SWISS electrical engineering multinational ABB yesterday said it had been awarded a $50m contract to repair the Mozambique side of a 1,400km high-voltage direct-current transmission line linking the Cahora Bassa hydro plant on the Zambezi River in Tete to Johannesburg.



In 2006, Eskom contracted ABB to upgrade its Apollo converter station — the Johannesburg side of the Cahora Bassa transmission line — to raise the station’s capacity from 1,920MW to 2,500MW, and also lay the groundwork for a future upgrade to 3,960MW.


Now ABB was modernising Songo, Apollo’s sister station in Mozambique, the engineering firm reported.  The high-voltage direct current transmission system is jointly owned by Hidroeléctrica de Cahora Bassa in Mozambique and Eskom in SA.  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 in Mozambique.



The Songo-Apollo high-voltage direct-current link was installed in the late 1970s, but was largely destroyed during 25 years of civil war and 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.



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 direct current equipment in the second half of next year and the transformers a year later.



As with the Apollo upgrade, this project would 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.



SA has suffered for years with recurring power shortages, so the nearly 2GW of clean, reliable hydropower supplied from its neighbour 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 about 12GW of hydro capacity that could be developed.



The Cahora Bassa plant is already one of the largest generation facilities in the Southern African Power Pool, and the transmission line linking it to the South African market will provide efficient transport for the plant’s output for many years to come.



ABB estimates that investments of $14bn by 2015 are required to sustain and expand Africa’s power grids, with $12.5bn more required for generation.  The company already has more than 5,000 employees in Africa, with business hubs in Egypt and SA 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.