Patent ID: 8817427

Claim:
A current-limitation system for limiting a current through a DC connection in case of a fault occurring in a DC grid of which the DC connection forms a part, the current-limitation system comprising a current limiter for series-connection into the DC connection, and a control system for controlling the current-limiting strength of the current limiter; wherein the current limiter comprises a series connection of independently controllable breaker sections, wherein a breaker section comprises a parallel connection of a non-linear resistor and a semi-conductor switch of turn-off type; the control system comprises a current measuring device; and the control system is operable to: detect a fault; and, in response to detecting the fault, adjust the current-limiting strength of the current limiter, the current-limitation system being wherein the control system further comprises a voltage measuring device arranged to measure the voltage at at least one side of the current limiter; the control system is operable to detect a fault by checking whether the voltage at at least one side of the current limiter has fallen below a first voltage threshold; the current measuring device is arranged to measure the current through the current limiter; and the control system is operable to adjust, in response to detection of a fault, the current-limiting strength of a current limiter in a manner so that if the current through the current limiter exceeds a first current threshold (I max ), the current-limiting strength is increased; and if the current through the current limiter falls below a second current threshold level (I min ), the current-limiting strength is decreased, wherein the first current threshold lies below the rated current of the transmission.