The surge tank is one of the hydraulic structures in a hydro-electric power. A Surge tank is a water storage device that is used as a pressure neutralizer in hydropower water conveyance systems. Its primary purpose is to dampen excess pressure variance.
Also see: 5 Types of Electrical Equipment at Hydro Power Plants
In a hydropower plant water from water reservoir is carried to turbines using conduits. Conduits can either be open or closed. Open conduits leading water to the turbine don’t require any protection, since regulating gates control the inflow at the headworks and the spillway is used for discharging the surplus water.
However, in case of closed conduits, there exists abnormal pressure in the conduit which should be suppressed. In order to achieve this, closed conduits are always provided with a surge tank.
See the figure below:
The surge tank is located near the beginning of the conduit.
The surge tank is a small reservoir tank that is open at the top). In a surge tank, the water level rises or falls in order to suppress the pressure swings in the conduit.
Under normal load conditions, the turbine runs at a steady load and there are no surges in the flow of water through the conduit. However, in case of smaller power demand, the governor closes the gates of the turbine, thereby reducing the water supply to the turbine.
When that happens, the excess water at the lower end of the conduit rushes back to the surge tank and increases its water level. As a result, the conduit is safe and is prevented from bursting.
Now, when demand on the turbine increases, additional water is drawn from the surge tank in order to meet the increased demand.
Summarizing above, a surge tank plays two primary roles:
- In case of low power demand: It overcomes the abnormal pressure in the conduit when load on the turbine falls
- In case of increased power demand: It serves as a reservoir during increased of load on the turbine.
Also see: Power Generation MCQs