MCQs on Power Systems

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01․ Location of a surge tank, in an hydro electric power station is near
tail race.

Surge tank is usually located as close to the power station as possible, preferably on ground to reduce the light of the tower. But in the case of medium and high head power plants, the surge tank is provided at the inlet of turbine. As it result the height of surge tank will become excessive. Because of the reason, the surge tanks are usually provided at the junction of the pressure tunnel and the penstock.

02․ An impulse turbine
always operates submerged.
is most suited for low head and high discharge power plants.
makes use of a draft tube.
operates by initial complete conversion to kinetic energy.

When the entire pressure of water is converted into kinetic energy in nozzle and the jet thus formed drives the wheel, the turbine is called impulse turbine.

03․ The specific speed ( NS ) of turbine is given by
N√( P ) / H1.25.
N√( P ) / H2/3.
P√( N ) / H3/2.
none of these.

If N is actual rotational speed of the turbine in rpm, P is output in metric hp and H is the effective head in meters then the specific speed ( NS ) is given by,

04․ For head and low discharge the water turbine used
Kaplan wheel.
Pelton wheel.
Francis turbine.
propeller turbine.

Pelton wheel is a type of impulse turbine and is suited high head and low flow plants.

05․ The draft tube is provided to
reduce the effect of water hammer.
raise the water surface of the stream to create an artificial head.
increase the acting head on the water wheel.
none of the above.

Without draft tube and the water discharges freely from the turbine exist, then the turbine operates under a head equal to the height of the head race water level above the runners exist. By providing draft tube, the operating head is increased by an amount equal to height of the runner outlet above the tail race.

06․ Where is the draft tube of a hydroelectric plant that is an airtight pipe located
At the beginning of the penstock.
Near the surge tank.
In between the runner exhaust and the tail race.
In between the penstock and runner.

An airtight pipe attached to the runner outlet and conducting water down from the wheel and discharging it under the surface of the water in the tail race is called draft tube.

07․ The area under a flow duration curve represents
total power available.
maximum rate of run-off during the period.
total of units of energy available.
total quantity of run-off during that period.

Flow duration curve is convenient from of hydro-graph for determining the available power at site. It gives the relation between flows and lengths of time during which they are available. So the area under a flow duration curve represents the total quantity of run-off during the period.

08․ Which turbine is ideally suited to pumped storage plants

Kaplan turbine is ideally suited pumped storage plants because its runner us capable of reverse operation as a pump.

09․ For harnessing low variable water heads, the suitable hydraulic turbine with reaction and adjustable vanes is

Kaplan turbine is a special type of propeller turbine having adjustable blades and suitable to low head and high flow plants.

10․ In kaplan runner, the number of blades is generally of the order of
1 - 2.
3 - 6.
16 - 24.
12 - 16.

The runner blade in Kaplan turbine is less than other water turbine. It is in order of 3 to 6.