Investigation of the dielectric properties of solid insulation materials stressed with high-frequency high voltage

• Applicant: Professorin Dr. Myriam Koch
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 536682752

As a result of an increased integration of power electronic components in power grids and the increasing availability of wide-bandgap power semiconductors, the demands on solid insulating materials in the field of power engineering are constantly increasing. Both trends lead to the exposure of the insulating materials to higher electric fields and higher frequencies simultaneously resulting in an impact on their short- and long-term behavior, respectively. The current knowledge of the behavior of insulating materials up to a frequency range of a few MHz in combination with high electric fields, as reached by modern power electronic circuits, is not sufficient to derive systematic statements on the resilience, the insulation failure rate or the aging behavior. In particular, the frequency, field strength and temperature dependent dielectric loss mechanisms have to be better understood. Therefore, new approaches and methods in the form of coordinated dielectric and aging studies on selected insulating materials with high-frequency high-voltage stress will be conducted in this project. As a first step, the test setups for generating high-frequency high voltage with frequencies up to 10 MHz and amplitudes up to approx. 20 kV are designed and built up. For frequencies up to 50 kHz, high-frequency high-voltage transformers are used. For frequencies between 50 kHz and 10 MHz, the high-frequency high voltage is generated by series resonant circuits, which are excited into resonance by inverters. In the second step, investigations of the dielectric properties will be carried out on solid insulating materials under the influence of high-frequency high voltage. These investigations focus on a better understanding of the complex relationships between the dielectric and thermal properties and stress factors such as frequency, electric field strength and temperature. In addition to the breakdown field strength, dielectric parameters such as the loss factor and the permittivity will be measured during exposure to high-frequency high voltage via a reference path as a function of field strength and frequency. The aim of the last step is to get a deeper insight into aging behavior of solid insulating materials stressed with high-frequency high voltage. For this purpose, dielectric spectroscopies of the material samples are carried out, both without prior exposure and after exposure to high-frequency high voltage, respectively, in order to characterize the influence of the high-frequency high voltage exposure on the dielectric parameters of the materials. Finally, after aging of the materials, breakdown tests are carried out to draw conclusions on the lifetime characteristics of the respective materials depending on the prior stress (combination of frequency and field strength).

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Volker Hinrichsen