Transmission Operators increasingly use direct current to guarantee that power is carried efficiently over long distances or to stabilise the grid as it is confronted with a growing supply of power from intermittent sources. Therefore they have also to implement and demonstrate power system technologies , both to exploit existing lines and to implement new ones. Circuit breakers are not necessary for point to point DC direct current transmission line connections (i.e. meshed HVDC networks that will, in the near future, require the interconnection of several points (“network architectures with power system technologies and novel network architectures. Therefore, in order to pave the way to multiple possibilities for future HVDC Circuit Breaker (DCCB) has been planned.
After defining architecture (see Fig.1) and requirements, in March 2013 a first prototype was tested at Alstom’s testing facility in Villeurbanne, France, in presence of an independent expert (medium voltage power tests including current conduction in closed state, fast current interruption, voltage withstand in open state). The best performance ever seen in a HVDC circuit breaker were achieved: in less than 2.5 milliseconds, the circuit breaker interrupted currents exceeding 3000 amperes.
Figure 1 – Direct Current Circuit Breaker (DCCB) demonstrator architecture
Tests continued until the end of 2013 as part of the TWENTIES project. On November 2013 the Alstom Grid full-scale prototype satisfactorily passed the tests of interrupt current over 5.2 kA with switching voltage peaking at more than 160 kV, which is also a new milestone worldwide.