Connecting networks with VSC HVDC in Africa: Caprivi Link interconnector

The Caprivi Link HVDC Scheme in Namibia connects the AC networks of Namibia and Zambia with 950km of overhead line operating at 350kV DC. Commissioning of the 300MW monopole phase of the scheme was completed in October 2010. The scheme has been designed for a future bipole extension to 600MW. The scheme connects two presently very weak AC networks where the fault levels are in the order of the rated power of the converters. The scheme utilises Voltage Source Converter (VSC) technology and is the first scheme to use VSC technology with overhead lines. The scheme has also been designed for earth return operation. This paper provides an overview of the scheme, the AC networks that it interconnects and the features of VSC technology that are particularly suited to connecting weak AC networks. The process of selecting sites for and the design of the earth electrodes is described. Initial operating experience is also presented.