the system was built between 1974 and 1979 and can transmit 1920 megawatts at a voltage level of 533 kilovolts dc and 1800 amperes. thyristor valves are used, which unlike most other hvdc schemes are mounted outdoors and not in a valve hall. the valves are grouped into eight, 133 kv six-pulse bridges in series at each end. the long powerline runs through inaccessible terrain, so it is mostly built as monopolar lines apart. in case of a single line failure, transmission with reduced power is possible via the surviving pole and return through the earth.