ISBN 9783843957380

978-3-8439-5738-0, Reihe Energietechnik

Patrick Vieth
Experimental Research and Modeling of Plasma Recovery in DC Hybrid Switching Devices

146 Seiten, Dissertation Technische Universität Braunschweig (2025), Softcover, A5

Zusammenfassung / Abstract

The energy transition is essential to limit the rate of global climate change. Direct current (DC)-grids enable a more efficient use and transmission of energy. In contrast to alternating current, DC interruption demands higher requirements. Hybrid switching devices (HSD) combine the advantages of both mechanical (MSD) and semiconductor switching devices (SSD) with high interruption speeds and minimal power loss.

The objective of this work is to analyze the interruption process of LVDC HSDs to allow the optimization of costs and technical properties in the future. The primary objective of this research is to assess the recovery behavior of the MSD in response to the influence of various factors. During the interruption and the subsequent recovery, a transition from plasma to gas discharge physics occurs. Therefore, an existing test setup is extended and a measurement method is developed.

This thesis focuses on the influence of different currents and contact distances on the recovery behavior. Additionally, the impact of the commutation time from the SSD to the surge protection device (SPD) is analyzed. This is done by measuring the breakdown voltage at various times after current zero. Both the immediate recovery voltage and the recovery speed are examined. The statistical evaluation is done using linear regressions, and the results are compared with literature.

To provide an explanation for the observations, an empirical and a semi-empirical model are being developed. The empirical model is based on measurements and demonstrates the impact of the commutation time from the SSD to the SPD. The semi-empirical model is based on physical equations and experimental data. It simulates the distribution of charges of the recovering plasma column under the influence of different switch-off overvoltages. The semi-empirical model is verified through literature, measurements and the empirical model. Furthermore, recommendations for manufacturers of HSDs are derived.