Transmission and Distribution Mcq

1. A 3 -phase, 4-wire system is commonly used for

(a) primary distribution.
(b) secondary distribution.
(c) primary transmission.
(d) secondary transmission.

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2. 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.

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3. 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.

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4. In a transmission system the feeder supplies power to

(a) transformer substations (step-up).
(b) service mains.
(c) distributors.
(d) all of the above.

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5. 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.

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6. Distributors are designed from the point of view of

(a) its current carrying capacity.
(b) operating voltage.
(c) voltage drop in it.
(d) operating frequency.

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7. Transmission and distribution of electric power by 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.

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8. The main drawback(s) of underground system over overhead system is/are

(a) exposure to lightning.
(b) heavy initial cost.
(c) exposure to atmospheric hazards such as smoke, ice, wind etc.
(d) inductive interference between power and communication circuits.

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9. The main drawback(s) of overhead system over underground system is/are

(a) underground system is more flexible than overhead system.
(b) higher charging current.
(c) surge problem.
(d) high initial cost.

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10. By increasing the transmission voltage double of its original value, the same power can be dispatched keeping the line loss

(a) equal to its original value.
(b) half of original value.
(c) double the original value.
(d) one-fourth of original value.

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11. If a fixed amount of power is to be transmitted over certain length with fixed power loss, it can be said that volume of conductor is

(a) inversely proportional to magnitude of the voltage and that of power factor of the load.
(b) inversely proportional to square of the voltage and square of power factor of the load.
(c) proportional to square of voltage and that of power factor of the load.
(d) proportional to magnitude of the voltage only.

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12. For the same voltage drop, increasing the voltage of a distributor n-times

(a) reduces the x-section of the conductor by n times.
(b) increases the x-section of the conductor by n times.
(c) reduces the x-section of the conductor by n2 times.
(d) increases the x-section of the conductor by n2 times.

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13. The volume of copper required for an AC transmission line is inversely proportional to

(a) current.
(b) voltage.
(c) pf.
(d) both (b) and (c).

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14. Improving pf

(a) reduces current for a given output.
(b) increases losses in line.
(c) increases the cost of station equipment.

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15. For a given amount of power to be transmitted over a certain distance with fixed power loss, the volume of copper required is

(a) directly proportional to voltage.
(b) inversely proportional to voltage.
(c) inversely proportional to the square of voltage and pf of the load.
(d) directly proportional to the square of the voltage and pf of the load.

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16. For the same conductor length, same amount of power, same losses and same maximum voltage to earth, which system requires minimum conductor area?

(a) single phase AC
(b) 3 phase AC
(c) 2 wire AC
(d) 3 wire DC

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17. Which of the following distribution systems is preferred for good efficiency and high economy?

(a) Single-phase, 2-wire system.
(b) 2-phase, 3-wire system.
(c) 3-phase, 3-wire system.
(d) 3-phase, 4-wire system.

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18. The approximate cost ratio of a 220 kV, underground cable transmission and 220 kV overhead transmission is

(a) 50
(b) 25
(c) 13
(d) 5

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19. With the same maximum voltage to earth, which of the following AC systems with 0.8 pf will need more copper in comparison to DC 2-wire system?

(a) Single-phase, 2-wire (midpoint earthed).
(b) Single-phase, 3-wire (neutral half of outer).
(c) Three-phase, 3-wire.
(d) Three-phase, 4-wire (neutral = outer).

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20. The main reason for using high voltage for long distance power transmission is

(a) reduction in transmission losses.
(b) reduction in time of transmission.
(c) increase in system reliability.
(d) none of the above.

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