Unlike most AC circuit breakers that interrupt a fault current at a natural zero crossing, DC circuit breakers must actively force the current to zero. This is done by creating a voltage that is higher than the system voltage and absorbing the energy from the network so that the current decreases. How fast the circuit breaker needs to react and interrupt the current is mainly determined by how much over-current the system can handle, but there might also be benefits for the circuit breaker itself.
The injection type DC circuit breaker is based on injecting a current pulse through the circuit breaker, causing a zero crossing and interrupting the current. With a fast enough mechanical switch, the current can be limited and interrupted on the rising edge, reducing the requirements on the capacitors that store the energy for the injected current, and saving cost.
ABB contributes to the THEUS project through the combined expertise of its Corporate Research Center in Sweden and the ELDS division in Italy, ensuring that the project delivers innovative solutions with a clear pathway toward future product implementation and market adoption.
Within the THEUS project ABB has developed and experimentally validated a high-speed mechanical switch based on a Thomson actuated vacuum interrupter. With the fast actuator, the vacuum interrupter can obtain a large enough contact gap to perform the interruption within 400 microseconds after triggering as seen when interrupting a 400-ampere current in a 3 kV set-up.
The photo is taken in the ABB testing facilities in Västerås, Sweden during a testing session of the THEUS project. The people in the photo are: Marco Riva, Johan Nyberg, Jesper Magnusson, and Anna Huwyler.
