RENEWABLE ENERGY & ELECTRIFICATION
Recommissioning Unit 1 at Eskom’s Drakensberg plant
M
ar thinusen & Coutts (M&C), a division of Actom, completed a significant rewind in midNovember 2020 after being contracted by Voith Hydro, based in Germany, to wind the stator of Unit 1 at Eskom’s Drakensberg pump storage scheme. The massive stator winding contract, performed by a winding team from M&C under the supervision of Voith, was the final stage in the refurbishment of three of the station’s four 250 MW motor-generator units. Eskom engaged Voith to refurbish Unit 1. M&C has worked with Voith over several years on projects that include a stator rewind at Eskom’s Ingula pumped storage scheme. The 6.5 m diameter stator was wound in situ under Voith’s supervision after removal of the rotor. Deploying a Voith-supplied winding kit, the winding teams were required to install a total of 720 heavy-duty stator bars that had to be connected in an extremely complex bus arrangement. “Our teams had to undergo special training by Voith technicians before getting started on it,” explains Richard Botton, CEO, M&C.
30
IMIESA October 2021
Recommissioning Covid-19 travel restrictions at the time prevented Voith from flying one of its senior engineers from Germany to recommission the unit. In response, Voith requested M&C to complete this phase of the project, which was carried out by Rob Melaia, executive: Engineering & Technical, M&C. Previous power plants commissioned by Melaia as part of M&C contracts include the N’zilo hydro station in Katanga province, DRC, in 2013 and the SA Bureau of Standards’ National Electrical Test Facility’s High Power test laboratory in Gauteng last year. Senior technicians at Voith’s head office in Heidenheim, Germany, provided detailed instructions on the required procedures. “By the time I got there, I was thoroughly briefed about what I was required to do. The process was challenging, and I had to give it all my attention,” explains Melaia. “The one single thing that gave me the greatest confidence was knowing that M&C had done the winding of the stator. I wouldn’t have felt so confident if anyone else had done it.” M&C successfully performed the recommissioning of Unit 1 over a period of five days in March 2021.
DRAKENSBERG PUMPED STORAGE SCHEME Location Northern Drakensberg, KwaZuluNatal, close to the town of Bergville History Construction of the scheme started in 1974 and the last unit was put into commercial operation in 1981. A special feature of the station is that it is constructed entirely underground with only a dam wall, lift shaft buildings and transmission lines visible at the surface. The four reversible pump turbines are situated 52 storeys below ground level. Technical details - 4 x 250 MW generating sets - Installed capacity of 1 000 MW - Nominal operating head of 450 m (Source: Eskom)
