A power converter includes first and second DC terminals between which the power converter is operable to generate a voltage difference. The power converter also includes a control unit that is configured to operate in a normal mode during normal operation of the power converter and in a fault mode when a fault occurs in a respective DC power transmission medium that is operatively connected in use to one of the first or second DC terminals. The control unit in the normal mode generates a normal operating voltage difference between the first and second DC terminals. The control unit in the fault mode generates a modified operating voltage difference between the first and second DC terminals while maintaining the respective voltage potential with respect to earth of the other of the first and second DC terminals. The modified operating voltage difference is lower than the normal operating voltage difference.