Venda Nova III Dam

The project consisted of:

- Powerhouse;

- Transformer chamber;

- Gate chamber;

- Hydraulic system tunnels;

- Surge tanks;

- Water intake at the Venda Nova reservoir;

- Tailrace outlet at the Salamonde reservoir;

- Temporary cofferdams;

- Power outlet tunnels;

- Access and construction adits;

- Support building and switchyard;

- Access roads;

- Exterior arrangements;

- Landscape recovery;

- All preparatory, ancillary and complementary works related to the project.

Schematically, from the upper reservoir (Venda Nova) to the lower reservoir (Salamonde), the hydraulic circuit for the power reinforcement comprises:

- Water intake, consisting of an intake structure equipped with a fixed trash rack and a structure housing and operating the gates, located approximately 65 m from the existing Venda Nova II water intake.

- Pressure tunnel, with a gradient of approximately 13.81% throughout its entire length of 2840 m, and with a modified circular cross-section having a characteristic diameter of 12 m, unlined.

- Upper surge tank, comprising two vertical shafts connecting the pressure tunnel to the surge shaft itself, with a total height of approximately 400 m, connected to the surface through a reservoir forming an expansion chamber.

- Lower surge tank, comprising a vertical shaft provided with an expansion chamber in tunnel.

- Tailrace tunnel, sub-horizontal, with a total length of 1370 m, incorporating an intermediate low point where the dewatering facility is located, and a final section with a 15% ascending gradient, having the same unlined modified circular cross-section as the pressure tunnel.

- Tailrace outlet, comprising an outlet portal and a flow-control sill at its connection to the bed of the Rabagão River, located approximately 120 m upstream of the Venda Nova II tailrace outlet.

- Waterproofing grout curtain, upstream of the underground powerhouse, with an area of 9100 m².

- Channel excavated in the bed of the Rabagão River, designed to ensure adequate hydraulic conditions for pumping operation. The channel thalweg was set at elevation 255.00 m, with a width of 32 m at this elevation between the new tailrace outlet and that of Venda Nova II, increasing to 35 m downstream of the latter over a length of approximately 250 m.

The two generating units projected for the Venda Nova III power station are reversible vertical-axis units, each comprising a single-stage pump-turbine and a directly coupled synchronous motor-generator.

Following the decision to divide the flow rate (200 m³/s) between two generating units, the unit output was set at 373 MW at the turbine shaft, which, in accordance with the design criteria, corresponds to a 418.5 MVA motor-generator. The maximum installed capacity of the two units is 751 MW.