Discharges at DC voltage with superimposed medium frequency voltage at dielectric interfaces in high-voltage-insulation-systems
Final Report Abstract
In the future, the provision of electrical energy will be carried out through decentralized networks where electrical energy is generated, transported, and transformed. These networks can be connected to large transmission lines when needed. In addition to the currently dominant 50 Hz alternating current (AC), direct current (DC) will gain significance as a fundamental voltage form in the future. The coupling of voltage levels and transformation of current forms will be achieved through power electronic topologies, involving high potential differences. Especially in cascaded circuits used in medium and high-voltage networks, highvoltage insulation systems will be subjected to the system voltage, primarily a direct voltage, superimposed with a medium-frequency (tens of kilohertz) sinusoidal or rectangular voltage, as a functional voltage in power electronics. The project’s objective was to gain fundamental insights into the design, implementation, and operation of insulation systems subjected to a medium-frequency high voltage superimposed with a system voltage (direct voltage). Scientific investigations were conducted on fundamental arrangements in high-voltage engineering regarding the ignition, discharge characteristics, and interference potential of discharges under mixed voltages. Partial discharges under direct voltage or low-frequency alternating voltage are relatively non-critical in terms of their interference potential under the influence of relatively small field strengths. The interference potential of discharges under medium-frequency voltage or voltage components is considerably higher. Conditions for discharge initiation, the formation, and shape of discharge patterns under medium-frequency voltage have been rarely addressed in the past literature. Systematic studies on the discharge pattern under mixed voltages with direct and higherfrequency voltage components are not well documented. The focus was on experimental fundamental investigations on representative arrangements with synthesized voltage waveforms to simulate real voltage stress. These investigations focused on discharges in gaseous surroundings, their phenomenology, and effects on surrounding solid (polymeric) insulating materials. Electrical, chemical-physical, and optical investigation methods were applied to describe the phenomenology. The obtained results and insights contribute to the understanding of (partial) discharges under medium-frequency mixed voltages and their effects on insulation systems in technical applications. They serve as a basis for the design and dimensioning of insulation systems for modern and future equipment operating with medium-frequency mixed voltages.
Publications
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Endurance of Polymeric Insulation Foil Exposed to DC-Biased Medium-Frequency Rectangular Pulse Voltage Stress. Energies, 13(1), 13.
Färber, Raphael; Guillod, Thomas; Krismer, Florian; Kolar, Johann & Franck, Christian
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Measurement and Numerical Simulation of Discharge Characteristics in Air at Medium Frequency Voltages. IEEE Transactions on Dielectrics and Electrical Insulation, 28(5), 1506-1513.
Seifert, Florian; Jugelt, Stefan & Leu, Carsten
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„Messung der Oberflächenladung von Polymer-Folien nach Corona-Aufladung mit Mischspannung“, Fachtagung Polymere Isolierstoffe und ihre Grenzflächen, Zittau, Deutschland, 6. / 7. Oktober 2021
Seifert, F.; Pichugin, P.; Töpfer, H. & Leu, C.
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„Wirkungen hoher Spannungsänderungsgeschwindigkeiten auf Isoliermaterialien“; EPCE-Online-Seminar: „Belastungen von Wicklungssystemen durch hohe du/dt“; März 2022
Leu, C.
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„Wirkungen von Entladungen auf dielektrische Grenzflächen bei Gleichspannung und überlagerter mittelfrequenter Wechselspannung”; Technische Universität Ilmenau, Dissertation 2022
Seifert, Florian
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„Aging of Epoxy Insulation under Mixed-Frequency Medium-Voltage and Environmental Stress”, Ph.D. Thesis, ETH Zürich, 2023
Küchler, F.
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„Dielectric Strenght of Epoxy-Air interference under Superimposed AC+DC Voltage”, International Symposium on High Voltage Engineering, Glasgow, August 2023
Borvanov, S.; Leu, C. & Töpfer, H.
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„Optical Investigation on Electrical Discharge Behavior ibn Air under DC Voltage with Superimposed AC “; XXII International Conference on Gas Discharges and their Applications, Greifswald, September 2023
Weise, M. & Leu, C.
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„Partial Discharge Detection in Solids at Medium Frequency Voltages by Vibration Measurement”; International Symposium on High Voltage Engineering, Glasgow, August 2023
Weiland, N.; Weise, M. & Leu, C.
