Please click on the links to see a larger view.
A diversion weir is used to extract water from the river in a reliable and controllable way so that water flowing in the channel will be regulated during high river flow and low flow conditions. It is also used to raise the water level and ensure a constant supply to the intake.
The water drawn from the river and fed to the turbine will usually carry a suspension of small particles. This sediment will be composed of hard abrasive materials such as sand which can cause expensive damage and rapid wear to turbine runners. To remove this material the water flow must be slowed down in settling basins so that the silt particles will settle on the basin floor. The deposit formed is then periodically flushed away.
The channel conducts the water from the intake to the forebay tank.
The length of the channel depends on local conditions. Most channels are excavated,
while sometimes structures like aqueducts are necessary. To reduce friction
and prevent leakages channels are often sealed with cement, clay or polythene
sheet.
The forebay tank forms the connection between the channel and the penstock. The main purpose is to allow the last particles to settle down before the water enters the penstock. Depending on its size it can also serve as a reservoir to store water. In front of the penstock a trashrack need to be installed to prevent large particles to enter the penstock.
The penstock is the pipe which conveys water under pressure from the forebay tank to the turbine. Penstock pipelines can either be surface mounted or buried underground. The decision will depend on the pipe material, the nature of the terrain and environmental considerations.
The transmission lines are used to transfer energy from the power house to the load.Overhead and underground lines are commonly used.Overhead lines are most often used because, by using air as the cable insulator, the cable is less expensive.
The power house is constructed to protect the turbine, generating unit and other equipment. A power house should be easily accesed in all sides for installation, maintenance and repair.
The tailrace is used to transmit the water from the power house back to the stream. It is usually a short, open canal. often, it is simply a ditch which is designed to ensure that erosion will not occur.
