Vital HVDC link delivers clean power for South Africa and exports for Mozambique

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The nation of Mozambique is home to one of Africa’s fastest growing economies, thanks in part to a wealth of natural resources that include mineral deposits, aluminum and an abundant supply of hydropower.

The Cahora Bassa hydro plant on the Zambezi river in Tete province produces 2,075 megawatts (MW), most of which is exported to neighboring South Africa via a 1,400 kilometer (km) high-voltage DC transmission line. The Cahora Bassa reservoir is also Africa’s fourth largest artificial lake.

The HVDC transmission system is jointly owned by Hidroeléctrica de Cahora Bassa in Mozambique and Eskom in South Africa. It is made up of two parallel lines that stretch from the Songo converter station in Mozambique to the Apollo station near Johannesburg. About two thirds of the line’s total length is within Mozambique.

The Songo-Apollo HVDC link was first installed in the late 1970s, but was largely destroyed during 25 years of civil war and it stood unused for many years. Finally, a refurbishment project that included the replacement or repair of nearly all the 4,200 transmission line towers on the Mozambique side brought the system back online in 1998.

In 2006, Eskom contracted ABB to upgrade the Apollo converter station to raise the station’s capacity from 1,920 MW to 2,500 MW, and also lay the groundwork for a future upgrade to 3,960 MW. Now ABB is modernizing Apollo’s sister station in Mozambique.

The capacity of the Songo station will remain the same, but it will get new converter transformers, smoothing reactors, arresters and measuring equipment. The commissioning will be completed in two parts, with the DC equipment in the second half of 2013 and the transformers a year later. As with the Apollo upgrade, this project will enhance availability and reliability, ensuring a steady flow of power from Cahora Bassa.

While the Songo project is being executed wholly within Mozambique, it is important for both countries. South Africa has suffered for years with recurring power shortages, so the nearly 2 gigawatts of clean, reliable hydropower supplied from their neighbor to the northeast is critical. For Mozambique, the energy exports represent an important source of income as the country seeks to build its economy.

Mozambique has great potential as an energy exporter with around 12 GW of hydro capacity that could be developed. The Cahora Bassa plant is already one of the largest generation facilities in the South African power pool, and the HVDC transmission line linking it to the South African market will provide efficient transport for the plant’s output for many years to come.

Demand for energy, especially from clean sources, is increasing rapidly as African economies outpace not only global GDP growth but Asia as well. ABB estimates that investments of $14 billion by 2015 are required to sustain and expand Africa’s power grids with another $12.5 billion required for generation. The company already has over 5,000 employees in Africa with business hubs in Egypt and South Africa and a portfolio that is growing even faster than the region’s economies. Infrastructure projects like Songo will play a vital role in enabling Africa’s economic growth to continue.

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