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# Power Systems (Transmissions & Distribution) Expected MCQ PDF 2 For VIZAG MT Exam 2017

1)   In which climate does the chances of occurrence of corona is maximum?
a. Dry
b. Hot summer
c. Winter
d. Humid

2)   Corona loss can be reduced by using
1. Solid conductor.
2. Hollow conductor.
3. Bundle conductor.
a. 1 only
b. 1 and 2 only
c. 1, 2 and 3 only
d. 2 and 3 only

3)   What is the effect on corona, if the spacing between the conductors is increased?
a. Corona increases
b. Corona is absent
c. Corona decreases
d. None of these

4)   Why are the hollow conductors used?
a. Reduce the weight of copper
b. Improve stability
c. Reduce corona
d. Increase power transmission capacity

5)   Which of these given statements is wrong in consideration with bundled conductors?
b. Reduction in corona loss
c. Reduction in the radio interference
d. Increase in interference with communication lines

 ANSWER: Increase in interference with communication lines
6)   Why are bundled conductors employed?
a. Appearance of the transmission line is improved
b. Mechanical stability of the line is improved
c. Improves current carrying capacity
d. Improves the corona performance of the line

 ANSWER: Improves the corona performance of the line
7)   The effect of
dirt on the surface of the conductor is to _____________ irregularity
and thereby ________________ the break down voltage.

a. Decreases, reduces
b. Increases, increases
c. Increases, reduces
d. Decreases, increases

8)   Which tests are conducted to locate the fault location in the cables?
a. Murray loop test
b. Varley loop test
c. Both (a) and (b)
d. None of these

9)   Find the
spacing between the conductors a 132 kV 3 phase line with 1.956 cm
diameter conductors is built so that corona takes place, if the line
voltage exceeds 210 kV (rms). With go = 30 kV/cm.

a. 1.213 m.
b. 2.315 m.
c. 3.451 m.
d. 4.256 m.

10)   On what factor does the skin effect depend?
a. Cross section of the conductors
b. Supply frequency
c. Permeability of the conductor
d. All of these

11)   What are the line constants in a transmission line?
a. Resistance and series conductance only
b. Series and shunt conductance
c. Resistance, inductance and capacitance
d. Resistance, inductance, capacitance and shunt conductance

 ANSWER: Resistance, inductance, capacitance and shunt conductance
12)   What is the cause of skin effect?
a. Supply frequency
b. Self inductance of conductor
c. High sensitive material in the centre
d. Both (a) and (b)

13)   The
conductor carries more current on the surface in comparison to its core.
What is this phenomenon called?

a. Corona
b. Ferranti effect
c. Skin effect
d. Proximity effect

14)   By using which conductor is the skin effect reduced?
a. Bundled conductors
b. Stranded conductors
c. Hollow conductors
d. Solid conductors

15)   In which of the transmission systems is the skin effect observed?
a. Cable carrying dc current
b. DC transmission line only
c. AC transmission line only
d. DC as well as AC transmission lines

16)   Skin effect in a conductor is proportional to
a. (Diameter of conductor)1/2
b. Diameter of conductor
c. (Diameter of conductor)2
d. (Diameter of conductor)4

17)   Skin effect is negligible for what supply frequency and for what diameter?
a. < 50 Hz and < 1 cm
b. < 50 Hz and > 1 cm
c. > 50 Hz and < 1 cm
d. > 50 Hz and > 1 cm

 ANSWER: < 50 Hz and < 1 cm
18)   The current distribution may not be uniform in a conductor, which effect is this?
a. Skin effect
b. Proximity effect
c. Ferranti effect
d. None of these

19)   Proximity effect is due to the current flowing in the ___________.
a. Earth
b. Sheath
c. Nearby conductors
d. All of these

20)   Proximity effect
a. Is more in large conductors, high frequency
b. Increases the resistance of the conductor
c. Reduces the self reactance
d. All of these

21)   What is the total resistance in a single phase or 2 – wire dc line?
a. Equal to the resistance of either conductor
b. Double the resistance of either conductor
c. Half of the resistance of either conductor
d. None of these

 ANSWER: Double the resistance of either conductor
22)   The inductance of a single phase two wire power transmission line per km gets doubled when
a. Distance between the wires is doubled
b. Distance between the wires increased fourfold
c. Distance between the wires is increased as the square of the original distance
d. Radius of the wire is doubled

 ANSWER: Distance between the wires is increased as the square of the original distance
23)   The inductance of a power transmission line increases with
a. Decrease in line length
b. Increase in diameter of conductor
c. Increasing in spacing between the phase conductors
d. Increase in load current carried by the conductors

 ANSWER: Increasing in spacing between the phase conductors
24)   Inductance
of a single phase two parallel wire transmission line having conductor
radius r and spacing D between conductors is equal to

a. 2 π * 10-7ln D / r
b. 4 * 10-7ln D / r
c. 4 π * 10-7ln D / r
d. 2 * 10-7ln D / r

