POWER SYSTEM DISTRIBUTION – 100 MCQs 

Q1. The main function of a feeder in distribution is:
A) To deliver power to consumers directly
B) To connect substation to distributor
C) To reduce transmission loss
D) To step up voltage
Ans: B

Q2. In a distribution system, maximum voltage drop occurs in:
A) Feeder
B) Distributor
C) Service mains
D) Substation bus
Ans: B

Q3. The distributors are generally designed on the basis of:
A) Maximum current carrying capacity
B) Voltage drop
C) Loss minimization
D) Both A and B
Ans: D

Q4. For load centers far from substations, which distribution is preferred?
A) Radial
B) Ring main
C) Interconnected
D) Tree type
Ans: C

Q5. Voltage regulation is defined as:
A) Ratio of sending end voltage to receiving end voltage
B) Change in receiving end voltage from no-load to full-load
C) Losses in distribution
D) None
Ans: B

Q6. Distribution system reliability is measured by:
A) Losses
B) Outage frequency & duration
C) Load factor
D) Voltage drop
Ans: B

Q7. Which factor decides location of distribution transformer?
A) Distance of consumers
B) Load center
C) Voltage regulation
D) All of the above
Ans: D

Q8. The vector group of distribution transformer is usually:
A) Y-Y
B) Δ-Δ
C) Δ-Y
D) Y-Δ
Ans: C

Q9. The most common distribution conductor material is:
A) Copper
B) Aluminium
C) Steel
D) Aluminium with steel reinforcement
Ans: D

Q10. The voltage drop in a distributor is proportional to:
A) Current only
B) Resistance only
C) Current × resistance
D) Current² × resistance
Ans: C

Q11. Load factor is defined as:
A) Maximum demand / Average load
B) Average load / Maximum demand
C) Maximum demand / Connected load
D) Average load / Connected load
Ans: B

Q12. Demand factor is always:
A) Less than 1
B) Equal to 1
C) Greater than 1
D) Zero
Ans: A

Q13. Diversity factor is always:
A) < 1
B) = 1
C) > 1
D) 0
Ans: C

Q14. Which load has the lowest load factor?
A) Domestic
B) Commercial
C) Industrial
D) Agricultural
Ans: A

Q15. High load factor improves:
A) Efficiency
B) Reliability
C) Cost per unit
D) All of the above
Ans: D

Q16. Power factor correction in distribution reduces:
A) Real power
B) Current
C) Voltage
D) Frequency
Ans: B

Q17. Capacitors for distribution power factor improvement are usually installed at:
A) Substation
B) Consumer premises
C) Along the distributor
D) All of the above
Ans: D

Q18. In India, the permissible voltage variation at consumer end is:
A) ±1%
B) ±3%
C) ±5%
D) ±10%
Ans: C

Q19. The main advantage of interconnected system is:
A) Costlier
B) More reliable supply
C) Simple design
D) Less losses only
Ans: B

Q20. Which system requires more copper?
A) Radial
B) Ring main
C) Interconnected
D) Ring + Interconnected
Ans: B

Q21. Service mains are used to connect:
A) Substation to feeder
B) Feeder to distributor
C) Distributor to consumer
D) Transmission line to substation
Ans: C

Q22. A radial distributor is economical for:
A) Urban areas
B) Rural areas
C) Industrial load
D) Interconnected loads
Ans: B

Q23. In urban areas, the preferred system is:
A) Radial
B) Ring main
C) Tree system
D) DC system
Ans: B

Q24. The minimum permissible power factor at consumer end in India is:
A) 0.7
B) 0.8
C) 0.9
D) 1.0
Ans: B

Q25. A load curve represents:
A) Variation of voltage with time
B) Variation of load with time
C) Variation of frequency with time
D) None
Ans: B

Q26. The area under daily load curve represents:
A) Average load
B) Maximum load
C) Energy consumed
D) Demand factor
Ans: C

Q27. Annual load factor is always:
A) Less than unity
B) Equal to unity
C) Greater than unity
D) Zero
Ans: A

Q28. For the same maximum demand, higher load factor means:
A) Lower average load
B) Higher average load
C) Same average load
D) None
Ans: B

Q29. Plant capacity factor is defined as:
A) Average load / Plant capacity
B) Plant capacity / Average load
C) Plant capacity / Maximum demand
D) None
Ans: A

Q30. A good distribution system should have:
A) High efficiency
B) Reliability
C) Good voltage regulation
D) All of the above
Ans: D

Q31. Voltage unbalance in distribution system affects:
A) Transformers
B) Motors
C) Lighting loads
D) All of the above
Ans: D

Q32. Unbalanced loading in a 3-phase 4-wire system causes:
A) Harmonics
B) Neutral current
C) Overvoltage
D) Overfrequency
Ans: B

Q33. Which factor increases distribution losses?
A) High current
B) Low voltage
C) Poor power factor
D) All of the above
Ans: D

Q34. Skin effect is:
A) Concentration of current near conductor surface
B) Flow of current in conductor core
C) Increase in resistance with frequency
D) Both A and C
Ans: D

