POWER SYSTEMS 1

POWER  SYSTEMS

11. In thermal power plants, the pressure in the working fluid cycle is developed by
a) Condenser
b) Superheater
c) feed water
d) turbine
ans: d

12. Which material is used in controlling chain reaction in av nuclear reactor?
a) Thorium
b) Heavy water
c) Boron
d) Beryllium
ans: b

13. When a fixed amount of power is transmitted, the efficiency of transmission increases when
a) Voltage decreases, power factor remains constant
b) voltage increases, power factor increase
c) voltage decreases, power factor decreases
d) voltage constant, power factor decreases
ans: b

14. The surge impedance of 0.400km long OH line is 400 ohm for 200 km length of the same line, the surge impedance will be
a) 200 ohm
b) 800 ohm
c) 400 ohm
d) 100 ohm
ans: c

15. The insulation level of a 400 EHV OH transmission line is decided on the basis of
a) lightning voltage
b) switching overvoltage
c) corona inception voltage
d) radio and TV interference
ans: b

16. Bundled conductors are employed to improve the
a) appearance of the transmission line
b) mechanical stability of the line
c) decrease system stability
d) increase the short circuit current
ans: c

17. An OH line having a surge impedance of 400 ohms is connected in series with an underground cable having a surge impedance of 100 ohm. If a surge of 50 Kv travels from the line end towards the line cable junctions, the value of the transmitted voltage wave at the junction is
a) 30 kV
b) 20 kV
c) 80 kV
d) -30 Kv
ans: b

19. The load-carrying capability of a long AC transmission line is
a) always limited by the conductor size
b) limited by stability considerations
c) reduced at low ambient temperatures
d) decreased by the use of bundled conductors of single conductors.
ans: b

20. Corona losses are minimized when
a) corona size is reduced
b) smooth conductor is released
c) sharp points are provided in the hardware
d) current density in conductors is reduced
ans: b

POWER SYSTEMS 2

POWER  SYSTEMS

21. The corona loss on a particular system at 50HZ is 1kw/km/ph. The corona loss at 60 HZ is
a) 1kw/ph/km
b) 0-83 kw/km/ph
c) 1.2 kw/km/ph
d) 1.13 kw/km/ph
ans: d

22. A loss-less radial transmission line with surge impedance loading
a) takes negative VAR at sending end and zero VAR at receiving end
b) take positive VAR at sending end and zero VAR at receiving end
c) has flat voltage profile and unity power factor at all points along with it
d) has sending end voltage higher than receiving end voltage and unity power factor at sending end
ans: c

23. Consider along, two wirelines composed of solid round conductors. The radius of both conductors is 0.25 cm and the distance between their centers is 1m. If this distance is doubled, then the inductance per unit length
a) doubles
b) halves
c) increase but does not double
d) decreases but not halve
ans: c

24. A long wire composed of a smooth round conductor runs above and parallel to the ground. A high voltage exists between the conductor and the ground. The max electric stress occurs at.
a) the upper surface of the conductor
b) the lower surface of the conductor
c) the ground surface
d) none of the above
ans: b

25. Bundled conductors are mainly used in high voltage OH transmission lines to
a) reduce transmission line losses
b) increase the mechanical strength of the line
c) reduce corona
d) reduce sag
ans: c

POWER SYSTEMS

1. For low head and high discharge the hydraulic turbine used is
a) Francis turbine
b) Kaplan turbine
c) Pelton wheel
d) none of the above
ans: b

2. A Kaplan turbine is
a) In ward flow, impulse turbine
b) Outward flow reaction turbine
c) A high head mixed flow turbine
d) Low head axial flow turbine
ans: d

3. An hydro-graph indicates
a) The discharge at any time during the period under consideration
b) The max. and min. runoff during the period
c) The average run off during the period
d) all the above
ans: d

4. As compared to steam-station ,hydro-electric stations have :
a) More cost of installation
b) Less maintenance and fuel cost
c) both (a) and (b)
d) Low depreciation charges.
ans: c

5. The rotor used in alternators of hydro-electric station is
a) Cylindrical rotor
b) Salient pole rotor
c) Non salient pole rotor
d) Round rotor with ac excitation
ans: b

6. The cost of fuel transportation is minimum in ______ plant.
a) Thermal
b) Nuclear
c) Hydro
d) Diesel
ans: c

7. Which of the following generating stations has minimum running cost.
a) Thermal
b) Nuclear
c) Hydro
d) none of these
ans: c

8. Which of the following plants have the highest capital cost
a) Nuclear
b) Diesel
c) Thermal
d) none
ans: a

9. For harnessing low variable water heads, the suitable hydraulic turbine with high percentage of reaction and runner adjustable vanes is
a) Kaplan
b) Francis
c) Pelton
d) Impeller
ans: a

10. In a Thermal power plant, the feed water coming to the economizer is heated using
a) H.P. steam
b) L.P. steam
c) direct heat in the furnace
d) flue gases
ans: d