DC power switching assembly and method

A DC power supply system, comprising:

• first and second DC power distribution bus sections and a DC power switching assembly wherein a first terminal of the assembly is electrically coupled to the first DC bus section of the power distribution bus and a second terminal is electrically coupled to the second DC bus section of the power distribution bus;
• wherein the DC power switching assembly comprises a plurality of series connected power switching units;
• each power switching unit comprising a first terminal of the unit having an electrical positive and an electrical negative pole and a second terminal of the unit having an electrical positive and an electrical negative pole and a power switching sub-unit electrically coupled between the first terminal and the second terminal to control current flow between the first terminal and the second terminal;
• wherein the first terminal and the second terminal have the same polarity of the pole, either positive or negative;
• wherein the sub-unit comprises at least one semiconductor device, which conducts in normal operation and no longer conducts in the event of a fault arising at one of the first and second terminals, a current limiter and a pair of series connected diodes in parallel with the current limiter, wherein the series connected diodes and current limiter are connected to one terminal of the semiconductor device;
• wherein the series connected diodes allow current flow to continue until the current limiter has discharged, if the semiconductor device no longer conducts;
• and
• wherein a voltage blocking capacitor is connected to the other terminal of the semiconductor device to block voltage when the semiconductor devices no longer conduct.