 ANSWER: 4 * 10-7ln D / r
25)   For a single
phase overhead line having solid copper conductors of diameter 1 cm
spaced 90 cm between the centres, the inductance in mH/km is

a. 0.05 + 0.2 ln 90
b. 0.2 ln 90
c. 0.05 + 0.2 ln (90/0.5)
d. 0.2 ln (90/0.5)

 ANSWER: 0.05 + 0.2 ln (90/0.5)
26)   The
conductor of a 15 km long, single phase two wire line are separated by a
distance of 1.5 m. The diameter of each conductor is 1 cm. If the
conductors are of copper, the inductance of the circuit is

a. 23.81 mH
b. 35.72 mH
c. 32.81 mH
d. 53.72 mH

27)   The inductance of a transmission line is minimum when_____________
a. GMD is high
b. GMR is high
c. Both GMD and GMR are high
d. GMD is low and GMR is high

 ANSWER: GMD is low and GMR is high
28)   A single
phase line has two parallel conductors 2 metre apart. The diameter of
each conductor is 1.2 cm. What is the loop inductance per km of the
line?

a. 2.423 mH
b. 1.234 mH
c. 3.267 mH
d. 8.632 mH

29)   Why is the transmission lines transposed?
a. Reduce corona loss
b. Reduce skin effect
c. Prevent interference with the neighbouring telephone lines
d. Prevent short circuit between any two lines

 ANSWER: Prevent interference with the neighborliness telephone lines
30)   A three
phase, 50Hz transmission line consists of three equal conductors of
radii ‘r’ placed in a horizontal plane with a spacing of 6m between
middle and outer conductor. If the radius of each conductor is 12.5 mm,
then inductance per phase per km of the transposed line will be

a. 1.33 mH/km
b. 1.65 mH/km
c. 0.38 mH/km
d. 2.145 mH/km

31)   A three
phase transmission line has its conductors at the corners of an
equilateral triangle with sides 3m. The diameter of each conductor is
1.63 cm. What is the inductance of the line per phase?

a. 1.232 mH
b. 1.184 mH
c. 2.236 mH
d. 2.68 mH

32)   What will be
the inductance of each conductor in a three phase, 3 wire system when
they are arranged in a horizontal plane with spacing such that D31= 4m,
D12 = D23 = 2m. The conductors are transposed and have a diameter of 2.5
cm.

a. 2.22 mH
b. 1.11 mH
c. 3.33 mH
d. 4.44 mH

33)   What is the
inductance per phase per km of a double circuit 3 phase line as shown in
the fig. The conductors are transposed and are of radius 0.75 cm each.

a. 0.725 mH
b. 0.835 mH
c. 0.623 mH
d. 0.231 mH

34)   Why is high voltage transmission lines transposed?
a. Corona losses can be minimised
b. Computation of inductance becomes easier
c. Voltage drops in the lines can be minimised
d. Phase voltage imbalances can be minimised

 ANSWER: Phase voltage imbalances can be minimised
35)   The three
phase line consists of three conductors each of diameter 21 mm. The
spacing is shown in fig. Find the inductance per phase / km.

a. 8.2 * 10-4 H / km
b. 12.22 * 10-4 H / km
c. 5.6 * 10-4 H / km
d. None of these

 ANSWER: 12.22 * 10-4 H / km
36)   When is the transposition of conductors in a transmission line done?
a. When the conductors are not equally spaced
b. When the conductors are spaced equilaterally
c. When a telephone line runs parallel to the power line
d. None of these

 ANSWER: When the conductors are not equally spaced
37)   Assertion (A): Transposition of conductors in a transmission line is necessary.
Reason (R): Corona losses are reduced by transposition of conductors.

a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true and R is not the explanation of A
c. A is true but R is false
d. A is false but R is true

 ANSWER: A is true but R is false
38)   Assertion (A): the concept of GMD is applicable for the calculation of inductance of transmission lines.
Reason
(R): The radius of the conductor of transmission lines, in the
expression for inductance is not the self GMD of the conductor.

a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true and R is not the explanation of A
c. A is true but R is false
d. A is false but R is true

 ANSWER: Both A and R are true and R is not the explanation of A
39)   In case of stranded conductors, what is the ratio of the GMR to the actual radius?
a. Equal to 1
b. More than 1
c. Equal to 0.7788
d. Less than 0.7788

40)   Ds
is the GMR of each subconductor of a four subconductor bundled
conductor and d is the bundle spacing. What is the GMR of the equivalent
single conductor?

a. 1.09 √ (Ds * d3)
b. 1.09 √ (Ds3 * d3)
c. 1.09 (√ (Ds 3 * d3))1/4
d. 1.09 (√(Ds * d3))1/4