Patent ID: 8830636

Claim:
A high voltage DC switchyard comprising: at least one busbar, at least two DC lines each connected to said at least one busbar through DC breakers comprising a section of at least one semiconductor device of turn-off type and a rectifying member connected in anti-parallel therewith, means configured to detect occurrence of a fault current in connection with said busbar or DC lines, and a control unit configured to control said DC breakers for protecting equipment connected to said busbar and/or DC lines upon occurrence of a said fault current, wherein at least one said DC line is connected to at least one said busbar through a unidirectional said DC breaker, said DC switchyard has two busbars and being a one and half breaker switchyard having three said DC breakers per two said DC lines, a first DC breaker connecting a first of the DC lines to a first of said busbars, a second DC breaker connecting a second of the DC lines to a second of said busbars and a third DC breaker in a current path interconnecting the first and second DC breakers, where the first and second DC breakers are said unidirectional DC breakers and said third DC breaker is a bidirectional DC breaker having at least two sections connected in series and with semiconductor devices thereof with opposite conducting directions, wherein said first and second DC breakers have the semiconductor devices thereof directed to conduct in the direction towards the first and second busbar, respectively, and that said control unit is configured to control said first or second DC breaker to open for disconnecting the respective DC line from the respective busbar in the case of occurrence of a fault of that busbar, or said DC breakers connecting the DC lines to a said busbar have their semiconductor devices directed to conduct away from said busbar, respectively, and that said control unit is configured to control these DC breakers to open for disconnecting said busbar in the case of a fault of a line connected to that busbar through this DC breaker.