Venda Nova III Dam

The project consisted of:

- Generator chamber;

- Transformer chamber;

- Sluice gate chamber;

- Hydraulic system tunnels;

- Equilibrium chimneys;

- Water inlet on the Venda Nova reservoir;

- Salamonde reservoir return;

- Temporary cofferdam;

- Power outlet tunnels;

- Access and attack tunnels;

- Support building and shut-off point;

- Accesses;

- Exterior layouts;

- Landscape recovery;

- All preparatory, accessory and complementary works in relation to the project.

Schematically, from the upper reservoir (Venda Nova) to the lower reservoir (Salamonde), the hydraulic system backup comprises of the following:

- Water inlet, consisting of a nozzle fitted with a fixed step and a structure for the housing and operation of the sluice gates at a distance of 65 m from the existing Venda Nova water inlet.

- Load tunnel, with an incline of some 13,81%, along its 2840 m extension and with a modified, circular type transversal section with a characteristic, unlined 12 m diameter.

- Upper equilibrium chimney, comprising of two vertical connection shafts between the load tunnel and the chimney shaft as such with a total height of some 400 m which is connected to the surface by means of a reservoir comprised of an expansion chamber.

- Lower equilibrium chimney, comprising of a vertical shaft with a tunnel expansion chamber.

- Return tunnel, sub horizontal with a total length of 1370m, with an intermediate low point where the evacuation installation is mounted and a final stretch with an ascending incline of 15% with a modified, unlined circular type transversal section, identical to the load tunnel.

- Return, comprising of a nozzle and an evacuation control slab on its connection with the Rabagão River, mounted some 120 m downstream from the Venda Nova II return.

- Waterproofing membrane injection, downstream from the subterranean plant at 9100m2.

- Channel excavated on the bed of the River Rabagão, intended to assure the right pump supply conditions. The thalweg for the channel was set at the 255.00 elevation, the width of 32 m at this elevation having been adopted between the new return and Venda Nova II and 35 m upstream from the latter along an extension of some 250 m.

The two generators projected for the Venda Nova III plant are reversible with a vertical axis, each one consisting of a single storey turbine pump and a directly connected synchronised alternator motor.

Taking into account the decision to split the flow (200m3/s) for two generators, unitary power was set at 373 MW at the turbine shaft outlet which, pursuant to the project criteria will correspond to an alternator motor of 418.5 MVA. The maximum installed power for the two generators is 751 MW.