1. Transmission line connects
(a) generating station to a switching station/step down transformer station
(b) step down transformer station to service transformer banks
(c) Distribution transformer to consumer premises
(d) service points to consumer premises
Ans: (a) generating station to a switching station/step down transformer station
2. A 3-phase 4-wire system is commonly used for
(a) Primary distribution
(b) secondary distribution
(c) primary ditribution
(d) Secondary transmission
Ans: (b) secondary distribution
3. The rated voltage of a 3-phase power system is given as
(a) rms phase voltage
(b) peak phase voltage
(c) rms line to line voltage
(d) peak line to line voltage
Ans: (c) rms line to line voltage
4. which of the following is usually not the generating voltage
(a) 6.6 KV
(b) 9.9 KV
(c) 11 KV
(d) 13.2 KV
Ans: (b) 9.9 KV
5. In a transmission system feeder supply power to
(a) transformer substation(step-up)
(b) service mains
(c) distributors
(d) all of the above
Ans: (c) distributors
6. Feeder is designed mainly from the point of view of
(a) Its current carrying capacity
(b) voltage drop in it
(c) operating voltage
(d) operating frequency
Ans: (a) Its current carrying capacity
7. Distributors are designed mainly from the point of view of
(a) its current carrying capacity
(b) voltage drop in it
(c) operating voltage
(d) operating frequency
Ans: (b) voltage drop in it
8. Transmission and distribution of electric power by the underground system is superior to overhead system in respect of
(a) appearance and public safety
(b) maintenance cost
(c) frequency of faults, power failure, and accidents
(d) all of the above
Ans: (d) all of the above
9. For high voltage transmission lines, conductor is suspended from towers so as to
(A) Increase clearance from the ground
(B) Reduce clearance from the ground
(C) take care of the increase in length
(D) reduce wind and snow effect
Ans: (A) Increase clearance from the ground
10. The support used for transmission lines should have the characteristic(s) of
(A) High mechanical strength and longer life
(B) good looking, light in weight, and easily accessible for painting and erection of line conductors
(C) cheap in initial as well in maintenance cost
(D) all of the above
Ans: (D) all of the above
11. The wooden poles well impregnated with cerosite oil or any preservative compound have the life of
(A) 25-30 years
(B) 20-25 years
(C) 10-15 years
(D) 5-10 years
Ans: (A) 25-30 years
12. Steel pole for transmission lines need protection against
(A) borer
(B) termites
(C) corrosion
(D) all of these
Ans:(C) corrosion
13. RCC poles usually have the spans of
(A) 250-400 m
(B) 80-150 m
(C) 50-80 m
(D) 25-50 m
Ans: (B) 80-150 m
14. In India for the distribution of electric power we usually use
(A) wooden poles
(B) steel poles
(C) RCC poles
(D) both (B) and (C)
Ans: (D) both (B) and (C)
