A voltage source converter for high voltage DC power transmission is disclosed. According to one aspect, the voltage source converter is connectable between a DC network and another electrical network to interconnect the DC network and the other electrical network. The voltage source converter includes a converter unit configured to convert power flowing between the DC network and the other electrical network and at least one fault unit. One or more of the fault units includes at least one fault module having a voltage source that is operable, in the event of a short circuit in a DC network connected to the voltage source converter, to produce a voltage that acts to reduce current flowing through the voltage source converter and the short circuit.