DC vacuum circuit-breaker

The results of switching tests of a DC vacuum circuit-breaker designed for rated voltage 3.3 kV and rated current 3000A are presented. The circuit-breaker is intended for current interruption in the networks with fault currents up to 30 kA. To interrupt the direct current, the authors used a method of artificial current transition through zero in the electrical arc between the vacuum interrupter (VI) contacts by means of discharging a preliminary charged capacitor with countercurrent having the direction reverse to the one of the interrupted current. The countercurrent circuit was connected with the use of a triggered vacuum switch (TVS). The contacts in the VI were opened with an electromagnetic repulsion drive activated in the result of the preliminary charged capacitor discharge. The drive circuit was also controlled with the TVS. The contact opening time was 3 ms. The TVS switch-on time did not exceed several microseconds. Three test cycles were carried out for the cases of the current interruption in the mode similar to the normal one, in the fault current mode and in the low current mode. The tests proved that the circuit-breaker ensured safe current interruption in all those modes.