MCQs on Power Systems

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01․ Gross head of an hydroelectric power station is
the height of water level in the river where the storage is provided.
the difference of water level between the level in storage and tail race.
the height of water level in the river where the tail race is provided.
all of above.

The difference of water level between the level in storage and tail race is called gross head.

02․ What is the correct expression for the electrical power developed by
75 × 0.736 × WQHη.
( 75 / 0.736 ) × WQHη.
( 0.763 / 75 ) × WQHη.
( 7 / 75 ) × WQHη.

The electric power developed in a hydroelectric power station is given as,
P = WQHη × 9.81 × 10-3 KW.

03․ Hydro-graph is similar to
mass curve.
both B and C.

Hydro-graph indicates the power available from the stream at different times of the day or year. So hydro-graph is similar to the load curve used in the study of electrical power.

04․ The flow duration curve at a given head of a hydroelectric plant is used to determine
diversity factor for the plant.
total power available at the site.
total units of energy available.

Flow duration curve is very convenient from hydro-graph for determining the available power at site. If also gives the relation between flows and lengths of time during which they are available.

05․ Storage requirement can be determined from
flow duration curve.
hydro-graph.
mass Curve.
both B and C.

The amount of storage can be determined with the help of hydro-graph. But hydro-graph varies from year to year and therefore determination of storage capacity with the help of hydro-graph may lead to considerable error in some cases. So the storage capacity should be determined with the help of the mass curve.

06․ The annual depreciation of hydro power plant is about
0.5 - 1.5 %.
10 - 15 %.
15 - 20 %.
20 - 25 %.

The annual depreciation of hydro power plant is so less because of free cost fuel (water) and less maintenance of plant.

07․ The factor affecting run off are
amount of vegetation and weather condition in the catchment area.
the topography and nature of soil in the catchment area.
rain fall pattern, shape and size of catchment area.
all of above.

Run-off can be defined as that part of the precipitation which is available as the stream flow. The factor affecting run-off are rainfall patter, geology of the area, size and shape of catchment area, amount of the vegetation and the weather condition in the catchment area.

08․ If power P available from a hydroelectric plant is given by the formula P = 9.81QH, where Q is the flow rate through the turbine in l / s and H is the head in meters, then P will be unit of
W.
HP.
kJ / S.
kWh.

Q is the flow rate through the turbine in l / s or 1000 m3 / S. So P = ηQHW × 10-3 KW.

09․ Pump storage schemes are used to improve
the power factor.
the plant capacity factor as well as the load factor of the power system.
the diversity factor.

The purpose of providing storage is to make more water available during deficient flow times and thus increase the firm capacity of the power plant and also increase the energy generated. Availability of storage may render an otherwise uneconomical hydro power plant economical as increase in firm capacity. Hence the load factor is also increase.

10․ A hydro power plant of run off river type should be provided with pondage so that the
firm capacity of plant is increased.
kinetic energy of the running water is fully utilized.
pressure inside the turbine casing remains.

The usefulness of run off river power plants is increased by pondage. Pondage refers to storage at the plant which makes if possible to cope, hour to hour, with fluctuation of load through out a week or some longer period depending on the size of pondage. With enough pondage, the firm capacity of the power plant is increased.

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