A DC power supply system has first and second DC power distribution bus sections and a DC power switching assembly has a plurality of series connected power switching units and a current limiter. Each power switching unit has a first and second power switching unit terminal and two symmetrical power switching sub-units to control current flow between. Each sub-unit is electrically connected on one side to one of the first and second power switching unit terminals and on the other side to the other sub-unit. The power switching sub-units each have a semiconductor device and in parallel with the semiconductor device, a series connected diode and capacitor. A first terminal of the assembly is electrically coupled to the first bus section and the second terminal is electrically coupled to the second bus section. The voltage at one side of the power switching assembly is greater than or equal to 1 kV.