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TY - THES AU - Vocke, Jan Ludwig TI - Untersuchung von Einflussfaktoren auf die elektrische Festigkeit von Feststoff-Isoliermaterialien bei mittelfrequenter Spannungsbelastung PB - Rheinisch-Westfälische Technische Hochschule Aachen VL - Dissertation CY - Aachen M1 - RWTH-2026-00639 SP - 1 Online-Ressource : Illustrationen PY - 2025 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2026 N1 - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2025 AB - The electrical energy system is currently undergoing a fundamental change, as a result of which power electronic components are increasingly being used in energy transmission and distribution. By using power electronic converters, for example, transformers can be operated at a higher frequency than the grid frequency. In addition to the higher frequency the use of power electronics results in non-sinusoidal voltages, in particular rectangular voltages, are thereby becoming more relevant, resulting in new requirements for the insulation materials used. The aim of this work is therefore to gather basic knowledge about the factors influencing the dielectric strength of solid insulating materials for transformers under medium-frequency voltage stress and, in particular, to compare the influence of sinusoidal and rectangular voltage stresses. For this purpose, the dielectric strength of four insulation materials typical for dry-type transformers at sinusoidal and rectangular voltages in the frequency range 1 kHz to 10 kHz is determined experimentally by varying various factors, such as the DC component. The frequency range investigated is based on the typical operating frequencies for these transformers in power electronic converters. With regard to the investigations on the influence of the DC component, suitable test voltages and their characteristic parameters must first be defined and existing test benches adapted so that these test voltages can be realized. The results show that the DC component is a decisive influencing factor. With regard to the influence of frequency, it can be determined that dielectric strength decreases significantly with increasing frequency. This decrease can be observed essentially for sinusoidal and rectangular, as well as all DC components and materials investigated. For the influence of the voltage shape on the dielectric strength, in respect to the RMS value of the voltage, the results show that the materials show a higher dielectric strength on average when exposed to rectangular voltages than when exposed to sinusoidal voltages. This contradicts the common assumption of higher dielectric losses for non-sinusoidal voltages and their correlation with reduced dielectric strength. Overall, it can be concluded from the results obtained that sinusoidal voltages represent the worst case stress in terms of the RMS value of the electrical short-term strength in the parameter range under consideration. The investigations carried out with sinusoidal stresses therefore allow conservative assumptions to be made with regard to rectangular voltage stresses. However, the results also show that the influence of the voltage shape clearly depends on the output variable under consideration and therefore not only the effective value of the breakdown voltage should be analyzed and taken into account. LB - PUB:(DE-HGF)11 DO - DOI:10.18154/RWTH-2026-00639 UR - https://publications.rwth-aachen.de/record/1025266 ER -