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Friday, 2 September 2016

Electrical Supply System - Multiple Choice Questions

Electrical Supply System - Multiple Choice Questions Points : Electrical supply system multiple choice questions and answers, electrical objective type question answers, mcqs 1. If voltage is increased by n times, the size of the conductor would
(i) increase by n times
(ii) reduce by 1/n times
(iii) increase by n2 times
(iv) reduce by 1/n2

2. As a matter of economy, voltage for power transmission should be
(i) low
(ii) medium
(iii) high
(iv) none of above

3. In a supply system, the cost of conductor is
(i) directly proportional to area of cross-section
(ii) inversely proportional to area of cross-section
(iii) directly proportional to square of area of cross-section
(iv) none of above

4. The primary distribution of electric power is done by
(i) 3-phase, 4-wire system
(ii) 3-phase, 3-wire system
(iii) 1-phase system
(iv) none of above

5. The economic size of a conductor is determined by
(i) Ohm’s law
(ii) Kelvin’s law
(iii) Kirchhoff’s law
(iv) none of above

6. In a 3-phase, 4-wire a.c. system, the number of voltages we get is
(i) two
(ii) three
(iii) four
(iv) none of above

7. The term service mains refers to
(i) primary transmission
(ii) secondary transmission
(iii) primary distribution
(iv) secondary distribution

8. When transmission voltage is increased, the line losses are
(i) decreased
(ii) increased
(iii) same
(iv) none of above

9. In a 3-wire balanced d.c. system, the voltage between outer conductor and neutral is V. The voltage between the outers is
(i) V
(ii) 3V
(iii) V/2
(iv) 2V

10. In India, the transmission of electric power is done by
(i) 3-phase, 3-wire system
(ii) 3-phase, 4-wire system
(iii) 1-phase system
(iv) none of above

11. As a rough guide, the most economical transmission voltage is ……..... of the length of the line.
(i) 2 kV/cm
(ii) 1.6 kV/km
(iii) 3.2 kV/cm
(iv) 3 kV/km

12. What is the percentage saving in the conductor material used for a transmission line if, for the same power transmitted, power factor and power loss, in the line, the transmission voltage is increased from 66 kV to 132kV?
(i) 50%
(ii) 40%
(iii) 75%
(iv) 60%

13. By extra high voltage (EHV) we mean voltage
(i) 66kV
(ii) 100kV
(iii) 33 kV
(iv) above 220 kV

14. If the length of the transmission line is 300 to 400 km. the suitable transmission voltage would be
(i) 11 kV
(ii) 33kV
(iii) 66 kV
(iv) 400 kV

15. In India, secondary distribution is carried out at
(i) 4001230 V
(ii) 600/300 V
(iii) 700/350 V
(iv) none of above

16. The cost of transmission line conductor at 132 kV is Rs 100 per metre. When transmission voltage is increased to-220 kV, the cost of conductor is
(i) R.s. 36/m
(ii) Rs. 55/m
(iii) Rs. 26/m
(iv) Rs. 80.m

17. The electric power is not transmitted by dc because
(i) there is skin effect in d.c.
(ii) there is greater voltage drop
(iii) d.c. voltage cannot be stepped up
(iv) none of above

18. The cost of transmission line conductor at 110 kV is Rs. 100 per metre. At 200 kV, the cost per metre will be
(i) Rs.100
(iii) Rs. 200
(iv) Rs. 25

19. Power P is to be transmitted by overhead lines over length I. For the same power loss and the sane voltage between conductor and earth, the least conductor material required is in
(i) 2-wire d.c. system
(ii) 1-pbase a.c. system
(iii) 3-phase, 3-wire a.c. system
(iv) 3-phase, 4-wire a.c. system

20. 220 kV transmission line voltage is economical for a distance of
(i) 22km
(ii) 100 km
(iii) 200 km
(iv) 400 km

21. In a transmission line, the major cost is due to
(i) insulators
(ii) conductors
(iii) towers
(iv) none of above

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