Power Systems Transmissions 5
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Attempt Free Power Systems Transmissions 5 Here. Read The Important Electrical MCQ From Below.
1) The generating voltage and frequency in India is about?
a. 11 kV and 60 Hz
b. 11 kV and 50 Hz
c. 220 kV and 60 Hz
d. 220 kV and 50 Hz
ANSWER: 11 kV and 50 Hz
2) Which type of system is generally adopted for the generation and transmission of electrical power?
a. 3 phase 4 wire
b. 2 phase 3 wire
c. 3 phase 3 wire
d. None of these
ANSWER: 3 phase 3 wire
3) The rated voltage of a 3 phase power system is given by ____________.
a. rms peak voltage
b. Peak phase voltage
c. rms line to line voltage
d. Peak line to line voltage
ANSWER: rms line to line voltage
4) Which of these systems uses the 3 phase 4 wire system?
a. Primary distribution
b. Secondary distribution
c. Primary transmission
d. Secondary transmission
ANSWER: Secondary distribution
Power Systems Transmissions 5
5) With the same maximum voltage to earth, which among the following AC systems with 0.8 pf will need more copper compared to 2 wire system?
a. Single phase, 2 wire
b. Single phase, 3 wire
c. Three phase, 3 wire
d. Three phase, 4 wire
ANSWER: Three phase, 4 wire
6) Assertion (A): 3 wire dc distribution system is preferred over 2 wire dc distribution system.
Reason (R): the 3 wire dc system of distribution is more safe.
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
7) Assertion (A): Transmission of electrical power by dc is economical than that with ac.
Reason (R): In case of dc transmission, there is no charging current which contributes to the continuous load, even on no load.
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
Power Systems Transmissions 5
8) In transmission system, the weight of copper used is proportional to
a. Square of voltage
b. Voltage
c. 1 / (square of voltage)
d. 1 / voltage
ANSWER: 1 / (square of voltage)
9) Greater the power factor the ________________ is the volume of copper required.
a. Greater
b. Smaller
c. Both are equal
d. Depending of the level of transmission
ANSWER: Smaller
10) Line efficiency increases for ________ transmission voltages.
a. Higher
b. Lower
c. Both (a) and (b)
d. None of these
ANSWER: Higher
11) The most important disadvantage of using the high voltage for transmission is
a. The increased cost of insulating the conductors.
b. The increased cost of transformers, switchgear and the other terminal apparatus.
c. Both (a) and (b)
d. There is a reduction in the corona loss.
ANSWER: Both (a) and (b)
Power Systems Transmissions 5
12) The most suitable practical value of primary distribution is?
a. 66 kV
b. 6.6 kV
c. 230 V/ 400 V
d. 22 kV
ANSWER: 6.6 kV
13) What is the main drawback of overhead system over underground system?
a. Surge problem
b. High initial cost
c. Higher charging current
d. Underground system is more flexible than overhead system
ANSWER: Surge problem
14) For the same conductor length, same amount of power, same losses and maximum voltage to earth, which system requires minimum conductor area?
a. 3 wire ac
b. 2 wire ac
c. 2 wire dc
d. Single phase
ANSWER: 3 wire ac
15) What is the highest possible transmission voltage in India?
a. 675 kV
b. 765 kV
c. 132 kV
d. 440 kV
ANSWER: 765 kV
Power Systems Transmissions 5
16) What is the main reason for using the high voltage for the long distance power transmission?
a. Reduction in the transmission losses
b. Reduction in the time of transmission
c. Increase in system reliability
d. None of these
ANSWER: Reduction in the transmission losses
17) The volume of copper required in case of three wire two phase ac systems is how many times to that of two wired dc system?
a. 2/cos2φ
b. 1/2 cos2φ
c. 1.457/ cos2φ
d. 6/1.457 cos2φ
ANSWER: 1.457/ cos2φ
18) The volume of copper required in case of four wire two phase ac systems is how many times to that of two wired dc system?
a. 2/cos2φ
b. 1/2 cos2φ
c. 1.457/ cos2φ
d. 6/1.457 cos2φ
ANSWER: 1/2 cos2φ
19) By increasing the transmission voltage double of its original value, the same power can be despatched keeping the line losses _______________.
a. Equal to its original value.
b. Half of its original value.
c. Double the original value.
d. One – fourth of the original value.
ANSWER: One – fourth of the original value.
Power Systems Transmissions 5
20) Which among these is/are the fundamental economical principles that influence/s the design of transmission lines?
a. Economic choice of conductor size.
b. Economic choice of transmission voltage.
c. Both (a) and (b)
d. Economic choice of transmission line length.
