# Objective Questions on Electrical Power Generation | 2

1. Pelton wheel turbine is a

In hydel power plants, Pelton wheel turbines are employed at high head. For Pelton wheel turbine the head is > 300 m. The Pelton wheel is a water impulse turbine. The Pelton wheel extracts energy from the impulse of moving water as opposed to its weight like traditional, overshot water level. For high speed, maximum power and efficiency, the turbine system is deigned such that the water-jet velocity is twice the velocity of the bucket. Pelton wheels are the preferred turbine for hydro power. When the available water source has relatively high hydraulic head at low flow rates, where pelton wheel is most efficient.

2. Which of following is a medium and low head turbines?

Francis turbines is employed at where head is 60 - 250 m. Kaplan turbines are employed at where head is < 60 m.

3. Which of the following is an impulse turbine?

In impulse turbines all available energy of water is converted into K.E.

4. Which of the following is a reaction turbines?

In reaction turbines at entrance to the runner only a part of available energy of water is converted into k.e and substantial path remains in the form of pressure energy.

5. Alternate formation and breakage of bubbles are called

Mostly cavitation takes place in reaction turbines. This will decrease the efficiency of turbines and cause severe damage of turbine.

6. Water hamming process in pen-stocks results in

Due to sudden closer of valve velocity of fluid decreases, pressure of fluid is increases. Hence some noise will produce this phenomenon is called water hammer.

7. A hydro electric generating station is supplied from a reservior of capacity 5 × 10 − 6 cubic meters at a head of 200 meters. Find the total energy available in KWh if the overall efficiency is 75 %?

Weight of water available is W = volume of water × density = 5 × 106 × 1000 = 5 × 109 = 5 × 109 × 9.81 N, electrical energy available = WH&etaoverall = 5 × 109 × 9.81 × 200 × 0.75 / ( 3600 × 1000) KWh = 2.044 × 106 KWh.

8. For harnessing low variable water heads, the suitable hydraulic turbine with high percentage of reaction and runner adjustive vanes is

Kaplan is used for run-of-river and poundage stations with heads of upto 61 m ( low head ). This type has an a axial flow rotor with variable pitch blades.

9. A hydraulic turbine having rated speed of 250 rpm is connected to a synchronous generator. In order to produce power at 50 Hz, the numbers of pole are required in the generator

We know that P = 120f / N (f = frequency, P = no. of poles, N = rated speed = 250 rpm)or, P = ( 120 × 50 ) / 250 = 24.

10. For large plants of capacity for more than 15 MW, what type of cooling is used?

Hydrogen cooling reduces windage losses, provides better cooling, reduces oxidation of insulation and also reduces fire hazards. So it is most suitable for large capacity plants.

11. How much KWh energy is produced by fission of 1 gm of uranium U235?

24000 KWh of amount of heat energy is produced by fission of 1 gm of uranium U235.

12. Among the following which is not non conventional energy?

Nuclear energy is considered as conventional energy source along with coal, oil, natural gas. Nuclear elements are the source of nuclear energy.

13. The 1st nuclear plant in world was commissioned in

The first nuclear plant in world was commissioned in U.S.S.R. in the year of 1954.

14. India's 1st nuclear plant was set up at

At Tarapur, India's first nuclear plant was established.

15. Nuclear fission means

The breaking up of nucleus of heavy atoms into nearly equal parts with release of huge amount of energy is known as nuclear fission. The release of huge amount of energy during fission is due to mass defect. This defect is converted into heat energy according to Einstein equation E = mc2.

16. Turbines specific speed (in s.i. units)
a. pelton wheel turbine g. 50 to 250
b. Kaplan turbine h. up to 50
c. Francis turbine i. 255 to 866

Specific speed of turbine is speed of a geometrically symmetrical turbine working under unit head and delivering unit break power (1 kW).

17. Solar thermal power generation can be achieved by

Under construction.

18. The function of moderator in a nuclear reactor is to

Under construction.

19. Reflector of a nuclear reactor are made up of

Under construction.

20. The conversion ratio of a breeder reactor is

Under construction.

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