Hydraulic construction focusing on hydropower stations

Hydraulic construction focusing on hydropower stations

Water conservancy engineering buildings (referred to as hydraulic buildings) are mainly used to concentrate the drop of natural water flow, form water head, and collect with the reservoir to adjust the flow of natural water flow to ensure that the water in the upstream reservoir has a high potential energy. The hydraulic structures of the hydropower station include barrages, gates, water diversion channels, pressure fore-pools, pressure water pipes and workshops, tail water channels, etc.

  1. Water blocking building

Dams are mainly dams, which are large-scale hydraulic structures used to cut off rivers, concentrate drop and water volume, and form reservoirs. Dams are the main body of water conservancy projects. Common dam types include earth dams, concrete gravity dams, arch dams and buttress dams.
1) earth dam
The earth dam is wide and thick, and is compacted by granular soil. Generally, they are made from local materials and built by hand.
The earth dam has a simple structure and does not require high geological conditions. The earth dam has the properties of being able to adapt to deformation, strong earthquake resistance, reliable operation and long service life. But earth dams require better anti-seepage facilities.

2) Concrete gravity dam
Concrete gravity dam is a large-volume water-retaining structure built with concrete and masonry. It mainly relies on its own gravity to maintain the stability of the dam body, and can withstand the horizontal thrust of the upstream surface and the gravity of the dam body itself. The dam body of the concrete gravity dam is poured with cement on the dam foundation of the rock base.
Compared with earth-rock dams, concrete gravity dams are easier to solve the problems of diversion and spillage, and also have better adaptability to climate, topography, geology and other conditions. The maintenance and repair work of the gravity dam is small, and it is a permanent water retaining structure. However, concrete gravity dams consume a lot of building materials, and when they are constructed in sections and layers, the technical requirements for joint treatment are high, and the structure is far more complicated than that of earth dams.

3) Arch dams and buttress dams
Arch dams and buttress dams are both cement and stone structures.
The upstream surface of the arch dam is arched, and the load on the upstream surface is transferred to the rock mass on both sides of the arch dam by the arch body.
The buttress dam is usually composed of multiple water-facing slopes or small arches. The junction of the slopes or small arches adopts a large and heavy buttress to bear the load from the water retaining surface, and then transmit the load to the dam foundation from the buttress.

  1. Water diversion building

The water diversion port is the water inlet that draws water for power generation from the river or reservoir, and the necessary gates, that is, the water inlet gate, are usually set up. The water diversion flow rate of hydropower plants is generally not large, and the set water inlet wheel can reduce the loss of carbon and small water head, and reduce the project cost and equipment cost. When the inlet bell mouth is wide open, the head loss at the inlet is small, but the orifice has many reinforcements, and the size of the gate will have an adverse effect on the dam structure: on the contrary, if the inlet bell mouth is opened small, it will produce the exact opposite. pros and cons issues.

The water diversion channel can be a tunnel, channel or pipeline. Its function is to transport water with a certain head and meet the water quality requirements to the hydropower plant. It is divided into two types: non-pressure water diversion and pressure water diversion.
Hydropower plants with high upstream water levels or large reservoirs often use pressure diversion methods. The water flow under pressure diversion fills the entire tunnel section, and the tunnel wall bears a large internal water pressure. Hydropower plants with low upstream water level or only small reservoirs often use pressureless water diversion. The working condition of pressureless water diversion tunnels is the same as that of open channels. Water has free water surface in the pressureless water diversion tunnels. Sandproof. Figure 1 is a schematic diagram of a pressureless tunnel diversion type hydropower plant.

Figure 1 - Schematic diagram of a pressureless tunnel diversion type hydropower plant
Figure 1 – Schematic diagram of a pressureless tunnel diversion type hydropower plant
  1. Power Plant

The power plant is the key to the hydropower station, and it is necessary to consider the layout of the hydropower station, water head, flow rate, water intake mode, unit model, number and transmission mode, terrain, geological and hydrological conditions, etc.
Water turbines, generators, switchboards and other auxiliary equipment are installed in the workshop, and these equipment shall be reasonably arranged according to the operation requirements to meet the requirements of convenient operation, sufficient lighting, good ventilation, easy maintenance, convenient work and investment saving.

According to the turbine model, the layout of the hydropower plant is divided into the following types.
(1) Horizontal shaft impact turbine plant: suitable for diversion or hybrid hydropower stations with high head and small flow. The water flows through the pressure water pipe into the turbine. The turbine and the generator are installed on the same floor, and the speed of the two is the same. If the speed of the coaxial transmission is different, the belt or gear drive is used.

(2) Horizontal-axis Francis turbine powerhouse: suitable for medium-head diversion type, post-dam type or hybrid hydropower station. It has a metal volute, and the generator is mostly a horizontal axis, which is placed on the same layer as the water turbine.
(3) Axial-flow fixed-blade turbine workshop: suitable for low-head diversion power plants. The water flow directly flows into the aqueduct from the aqueduct, and then enters the turbine room with no pressure water pipe.

(4) Vertical wheel Francis turbine workshop: suitable for medium head hydropower station. Turbine and generator are vertical shaft, coaxial transmission. The workshop is divided into generator layer and water turbine layer, mostly metal volutes.

(5) Tubular hydro-generator plant: suitable for low-head, large-flow riverbed hydropower stations.

In addition, there will be some other buildings in the hydropower station, for example, the transformer yard where transformers are installed and the switch station where high-voltage switches are installed, buildings that pass ships, trees, fish, sand, and sand washing.

Read more: How hydropower works and how hydropower plants are developed

Author: admin