Cahora Bassa (HVDC)

The southern line crossing through the Kruger National Park
Route of the Cahora Bassa HVDC scheme
Country	Mozambique, South Africa
Coordinates	15°36′41″S 32°44′59″E / 15.61139°S 32.74972°E / -15.61139; 32.74972 (Songo Converter Station) 25°55′11″S 28°16′34″E / 25.91972°S 28.27611°E / -25.91972; 28.27611 (Apollo Converter Station)
From	Cahora Bassa Dam, Mozambique
To	Johannesburg, South Africa
Owner	Eskom, Hidroelectrica de Cahora Bassa (HCB)
Manufacturer of substations	AEG-Telefunken, Brown Boveri Company, Siemens (original equipment); ABB Group (upgrade)
Commissioned	1977–1979
Type	overhead line
Type of current	HVDC
Total length	1,420 km (880 mi)
Power rating	1920 MW
DC Voltage	±533 kV
No. of poles	2

15°36′41″S 32°44′59″E / 15.61139°S 32.74972°E / -15.61139; 32.74972 (Songo Converter Station)

Cahora-Bassa (previously spelled Cabora Bassa) is the name for an HVDC power transmission system between the Cahora Bassa Hydroelectric Generation Station at the Cahora Bassa Dam in Mozambique, and Johannesburg, South Africa.

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 1,420 kilometres (880 mi) long powerline runs through inaccessible terrain, so it is mostly built as monopolar lines 1 kilometre (0.62 mi) apart. In case of a single line failure, transmission with reduced power is possible via the surviving pole and return through the earth.

Cahora-Bassa was out of service from 1985 to 1997 because of the Mozambican Civil War in the region. The project was beset with technological challenges, most notable of these being the adoption of solid-state rectification devices in a large-scale commercial installation. Mercury-arc valves had been the de facto standard for HVDC up to this time. Cahora Bassa was the first HVDC scheme ordered with thyristor valves, though its operation was delayed. It was also the first HVDC scheme operational in Africa, and the first anywhere in the world to operate above 500 kV. Significant commercial hurdles, culminating in hearings at an International Arbitration Tribunal seated in Lisbon, in 1988, also had to be overcome.