ANSWER: Both (a) and (b)
21) The most economical area of conductor is that for which the total annual cost of transmission line is minimum. Which law states this?
a. Lenz’s law
b. Kelvin’s law
c. Faraday’s law
d. Ohm’s law
ANSWER: Kelvin’s law
22) The account of interest and depreciation on the capital cost of complete installation of transmission line is denoted by which factor?
a. Annual charge on capital outlay
b. Annual cost of energy wasted
c. Both (a) and (b)
d. Neither of these
ANSWER: Annual charge on capital outlay
23) The annual charge is given by
a. P1 + P2 / a
b. (P1 + P2) * a
c. P1 + P2 * a
d. P1 * a + P2
ANSWER: P1 + P2 * a
Power Systems Transmissions 5
24) The annual cost of energy wasted is given by
a. P1 / a
b. P2 * a
c. P2 / a
d. P3 / a
ANSWER: P3 / a
25) In the following graph what does the straight line represent?.
a. Relation between annual charge and the area of cross section.
b. Relation between annual cost of energy wasted and area of cross section.
c. Both (a) and (b).
d. None of these.
ANSWER: Relation between annual charge and the area of cross section.
26) In the following graph what does curve 2 represent?.
a. Relation between annual charge and the area of cross section.
b. Relation between annual cost of energy wasted and area of cross section.
c. Both (a) and (b).
d. None of these.
ANSWER: Relation between annual cost of energy wasted and area of cross section.
Power Systems Transmissions 5
27) What does the point P refer to?.
a. Most economical power transmission.
b. Most economical area of cross section.
c. Both (a) and (b).
d. Most ideal point of transmission.
ANSWER: Most economical area of cross section.
28) Which among these is not the component of over head transmission lines?
a. Conductors
b. Cross arms
c. Danger plates
d. Transformers
ANSWER: Transformers
29) Which among these properties are not suitable for the conductor material?
a. High electrical conductivity.
b. High specific gravity.
c. Lower cost.
d. High tensile strength.
ANSWER: High specific gravity.
30) What is the empirical formula to calculate the number of strands?
a. 3n (n+2n) + 2
b. 3n (n+1) + 2
c. 3n (n+1) + 1
d. 3n (3+ 3n) + 1
ANSWER: 3n (n+1) + 1
Power Systems Transmissions 5
31) The most ideal material for the over head conductor is copper. What are the advantages of this?
a. Smaller cross sectional area.
b. Area offered by the wind loads is reduced.
c. The price of copper is less.
d. Both (a) and (b).
e. None of these
ANSWER: Both (a) and (b).
32) Which among the following properties has got a higher value for aluminium in comparison to that of copper?
a. Electrical resistivity.
b. Melting point.
c. Thermal conductivity.
d. Specific gravity.
ANSWER: Electrical resistivity.
33) Why are galvanised steel conductors not suitable for transmitting large power over long distance?
a. Poor conductivity.
b. High resistance of steel.
c. More power loss.
d. Both (a) and (b).
e. None of these
ANSWER: Both (a) and (b).
34) Why are the conductors used for higher voltage transmission stranded?
a. Ease of handling.
b. Cheaper cost.
c. Reduced resistivity.
d. Increase in tensile strength.
ANSWER: Ease of handling.
Power Systems Transmissions 5
35) Which material is used for the manufacture of ground wire?
a. Aluminium
b. Galvanised steel
c. Cast iron
d. Stainless steel
ANSWER: Galvanised steel
36) The following materials of line conductor are given.
i. Hard drawn copper.
ii. Cadmium copper.
iii. Aluminium.
iv. Galvanised steel.
What is the correct series in descending order of their electrical conductivities?
a. a. i, ii, iv, iii.
b. B. ii, i, iv, iii.
c. C. ii, i, iii, iv.
d. D. i, ii, iii, iv.
ANSWER: D. i, ii, iii, iv.
37) When steel is reinforced what happens to the composite conductor?
a. 35 % more compared with equivalent weight of copper.
b. 25 % more compared with equivalent weight of copper.
c. 25 % less compared with equivalent weight of copper.
d. 35 % less compared with equivalent weight of copper.
ANSWER: 25 % less compared with equivalent weight of copper.
Power Systems Transmissions 5
38) Why is A.C.S.R conductor used as the replacement or substitute for copper?
a. Higher current carrying capacity.
b. Economy.
c. Being less weight.
d. Higher tensile strength.
ANSWER: Economy.
39) What is the function of steel wire in A.C.S.R conductors?
a. Compensate for skin effect.
b. Takes care of surges.
c. Reduced capacitance and inductance.
d. Provide additional mechanical strength.
ANSWER: Provide additional mechanical strength.
40) Why is grease added between steel and aluminium conductors?
a. To reduce the corrosion by electrolytic action.
b. To reduce friction between the strand.
c. To eliminate the air gaps.
d. To reduce the leakage of current.
ANSWER: To reduce the corrosion by electrolytic action.
Power Systems Transmissions 5