15. Conductor used in ht transmission lines are stranded because of
(A) increased tensile strength
(B) ease in handling
(C) cheaper in cost
(D) reduced resistivity
Ans: (B) ease in handling
16. Which of the following properties has got higher value for aluminium in comparison to that of copper?
(A) Electrical resistivity
(B) Thermal conductivity
(C) melting point
(D) specific gravity
Ans: (A) Electrical resistivity
17. ACSR conductor is used in place of copper in overhead lines because of
(A) higher current carrying capacity
(B) being lighter in weight
(C) economy
(D) higher tensile strength
Ans: (C) economy
18. ACSR conductors have
(A) All conductor made of aluminium
(B) the outer conductor made of aluminium
(C) inner conductor made of aluminium
(D) no conductor made of aluminium
Ans: (B) the outer conductor made of aluminium
19. Function of steel wire in an ACSR conductor is to
(A) compensate for skin effect
(B) Take care of surges
(C) provide addition mechanical strength
(D) Reduce inductance
Ans: (C) provide additional mechanical strength
20. The material used for the manufacture of the ground wire is
(A) aluminium
(B) galvanized steel
(C) cast iron
(D) stainess steel
Ans: (B) galvanized steel
21. Guy wire is employed for
(A) providing protection against surges
(B) providing emergency earth route
(C) supporting the pole
(D) all of the above
Ans: (C) supporting the pole
22. The sag of a transmission line is least affected owing to
(A) Weight of the conductor
(B) current through the conductor
(C) atmospheric temperature
(D) ice deposition on the conductor
Ans: (B) current through the conductor
23. Effect of temperature rise in overhead lines is to
(A) Increase the sag and decrease the tention
(B) Decrease the sag and increase the tention
(C) increase both
(D) decrease both
Ans: (A) Increase the sag and decrease the tention
24. The sag of a transmission line conductor in summer is
(A) less than that in winter
(B) more than that in winter
(C) same as in winter
(D) none of above
Ans: (B) more than that in winter
25. In a transmission line sag depends upon
(A) span length
(B) tention in conductor
(C) weight of the conductor per unit length
(D) all of the above
Ans: (D) all of the above
26. Which of the following statement is correct ?
(A) Ice on the conductor increase the skin effect
(B) wind pressure reduce the coron effect
(C) wind pressure taken to act at perpendicular to that foe ice
(D) ice on the conducor reduce the sag
Ans: (C) wind pressure taken to act at perpendicular to that foe ice
27. Wind loading in coastal regions is in the range of
(A) 40 - 50 kg/m2
(B) 150 kg/m2
(C) 96 kg/m2
(D) 120 kg/m2
Ans: (B) 150 kg/m2
28. Strain type insulators are used
(A) at dead ends
(B) at intermediate anchoe towers
(C) on straight runs
(D) any of (A) or (B)
Ans:(D) any of (A) or (B)
29. For 400 Kv line, the spacing between phase conductors is around
(A) 8 m
(B) 11 m
(C) 14 m
(D) 17 m
Ans: (A) 8 m
30. wavy structure of pin insulator increase its
(A) mechanical strength
(B) puncture strength
(C) flash over voltage
(D) thermal strength
Ans: (C) flash over voltage
31. Which type of insulators are used on 132Kv transmission lines ?
(A) pin type
(B) disc type
(C) shackle type
(D) pin and shackle type
Ans: (B) disc type
32. Whenever the condcutor are dead ended or there is a change in the direction of transmission line, the insualtors used are of the
(A) Pin type
(B) suspension type
(C) strain type
(D) shackle type
Ans: (C) strain type
33. Post type insulators are generally used in line operating
(A) above 100 kv
(B) below 33 kv
(C) at any voltage level Hv or ehv
(D) none of the above
Ans: (C) at any voltage level Hv or ehv
34. The number of discs in a string of insulators for 400kv ac overhead transmission line lies in the range of
(A) 32 to 33
(B) 22 to 23
(C) 15 to 16
(D) 9 t0 10
Ans: (B) 22 to 23
35. The voltages across the various disc of a string of suspension insulators having identical discs is different due to
(A) Surface leakage current
(B) series capacitance
(C) shunt capacitance to ground
(D) series and shunt capacitances
Ans: (C) shunt capacitance to ground
36. The string efficiency of a string of suspension insulators is dependent on
(A) size of the insulators
(B) number of the disc in the string
(C) size of tower
(D) none of the above
Ans:(B) number of the disc in the string
37. 100 per cent string efficiency means
(A) one of the insulator discs shorted
(B) zero potential across each disc
(C) equal potential across each insulator disc
(D) none of the above
Ans: (C) equal potential across each insulator disc
38. In a suspension type insulator the potential drop is
(A) maximum across the lowest disc
(B) maximum across the topmost disc
(C) uniformly distributed over the disc
(D) None of the above
Ans: (A) maximum across the lowest disc
39. The string efficiency of a high voltage line around
(A) 100 %
(B) 80 %
(C) 40 %
(D) 10 %
Ans: (B) 80 %
40. The insulators may fail due to
(A) flash over
(B) short circuit
(C) deposition of dust
(D) any of the above
Ans: (D) any of the above
41. The ratio of puncture voltage to the flash overvoltages of a line insulator is
(A) equal to 1
(B) lower than 1
(C) much greater than 1
(D) none of the above
Ans: (C) much greater than 1
42. The purpose of guard ring in transmission line is to
(A) reduce the earth capacitance of the lowest unit
(B) increase the earth capacitance of the lowest unit
(C) reduce the transmission line losses
(D) none of the above
Ans: (A) reduce the earth capacitance of the lowest unit
43. The use of a guard ring
(A) equalize the voltage division between insulators disc
(B) is unnecessary complication
(C) decrease the string efficency
(D) none of the above
Ans: (A) equalize the voltage division between insulators disc
44. Coron is
(A) partial breakdown of air
(B) complete breakdown of air
(C) sparking between lines
(D) none of the above
Ans: (A) partial breakdown of air
45. coron is accompanied by
(A) violer visible dicharge in darkness
(B) hissing sound
(C) vibration
(D) radio interference
(E) ozone
(F) all of the above
Ans: (F) all of the above
46. ozone effect can be detected by
(A) presence of ozone detected by odour
(B) hissing sound
(C) faint luminous glow of bluish colour
(D) all of the above
Ans: (D) all of the above
47. Corona loss increases with
(A) decrease in conductor size and increase in supply frequency
(B) increase in both conductor size and supply frequency
(C) decrease in both conductor size and supply frequency
(D) Increase in conductor size and decrease in supply frequency
Ans: (A) decrease in conductor size and increase in supply frequency
48.The chances of occurrence of corona are maximum during
(A) humid weather
(B) dry weather
(C) winter
(D) hot summer
Ans: (A) humid weather
49. coron is likely to occure maximum in case of
(A) distribution lines
(B) transmission lines
(C) domestic wiring
(D) service mains
Ans: (B) transmission lines
50. Corona is affected by
(A) size of conductor
(B) shape and surface condition of the conductor
(C) operating Voltage
(D) all of the above
Ans: (D) all of the above
