SMOOTHING REACTOR NOW IN CAHORA BASSA DISTRICT

The smoothing reactor ordered from South Africa to repair the breakdown that has severely reduced the ability of the Cahora Bassa dam to distribute electricity has now entered Cahora Bassa district, in the western Mozambican province of Tete, according to a report in Friday’s issue of the Maputo daily “Noticias”.The reactor weighs 150 tonnes and thus transporting it has been no easy task. It was driven across Zimbabwe and on Thursday was eight kilometres from the sub-station at the dam town of Songo.  The final part of the journey is over mountainous terrain. According to a source in Hidroelectrica de Cahora Bassa (HCB), the dam operating company, alterations must be made to the special truck carrying the reactor, so that it can deal with the climb and the curves on the final part of the road to Songo. If all goes well, the reactor should reach Songo on Saturday. In direct current systems, a smoothing reactor is used to “smoothen” the direct current wave shape to reduce power losses and improve system performance. In October 2010, one of the smoothing reactors at the Songo converter station suffered a major breakdown.A spare reactor was on site, but it too broke down on 24 July this year. HCB already had a plan to refurbish the converter station, but this will only begin in April 2013. Without the reactor, HCB’s capacity to send power southwards to its main client, the South African electricity company Eskom, was severely curtailed.Eskom itself had a spare smoothing reactor, and HCB negotiated for this to be sent by road to Cahora Bassa. The route was chosen to avoid taking the enormous load over many bridges. Engineering work was needed when crossing the Mazoe river, just north of the Zimbabwean border, where a provisional dike was installed.Three of the five transmission lines leaving Songo carry alternating current (taking power to northern and central Mozambique and to Zimbabwe). The other two lines carry direct current to South Africa. The direct current option was chosen because of the long distance (1,400 kilometres) from Songo to the Apollo sub-station in South Africa, The converter station changes alternating current into direct current, and it is the smoothing reactor for one of the lines to South Africa that has broken down. HCB says that because of the breakdown the company is only operating at 70 per cent of its normal capacity.