Q35. Proximity effect occurs due to:
A) Skin effect
B) Mutual induction between conductors
C) Resistance variation
D) Corona discharge
Ans: B

Q36. Corona effect in distribution lines is:
A) More at high voltage
B) More at low voltage
C) Independent of voltage
D) Negligible at 11 kV
Ans: D

Q37. Which device protects distribution lines from lightning?
A) Circuit breaker
B) Lightning arrester
C) Isolator
D) Fuse
Ans: B

Q38. Which device automatically isolates a faulty section of distribution?
A) Circuit breaker
B) Isolator
C) Fuse
D) All of the above
Ans: D

Q39. The most common earthing method in distribution is:
A) Plate earthing
B) Rod earthing
C) Pipe earthing
D) Any of the above depending on soil
Ans: D

Q40. Earth resistance should be:
A) Very high
B) Very low
C) Infinite
D) Zero
Ans: B

Q41. Which conductor arrangement gives minimum reactance?
A) Flat
B) Vertical
C) Transposed
D) Horizontal
Ans: C

Q42. Transposition of conductors is done to:
A) Reduce resistance
B) Reduce reactance imbalance
C) Reduce power factor
D) Reduce losses
Ans: B

Q43. The per-unit system is used in distribution to:
A) Normalize values
B) Simplify calculations
C) Compare systems of different ratings
D) All of the above
Ans: D

Q44. In rural distribution, the predominant load is:
A) Lighting
B) Irrigation pumps
C) Industrial motors
D) Commercial shops
Ans: B

Q45. Which equipment is used to stabilize voltage in distribution?
A) Tap changing transformer
B) Voltage stabilizer
C) Booster transformer
D) All of the above
Ans: D

Q46. Automatic load control in distribution is required to maintain:
A) Constant frequency
B) Constant voltage
C) Constant current
D) Constant power factor
Ans: A

Q47. Ferranti effect is:
A) Rise of receiving end voltage under light load
B) Fall of receiving end voltage under light load
C) Rise of sending end voltage
D) Fall of sending end voltage
Ans: A

Q48. Ferranti effect is more prominent in:
A) Short distribution lines
B) Long lightly loaded lines
C) Heavy load conditions
D) None
Ans: B

Q49. Which is NOT a method of voltage control in distribution?
A) Shunt capacitor
B) Tap changing transformer
C) Booster transformer
D) Induction motor
Ans: D

Q50. Arc suppression coil is used in:
A) Overcurrent protection
B) Earth fault protection
C) Lightning protection
D) Overvoltage protection
Ans: B

Q51. Automatic reclosing circuit breakers are used in distribution to:
A) Clear permanent faults
B) Clear transient faults
C) Maintain power factor
D) Improve efficiency
Ans: B

Q52. Distribution transformer rating is generally:
A) Above 1000 kVA
B) 25 kVA to 5000 kVA
C) Below 25 kVA
D) Above 10 MVA
Ans: B

Q53. No-load losses of distribution transformer are mainly due to:
A) Resistance
B) Leakage reactance
C) Core losses
D) Copper losses
Ans: C

Q54. Full-load losses in distribution transformer are mainly:
A) Core loss
B) Copper loss
C) Dielectric loss
D) Eddy current
Ans: B

Q55. Distribution transformer is designed for maximum efficiency at:
A) 25% load
B) 50% load
C) 75% load
D) Full load
Ans: C

Q56. Which type of transformer is mostly used in distribution?
A) Core type
B) Shell type
C) Auto transformer
D) Isolation transformer
Ans: B

Q57. The efficiency of distribution transformers is:
A) 50–60%
B) 60–70%
C) 90–98%
D) 40–50%
Ans: C

Q58. Vector group Dy11 of transformer means:
A) Delta primary, star secondary with 30° lag
B) Delta primary, star secondary with 30° lead
C) Star primary, delta secondary with 30° lag
D) Star primary, delta secondary with 30° lead
Ans: A

Q59. Pole-mounted distribution transformers are usually up to:
A) 25 kVA
B) 63 kVA
C) 250 kVA
D) 1000 kVA
Ans: C

Q60. Ground mounted distribution substations are usually:
A) 250 kVA and above
B) 100 kVA and below
C) 10 kVA only
D) None
Ans: A

Q61. Sectionalizers are used in distribution lines to:
A) Interrupt load current
B) Isolate faulty sections
C) Step down voltage
D) Improve power factor
Ans: B

Q62. A fuse is primarily used for:
A) Over-voltage protection
B) Over-current protection
C) Power factor improvement
D) Frequency stability
Ans: B

Q63. Rewirable fuses are also called:
A) High-rupturing capacity fuses
B) Kit-kat fuses
C) Cartridge fuses
D) Oil fuses
Ans: B

Q64. High rupturing capacity fuses are used for:
A) Low voltage only
B) High voltage systems
C) Both low and high voltage
D) None
Ans: B

Q65. The main limitation of fuse protection is:
A) Expensive
B) Cannot protect against short-circuit
C) After operation it must be replaced
D) None
Ans: C

Q66. Which breaker is most common in distribution?
A) Air circuit breaker
B) Oil circuit breaker
C) Vacuum circuit breaker
D) SF6 circuit breaker
Ans: C

