Connection with Hydro Electric Power Station
Q. Explain the following terms in connection with hydro-electric power station :
- Tunnel
- Surge tank
- Reservoir
- Tall race
- Tunnel : Tunnels are underground passageways commonly in rock used to carry water for power between two points. A typical arrangement is to convey water for power in a tunnel at low head, followed by a transition to a steep penstock to the powerhouse, with surge handled in a surge tank at the transition. A tunnel can be pressurized or unpressurized. Unpressurized tunnel flow is similar to open channel flow. By using pressure tunnel, the water passes from the reservoir to the surge tank.
- Surge tank : This is a tank provided near the turbine. As the load on the turbine decreases suddenly, water flow to the turbine reduces suddenly. This causes a hammer effect on the penstock. This effect is absorbed by the surge tank by providing space for the additional water.
- Reservoir : Continuous availability of water is the basic necessity for a hydro-electric plant. Water collected from catchment area during rainy season is stored in the reservoir. Water surface in the storage reservoir is known as head race.
- Tall race : The tail race is a water way to lead water discharged from the turbine to the river. Water level of the tail race should be kept high enough so as to avoid cavitation near the runners when the Francis or Kaplan turbines are used.