This scheme, equipped from the outset with valves provided by Swedish subcontractor, was designed to transmit 560 megawatts, in the first phase, at a symmetrical bipolar voltage of ±500 kilovolts. Although not the first 500 kV HVDC project in operation (the ±533 kV scheme having been completed in 1977) it was the first such scheme to use only a single per pole.