±10 kV DC Vacuum Switch-Fuse Composite Apparatus for Distribution Grid

DC distribution grid is developing fast with the renewable energy industry. For the DC power grid, the DC circuit breakers protect the customers from the short circuit faults but they can't meet all the demands. For those power systems with little short fault probability, this paper provides a potential ±10kV DC composite apparatus, a DC electric fuse parallels with a vacuum switch, an external transverse magnetic field (ETMF) is generated to enlarge the vacuum arc voltage and help the current to transfer. Normally the vacuum switch conducts the rated and overload current, and the short-circuit current can be transferred by the vacuum arc to the fuse which interrupts the current. The ETMF powered by a 2 mF capacitor is more than 200 mT. The electric fuse's design process was supported by finite element simulation to ensure the fuse can interrupt a 5 kA fault current within 5 ms. The experimental results show the DC composite apparatus with a load switch can interrupt 0∼15 kA in 5ms. The interrupting process has been analyzed to understand the characteristics of the breaker, and the vacuum contacts’ erosion may cause the interrupting failure. This research enlarged the electric fuse's range of application.