang es durch eine geschickte Synchronisation, die Entladungsprozesse präzise und erstmalig in einer Fotosequenz aufzunehmen. Auf Grundlage der Messergebnisse konnte der Entladungsprozess in mehrere Phasen der Vorentladung unterteilt und beschrieben werden. Vor allem beweisen die Messergebnisse die Existenz einer kanalartigen Vorentladung, die nicht zwingend zu einem Durchschlag führt. Dieser Mechanismus, der bei langsam ansteigenden Spannungen als stabile Leaderentladung benannt und mit Thermoionisation gekennzeichnet ist, war bei Blitzstoßspannungen bisher umstritten
The breakdown behavior of long air gaps by Lightning Voltages has been investigated and the results of a new measurement system are reported. A series of up to eight photos (made by a high-speed camera) have recorded the expansion of discharge activities during the breakdown process. The pre-discharge current and voltage have been measured as well. The modern measurement techniques have made possible the synchronization of the photos with the current and voltage measurements in nanosecond-ranges. The combination of the measured current, voltage, and photos can precisely explain the breakdown process. The experiments have been carried out with the lightning impulses up to 2.4 MV and the air gaps up to 4 m. Despite of such high voltages, the experimental system has been verified to be appropriate for measuring the pre-discharge current in mA-ranges

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