SURGE TANK
In a hydroelectric plant, the turbine drives an
alternator and therefore most revolve at a given speed, in order to ensure a
constant frequency of the alternating current if in such a scheme the water is
conveyed to the turbine through a long conduit, a very large mass of water is
content in the conduit and therefore considerable force are necessary to retard
or accelerate this mass when water requirement of the turbine change to match
the load to be fed by the alternator at any time. such variation of flow of
water in a turbine to maintain constant synchronous speed will produce a large
amount of pressure in the entire conduit system.
Hence a sudden increase in something,
often one that is relatively short-lived is known as a surge and is the simplest
means of eliminating positive( or negative) water hammer pressure by providing
a bypass to take the rejected flow. Surge tanks may be considered essentially as
a forebay close to the machine. Their primary purpose is the protection
of the long pressure tunnel in medium- and high-head plants against high water
hammer pressures caused by sudden rejection or acceptance of load. The surge tank
converts these fast (water hammer) pressure oscillations into much slower and
lower–pressure fluctuations due to mass oscillation in the surge chamber.
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