Kwanza Norte Province - Angola, Africa
Dar provided engineering services to support the heightening of the double-curved concrete dome Cambambe Dam from 110 to 130 metres. The project paved the way for the construction of a new 700 MW power plant and for the rehabilitation of the existing 260 MW power plant which, prior to the heightening, was operating at a reduced capacity of 180 MW. The overall net result was that the Angolan power network received a total of 780 MW of clean power from the Dam, over and above its available capacity before the project. Today, the Cambambe Dam and its associated hydroelectric facilities provide power for at least eight million people.
Due to the heavy sedimentation behind Cambambe Dam at its original height, the top level of the sediments was very close to the top level of the existing water reservoir. Therefore, it was not feasible to construct the second associated power plant (Cambambe II) with the reservoir behind the dam at its original level, since the water intake of the second power plant needed to be higher than the level of the sediments.
The Cambambe Dam Heightening project provided an additional 30 metres of clean water which guaranteed the feasibility of the construction of Cambambe II with four generators (175 MW each), collectively offering 700 MW of additional power. The same 30-metre increase also consequently allowed the existing Cambambe Power Plant, after rehabilitation and renovation, to operate at its originally designed capacity of 260 MW instead of the reduced capacity of 180 MW available prior to the heightening, a gain of 80 MW.
The scope of the project covered:
- Cambambe Dam at its new elevation along with the rehabilitated/new hydro ancillaries.
- 4 x 65 MW turbine generation units.
- 13 single-phase 11/220 kV, 24-MVA step-up transformers.
- One 220-kV switchgear bay.
- New 30 kV and 11 kV medium voltage switchgears.
- New 30/0.4 kV and 11/0.4 kV transformers.
- New controls.
- Communication and SCADA systems.
- Upgraded AC/DC auxiliary supplies.
- New emergency diesel generators.
- New lighting systems.
- New A/C, ventilation, and electro-mechanical systems.
Dar was also involved in rehabilitating damages to the dam itself. After detecting damages at the steps of the Cambambe Dam’s ski jump spillway, Dar performed a CFD study to evaluate the hydraulic performance of the structure. The spillway’s geometry was developed based on as-built drawings to simulate the existing conditions. Different scenarios were then studied, covering all of the spillway’s possible operational conditions. These scenarios included exploring high and low flows from the reservoir in addition to investigating different openings for the radial gates controlling the spillway. By doing so, Dar was able to determine the range of flows at which the free-falling impingement jet can cause damage to the spillway’s bottom steps. The study could then inform rehabilitation and mitigation measures.
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