Protection systems for multi-terminal HVDC grids

Nowadays the protection of Voltage Sourced Converters (VSC-HVDC) is still a challenge as the high fault currents can damage seriously the converters. Nevertheless, the protection of HVDC grids is more complicated than point-to-point links, because of the specific requirements of HVDC grids. The protection system must detect and clear the faults within a demanding time. Moreover, HVDC circuit breakers are still not available, complicating the selective protection of the grid. Accordingly, since the protection of HVDC grids is so demanding, this issue is one of the biggest obstacles to develop HVDC grids. In this paper the protection system for HVDC grids is presented, including the measurement technology, fault detection and location algorithms and HVDC circuit breaker technology.