Die vorliegende Arbeit befasst sich mit der Isolationszuverlässigkeit und Lebensdauermodellierung für die Gehäusekonstruktion von Halbleitersensoren. Bei den untersuchten Gehäusekonstruktionen handelt es sich insbesondere um Stromsensoren, die auf der Messung des Magnetfeldes eines stromdurchflossenen Leiters basieren. Dabei werden spannungsinduzierte Fehlermechanismen und ihre Auswirkung innerhalb des Sensors diskutiert und ein Lebensdauermodell für den Sensor beschrieben, das auf dem Fehlermechanismus der anodischen Oxidation basiert.:1 THEORETISCHE GRUNDLAGEN DER SENSORKONSTRUKTION 1.1 Grundlagen der Isolationskoordination 1.2 Grundlagen der Sensorkonzeption 1.3 Stand der Technik 1.4 Aufgaben für die Gehäuseentwicklung 2 SPANNUNGSINDUZIERTE FEHLERMECHANISMEN 2.1 Teilentladung 2.2 Dielektrischer Durchbruch 2.3 Chemische Umsetzung von Si 2.4 Migrationsmechanismen 2.5 Leckstrom 3 LEBENSDAUERMODELLIERUNG 3.1 Beschleunigte Alterung 3.2 Modellfunktion für die Lebensdauer 3.3 Lebensdauerkalkulationen

There is always a need for more compact designs of power transformers free of partial discharges, in order to save cost on the construction and required material resources. The physical geometric constrictions inside the transformer tank would demand field-grading techniques to homogenise the field strength distribution on oil-solid interfaces, when required. Standard filler materials such as carbon black or silicon carbide (SiC) have a too high electrical conductivity yielding an appropriate grading field strength values for air-related applications. Because insulation oil has a higher electrical breakdown strength, the electrical conductivity must be engineered to lower values in order to reach a higher effective grading field strength. This paper presents the investigation of a new material system based on a phenolic resin Lerg FL-500 and the electrically functionalized ceramic filler particles Merck Iriotec®7550 that enable a resistive electrical field grading in insulation oil. In order to verify the principle functionality of the proposed field grading system, a layer is applied on a substrate surface representing possible oil-solid-interface inside oil-filled power transformers. First, the manuscript describes the methods of specimen preparation and the measurement of the nonlinear current-time behaviour under AC voltage stress for different filler contents. Second, a concurring optical and electrical determination of the partial discharge inception and extinction voltage of a modified Toepler arrangement allows the indirect determination of the electrical field strength distribution along the functionalized layer without the need of direct measurement. To do so, the radius of the circular functional layer is varied and with it the specific grading length. In analogy to state of the art SiC-filled systems, a linear dependency between the effective grading length and the PD inception voltage is observed. The quotient of voltage drop over a varied radius yields the effective graded electric field strength.