Q67. Reclosers in distribution are mainly:
A) Air CB
B) Oil CB
C) Vacuum CB
D) All of the above depending on rating
Ans: D

Q68. Which relay is most common in distribution system?
A) Overcurrent relay
B) Differential relay
C) Distance relay
D) Directional relay
Ans: A

Q69. Ground fault relays are usually:
A) Instantaneous
B) Time delayed
C) Both
D) None
Ans: C

Q70. Distribution line insulators are mainly:
A) Pin type
B) Suspension type
C) Strain type
D) All depending on voltage
Ans: D

Q71. Pin type insulators are used up to:
A) 11 kV
B) 33 kV
C) 66 kV
D) 132 kV
Ans: B

Q72. Suspension insulators are preferred above:
A) 11 kV
B) 33 kV
C) 66 kV
D) 132 kV
Ans: C

Q73. Strain insulators are used for:
A) Line supports
B) Dead ends
C) Angle poles
D) Both B and C
Ans: D

Q74. Which distribution system has least copper requirement?
A) DC 2-wire
B) DC 3-wire
C) Single phase AC
D) Three phase 4-wire
Ans: D

Q75. Copper saving in 3-phase 4-wire system compared to DC 2-wire is about:
A) 25%
B) 33%
C) 50%
D) 75%
Ans: C

Q76. The main cause of low power factor in distribution is:
A) Heating loads
B) Motor loads
C) Lighting loads
D) All of the above
Ans: B

Q77. Power factor penalty is imposed on:
A) Residential loads
B) Commercial loads
C) Industrial loads
D) All of the above
Ans: C

Q78. Distribution automation helps in:
A) Load control
B) Fault detection
C) Remote switching
D) All of the above
Ans: D

Q79. SCADA in distribution means:
A) Supervisory Control and Data Acquisition
B) Super Control and Direct Automation
C) System Control and Data Analysis
D) None
Ans: A

Q80. Smart grid in distribution ensures:
A) Automatic fault isolation
B) Demand side management
C) Integration of renewable energy
D) All of the above
Ans: D

Q81. The smart meter measures:
A) Voltage only
B) Current only
C) Energy with time stamping
D) Frequency only
Ans: C

Q82. GIS in distribution means:
A) Gas Insulated Switchgear
B) Geographic Information System
C) Both depending on context
D) None
Ans: C

Q83. Ring main unit (RMU) is used in:
A) Transmission
B) Distribution
C) Generation
D) Protection only
Ans: B

Q84. RMU normally operates at:
A) 400 V
B) 11 kV
C) 33 kV
D) 66 kV
Ans: B

Q85. In India, maximum demand tariff is mainly applicable to:
A) Domestic consumers
B) Industrial consumers
C) Agricultural consumers
D) All consumers
Ans: B

Q86. TOD tariff means:
A) Tariff on demand
B) Tariff on duration
C) Time of Day tariff
D) Total optimum demand tariff
Ans: C

Q87. TOD tariff encourages:
A) Load shifting
B) Peak demand reduction
C) Better load factor
D) All of the above
Ans: D

Q88. Which load is considered as base load in distribution?
A) Lighting
B) Industrial
C) Residential
D) Commercial
Ans: B

Q89. Load duration curve is derived from:
A) Daily load curve
B) Monthly load curve
C) Annual load curve
D) Any load curve
Ans: A

Q90. The area under load duration curve gives:
A) Maximum demand
B) Energy consumed
C) Load factor
D) Diversity factor
Ans: B

Q91. Cold reserve in power system is:
A) Standby plant kept running
B) Standby plant kept off but available
C) Plant with zero efficiency
D) None
Ans: B

Q92. Hot reserve is:
A) Plant kept running but not loaded
B) Plant shut down
C) Plant running at full load
D) Plant with low efficiency
Ans: A

Q93. Spinning reserve is:
A) Extra generating capacity available on running machines
B) Standby machine not running
C) Unused capacity of transmission
D) None
Ans: A

Q94. Distribution reliability index SAIDI measures:
A) Frequency of interruptions
B) Duration of interruptions
C) Power factor
D) Voltage regulation
Ans: B

Q95. SAIFI measures:
A) Frequency of interruptions
B) Duration of interruptions
C) Energy consumption
D) Losses
Ans: A

Q96. CAIDI is defined as:
A) SAIDI/SAIFI
B) SAIFI/SAIDI
C) Energy/Load
D) Demand/Average load
Ans: A

Q97. Availability of distribution system is:
A) 1 – Outage time/Total time
B) Outage time/Total time
C) Load factor × Diversity factor
D) Reliability × Efficiency
Ans: A

Q98. Which reduces copper requirement?
A) High voltage distribution
B) Low voltage distribution
C) High current
D) Low power factor
Ans: A

Q99. EHVAC is usually not used for distribution because:
A) Corona loss
B) Insulation requirement
C) High cost
D) All of the above
Ans: D

Q100. A good distribution system must satisfy:
A) Reliability
B) Proper voltage regulation
C) Economy
D) All of the above
Ans: D