Overview about different 500 V low voltage DC-Switchgear topologies and comparison of their switch off performance

Abstract:
This publication presents results of the research project Smart Modular Switchgear-II (SMS II). SMS-II includes three topics, DC-Grids, an automated protection routine and DC-Switchgear. Part of the project is the development of DC-Switchgear for the 1 kV and 3 kV voltage level. The focus of the current publication is the determination of the optimal switching device for a DC model network with three voltage levels (0,38 kV, 1 kV and 3 kV). Therefore, the requirements of DC-Grids on DC-Switchgear are defined. The different control modes of power electronic sources and converters are taken into consideration. The test values are therefore limited to the partial load range and nominal range. The requirements are applied to the performance data of the different switchgear types, which are extracted from the literature. The result is the hypothesis, that the hybrid switch is the most suitable type of DC-Switchgear for the proposed application. The hypothesis is verified by basic experimental investigations in the DC Laboratory of the TU Braunschweig under 450 V. Subjects of the investigations are two mechanical contactors and a hybrid switch. The mechanical contactors differ regarding their extinguishing method. The analysis of the investigation results of the switch off performance confirm the proposed hypothesis. For example, the hybrid switch shows the fastest switch off time and lowest arc energy over all investigated test currents and time constants. Further on, the switch off time of the mechanical switchgear is analysed under different load conditions. The switch off time is divided in two sections. The defined sections enable to explain the progression of the switch off time. The partial results must be further investigated in the future.