Patent ID: 8467163

Claim:
An apparatus for protecting equipment connected to a high voltage direct current power line of a direct voltage power transmission network, said apparatus being configured to obtain said protection by having ground connecting means enabling connecting of said line to the ground, said ground connecting means comprising a current valve having at least one semiconductor device of turn-off type connected with a forward conducting direction thereof towards ground and at least one rectifying member connected in anti-parallel therewith, said apparatus further comprising a control unit configured to control said at least one semiconductor device to conduct for draining current from said line and by that protecting said equipment, wherein said ground connecting means further comprises at least one surge arrester configured to connect said current valve to said line and having a threshold voltage being at least 0.5 times the nominal voltage of said line to which the apparatus is configured to be connected, a resistor connected in parallel with said surge arrester and in series with said current valve and a second surge arrester connected in series with the surge arrester first mentioned and in parallel with said current valve and connected to ground.