A new ultra-fast HVDC Circuit breaker for meshed DC networks

One of the major challenges of realising a Multi-Terminal DC grid has been the lack of a suitable HVDC Breaker. Previous designs of HVDC breaker were either too slow to be suitable for interrupting fast-rising fault currents or had conduction losses too high for economically viable operation on a grid. However, the new class of "hybrid" DC circuit breakers has fundamentally changed this position, with the potential of interrupting fault currents in a few milliseconds with negligible steady-state power losses. As part of the EU-funded "Twenties" project, Alstom Grid has built and tested a 120kV prototype DC breaker. The design of the breaker and the results obtained during testing are described in the paper.