Freileitungsmaste aus herkömmlichen Beton werden bereits heute in großer Zahl in Mittelspan-nungsnetzen eingesetzt. Im Bereich der Hochspannungsfreileitungen existieren bisher international nur wenige erste Freileitungen mit Masten aus herkömmlichen Beton. Um zukünftig Elektroenergie über große Entfernungen über Trassen mit geringen Flächenbedarf transportieren zu können, sind neue Hochspannungsfreileitungen in kompakter Bauweise notwendig. Um dieses Ziel zu erfüllen, sollen die Kompaktmaste aus ultra-hochfestem Beton (UHPC) hergestellt werden. Dafür ist eine neue Sorte von UHPC mit hoher Festigkeitsklasse zu entwickeln. Die mechanischen, elektrischen und thermischen Eigenschaften des neuen Betonmaterials waren zunächst unbekannt. Bisher gab es kaum Kenntnisse über die elektrischen und thermischen Belas-tungen, die auf die Betonmaste einer Freileitung in kompakter Bauweise einwirken. Ein Teilthema im interdisziplinären Forschungsprojekt „KoHöMaT“ (gefördert durch das Bundesmi-nisterium für Wirtschaft und Energie) war es, gemeinsam mit Forschungsinstituten (IMB, Fichtner, Lapp, Europoles, KIT, iBMB) die Materialparameter des neuen UHPC zu bestimmen. Den Einfluss der elektromagnetischen Belastungen auf die Lebensdauer und die Festigkeit des Ver-bundes aus Stahl und Beton habe ich untersucht. Aufgabe meiner Arbeit ist es auch, die elektrischen und thermischen Eigenschaften, wie die elektrische Leitfähigkeit, die elektrische Festigkeit, die Per-mittivität, den Verlustfaktor und die Wärmeleitfähigkeit experimentell zu bestimmen. Anhand der experimentellen Untersuchungen wurde der Versagensmechanismus des UHPC-Betons bei Span-nungsbelastung identifiziert. Die am Betonmast auftretenden elektrischen und thermischen Belas-tungen wurden mit Hilfe von verschiedenen FEM-Modellen berechnet und den gemessenen Fes-tigkeiten gegenübergestellt. Es wurde der Einfluss permanenter elektrischer Felder auf die mechanischen Eigenschaften des UHPC bestimmt. Hierfür wurde die Druckfestigkeit des Betons vor und nach Dauerversuchen bei verschiedenen Spannungsbelastung gemessen. Der Verbund zwischen Stahl und Beton wurde in Lastwechselversuchen thermisch hoch beansprucht und dessen mechanische Festigkeit vor und nach der thermischen Belastung bei Auszugsversuchen gemessen. Aufgrund der befürchtenden gesundheitlichen Risiken für Menschen und Tiere, sowie der gegen-seitigen Beeinflussung benachbarter elektronischer Systeme (EMV) dürfen die elektromagnetischen Felder von Freileitungen die jeweiligen maximal zulässigen Grenzwerte nicht überschreiten. Ich habe die Berechnungen der elektrischen und magnetischen Feldverteilung für die im Verbundvorhaben entwickelten Mastdesigns durchgeführt. Gemeinsam mit den Forschungsinstituten (Europoles, Fichtner, Lapp) wurden die Mastdesigns hinsichtlich der Feldverteilung optimiert. / The Overhead line towers made of conventional concrete are already used in large numbers in the medium voltage nowadays. So far, only a few towers of overhead transmission line made of con-ventional concrete which exists internationally in the area of high voltage. In order to be able to transmit electrical energy over long distances by routes of less floor space requirements, new high voltage overhead lines in compact construction are necessary. To achieve this goal, the compact towers have to be made of ultra-high-performance concrete (UHPC). Therefore, a new kind of UHPC with a high strength class has to be developed. For this kind of new concrete, the mechanical, electrical and thermal characteristics were unknown till now either, there was rare knowledge about the electric and thermal loads which have an effect on the concrete towers of an overhead line in compact construction method. The main purpose part of this interdisciplinary research project 'KoHöMaT “, which funded by the Federal Ministry for Economic Affairs and Energy), was to identify the material parameters of the new UHPC together with the following research institutes (IMB, Fichtner, Lapp, Europoles, KIT, iBMB). It was examined the influence of electromagnetic loads on the lifetime and its’ strength bond be-tween both of composite steel and concrete, also as my major involve was to determine the elec-trical and thermal properties experimentally, such as electrical conductivity, electrical strength, per-mittivity, dissipation factor and finally thermal conductivity. As a result, the failure mechanism of the UHPC under the electrical stresses has been identified then,the electrical and thermal loads on the concrete towers were calculated by using various FEM models accordingly, the measured values were used in the determination of electrical strength. All mentioned theoretical calculated parameters were compared with the real measured parameters. The influence of permanent electric fields on mechanical properties of the UHPC was determined as well. Mainly, the compressive strength of the concrete was measured before and after durability tests at different voltage loads. In addition, the composite (interface) between steel and concrete was thermal extremely loaded by alternating load tests. Its mechanical strength has been measured by pull-out tests before and after this thermal loads. Due to the fear of health risks for both humans and animals, as well as the mutual influence of neighboring electronic systems (EMV), the electromagnetic fields of open lines must not exceed the respective maximum permissible limit values. The calculations of the electrical and magnetic field distribution were carried out for the mast design developed in the composite project. Together with the other research institute (Europoles, Fichtner, Lapp). the tower designs were optimized with re-gard to the field distribution.

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.

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.