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Transmission and Distribution MCQ Question and Answer

Transmission and Distribution MCQ Question and Answer

1.Transmission line connects 

  • AGenerating station to a switching station/step-down transformer station.
  • BStep-down transformer station to service transformer banks.
  • CDistribution transformer to consumer premises. 
  • DService points to consumer premises.
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Correct Answer : (A)

Generating station to a switching station/step-down transformer station.

Explanation:

Transmission line connects Generating station to a switching station/step-down transformer station.

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

  • APrimary Distribution
  • BSecondary Distribution
  • CPrimary Transmission
  • DSecondary Transmission
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Correct Answer : (B)

Secondary Distribution

Explanation:

A 3-phase 4-wire system is commonly used for Secondary Distribution.

3.The rated voltage of a 3-phase power is given as 

  • ARMS phase voltage 
  • BPeak phase voltage
  • CRMS line to  line voltage
  • DPeak line to  line voltage
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Correct Answer : (C)

RMS line to  line voltage

Explanation:

The rated voltage of a 3-phase power is given as  RMS line to  line voltage.

4.Which of the following is usually not the generating voltage?

  • A6.6 kV
  • B9.9 kV
  • C11 kV
  • D13.2 kV
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Correct Answer : (B)

9.9 kV

Explanation:

9.9 kV is usually not the generating voltage.

5.In a Transmission system the feeder supplies power to 

  • ATransformer substations (step-up)
  • BService mains
  • CDistributors 
  • DAll of the above 
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Correct Answer : (C)

Distributors 

Explanation:

In a Transmission system the feeder supplies power to Distributors.

6.Feeder is designed mainly from the point of view of 

  • AIts current carrying capacity
  • BVoltage drop in it
  • COperating voltage
  • DOperating frequency 
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Correct Answer : (A)

Its current carrying capacity

Explanation:

Feeder is designed mainly from the point of view of Its current carrying capacity.

7.Distributors are designed from the point of view of

  • AIts current carrying capacity
  • BOperating voltage 
  • CVoltage drop in it
  • DOperating frequency
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Correct Answer : (C)

Voltage drop in it

Explanation:

Distributors are designed from the point of view of Voltage drop in it.

8.Transmission and Distribution of electric power by underground system is superior to overhead system in respect of

  • AAppearance and public safety
  • BMaintenance cost
  • CFrequency of faults, power failure and accidents 
  • DAll of the above 
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Correct Answer : (D)

All of the above 

Explanation:

Transmission and Distribution of electric power by underground system is superior to overhead system in respect of Appearance and public safety, Maintenance cost and Frequency of faults, power failure and accidents.

9.The main drawback of underground system over overhead system  is

  • AExposure to lightning 
  • BHeavy initial cost
  • CExposure to atmospheric hazards such as smoke, ice, wind etc.
  • DInductive interference between power and communication circuits.
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Correct Answer : (B)

Heavy initial cost

Explanation:

The main drawback of underground system over overhead system  is Heavy initial cost.

10.The main drawback of overhead system over underground system  is

  • AUnderground system is more flexible than overhead system
  • BHigher charging current
  • CSurge problem
  • DHigh initial cost 
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Correct Answer : (C)

Surge problem

Explanation:

The main drawback of overhead system over underground system  is Surge problem.

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

  • AEqual to  its original value
  • BHalf of original value
  • CDouble the original value
  • DOne-fourth of original value
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Correct Answer : (D)

One-fourth of original value

Explanation:

By increasing the Transmission voltage double of its original value, the same power can be dispatched keeping the line loss One-fourth of original value.

12.The volume of copper required for an ac Transmission line is inversely proportional to 

  • ACurrent
  • BVoltage
  • Cpf
  • DBoth (b) and (c) 
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Correct Answer : (D)

Both (b) and (c) 

Explanation:

The volume of copper required for an ac Transmission line is inversely proportional to Voltage and Power factor.

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

  • ASingle-phase ac
  • B3-phase ac
  • C2-wire ac
  • D3-wire dc 
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Correct Answer : (D)

3-wire dc 

Explanation:

For the same conductor length, same amount of power, same losses and same maximum voltage to earth, The system required minimum conductor area is 3-wire dc.

14.Which of the following distribution system is preferred for good efficiency and high economy?

  • ASingle-phase, 2-wire system 
  • B2-phase, 3-wire system 
  • C3-phase, 3-wire system
  • D3-phase, 4-wire system
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Correct Answer : (D)

3-phase, 4-wire system

Explanation:

3-phase, 4-wire system distribution system is preferred for good efficiency and high economy.

15.The approximate cost ratio of a  220 kV underground cable transmission and  220 kV O/H transmission is

  • A50
  • B25
  • C13
  • D5
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Correct Answer : (C)

13

Explanation:

The approximate cost ratio of a  220 kV underground cable transmission and  220 kV O/H transmission is 13.

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

  • AReduction in transmission losses.
  • BReduction in time of transmission.
  • CIncrease in system reliability 
  • DNone of the above 
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Correct Answer : (A)

Reduction in transmission losses.

Explanation:

The main reason for using high voltage for long distance power transmission is reduction in transmission losses.

17.66 kV is suitable for transmission of power over 

  • A30 km
  • B60 km
  • C120 km
  • D200 km 
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Correct Answer : (B)

60 km

Explanation:

66 kV is suitable for transmission of power over 60 km.

18.If  3 MW  power is to be transmitted over a distance of  30 km,  the desirable transmission voltage will be 

  • A11 kV
  • B33 kV
  • C66 kV
  • D3.3 kV
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Correct Answer : (B)

33 kV

Explanation:

If  3 MW  power is to be transmitted over a distance of  30 km,  the desirable transmission voltage will be 33 kV.

19.The highest transmission voltage used in India is

  • A400 kV
  • B220 kV
  • C132 kV
  • D765 kV
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Correct Answer : (D)

765 kV

Explanation:

The highest transmission voltage used in India is 765 kV.

20.If variable part of annual cost on account of interest and depreciation on the capital out lay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be the most economical. This statement is known as 

  • ALenz?s Law
  • BKelvin?s Law 
  • CFaraday?s Law 
  • DOhm?s Law 
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Correct Answer : (B)

Kelvin?s Law 

Explanation: