Table 2: Akosombo Dam – technical data

Power house On the west bank, adjacent to the main dam is sited the six unit power house. All the six units have been recently replaced with technologically superior state-of-the-art turbine runners, increasing the installed capacity from 912MW to 1,020MW.
Spillways On the east bank of the river and also adjacent to the dam itself are twin spillways, each comprising six 11.7m by 13.8m steel gates, designed to carry away flood surplus to prevent damage to the dam. The dam’s designers made allowance in calculating the capacity of the twin spillways for the flood that could be expected.
The lake Volta lake was created as a result of the dam built at Akosombo. The 400km lake is the largest man made lake in the world in terms of surface area (8,502km2).
Generators The 11m diameter generators are wound with coils
Rating: 179.95 MVA at containing some 4.3km of copper wire. The rotor is 10.5m
14.4kV, 09 PFM in diameter and the total weight of the rotating parts, including
Manufacturer: General Electric, Canada. the shaft weigh 500 tonnes.
Penstocks The penstocks are 7.4m in diameter and 110.8m long.
Type: steel, one per unit The 4.6m-6.2m sections weigh up to 50 tonnes.
Diameter: 7.2m
Length: 112m to 116m
Turbines All six units are spun by the water falling through the
Unit output: 173.1MW penstocks. The design is such that it utilises the energy of the
(222000 hp) (retrofitted units) motive water efficiently.
Head (max): 68.88m
Synchronous speed: 115.4 rev/min
Type of turbine: Francis, Vertical shaft
Manufacturer: VA Tech, Voest Alpine, Austria.
Transformers The power at Akosombo is generated at 14.4kV and is then
Rating: 200 MVA, 14.4/161kV ideal for the purpose of transmitting the power to other areas of
Cooling: OFAF of the nation. At selected points, the high tension electricity has to
Manufacturer: be reduced to required voltage and these accounts for the series
General Electric, Canada. of sub-stations at key distribution points round the network.
Transmission Volta River Authority (VRA) operates a nationwide transmission system comprising 102km of 69kV lines, 2480km of 161kV lines and 217km of 225kV lines connecting Ghana, Togo, Benin and Ivory Coast to the national grid.