Transmission Line Protection MCQs (301–340)
Q01. The main function of transmission line protection is:
A) Fault detection and isolation
B) Load balancing
C) Voltage regulation
D) Frequency control
Ans: A
Q02. Distance protection operates on:
A) Ratio of voltage to current
B) Product of voltage and current
C) Difference between voltage and current
D) Power factor angle
Ans: A
Q03. Impedance relay operates when:
A) Z < Zset
B) Z > Zset
C) V = 0
D) I = 0
Ans: A
Q04. Reactance relay operates on:
A) X < Xset
B) R < Rset
C) V/I
D) None
Ans: A
Q05. Mho relay characteristic is a:
A) Circle passing through origin
B) Straight line
C) Parabola
D) Rectangle
Ans: A
Q06. The most suitable relay for long transmission lines is:
A) Mho relay
B) Overcurrent relay
C) Reactance relay
D) Impedance relay
Ans: A
Q07. For short transmission lines, the preferred relay is:
A) Overcurrent relay
B) Distance relay
C) Differential relay
D) Mho relay
Ans: A
Q08. The zone-1 reach of a distance relay is usually set to:
A) 80–90% of line length
B) 100%
C) 50%
D) 110%
Ans: A
Q09. Zone-2 of distance relay covers:
A) Protected line + 50% of next line
B) Only the protected line
C) 100% of next line
D) None
Ans: A
Q10. Zone-3 is used for:
A) Backup protection
B) Primary protection
C) Busbar protection
D) None
Ans: A
Q11. Carrier current protection is used for:
A) Long EHV lines
B) Short lines
C) Distribution systems
D) Transformers
Ans: A
Q12. A current differential protection compares:
A) Current entering and leaving the line section
B) Voltages
C) Powers
D) Frequencies
Ans: A
Q13. A static relay uses:
A) Electronic circuits
B) Electromechanical parts
C) Thermal sensing
D) Pneumatic control
Ans: A
Q14. Numerical relays are based on:
A) Microprocessor
B) Electromagnetic coils
C) Analog circuits
D) Mechanical discs
Ans: A
Q15. The speed of operation of distance protection is:
A) High
B) Moderate
C) Low
D) None
Ans: A
Q16. Auto-reclosing improves:
A) System stability
B) Fault level
C) Current magnitude
D) None
Ans: A
Q17. The reach of a distance relay depends on:
A) Source impedance
B) Line impedance
C) Both
D) None
Ans: C
Q18. Pilot wire protection is used for:
A) Short transmission lines
B) Long lines
C) EHV systems
D) None
Ans: A
Q19. Time-graded protection is suitable for:
A) Radial feeders
B) Ring main
C) Mesh systems
D) None
Ans: A
Q20. The main disadvantage of overcurrent relay for long lines is:
A) Slow speed
B) Inaccuracy
C) Coordination problem
D) All
Ans: D
Q21. The relay that responds to both magnitude and phase angle of current is:
A) Directional relay
B) Overcurrent relay
C) Differential relay
D) Distance relay
Ans: A
Q22. A solid-state relay is immune to:
A) Shock and vibration
B) Thermal drift
C) Voltage surge
D) None
Ans: A
Q23. The operating torque of induction disc relay is proportional to:
A) V × I × sin φ
B) V × I × cos φ
C) V/I
D) I²
Ans: B
Q24. A Buchholz relay protects:
A) Transformer
B) Transmission line
C) Generator
D) Motor
Ans: A
Q25. Differential protection is most suitable for:
A) Transformers and generators
B) Transmission lines
C) Motors
D) Reactors
Ans: A
Q26. Current transformer saturation may cause:
A) Mal-operation of relays
B) Faster tripping
C) Overvoltage
D) None
Ans: A
Q27. In EHV systems, the preferred protection is:
A) Distance protection with carrier
B) Overcurrent
C) Thermal relay
D) None
Ans: A
Q28. Arc suppression coil is used in:
A) Resonant grounded system
B) Solidly grounded system
C) Ungrounded system
D) None
Ans: A
Q29. The communication channel used in carrier protection is usually:
A) Power line carrier
B) Microwave link
C) Fiber optic
D) Any of these
Ans: D
Q30. For high-speed protection, the preferred scheme is:
A) Distance with carrier intertripping
B) Time-graded overcurrent
C) Differential
D) None
Ans: A
⚡ Corona & Line Loss MCQs (341–360)
Q41. Corona loss increases with:
A) Line voltage
B) Frequency
C) Rough conductor surface
D) All
Ans: D
Q42. Corona loss per phase is given by:
A)
B)
C)
D) None
Ans: A
Q43. Audible noise from corona increases with:
A) Voltage and humidity
B) Temperature
C) Line length
D) None
Ans: A
Q44. Corona is reduced by:
A) Increasing conductor diameter
B) Bundled conductors
C) Smooth surface
D) All
Ans: D
Q45. Corona discharge produces:
A) Ozone and nitrogen oxides
B) CO₂
C) Hydrogen
D) None
Ans: A
Q46. The critical disruptive voltage depends on:
A) Air density
B) Surface irregularities
C) Conductor spacing
D) All
Ans: D
Q47. Visual corona appears at:
A) Higher voltage than disruptive voltage
B) Lower voltage
C) Same voltage
D) None
Ans: A
Q48. The effect of weather on corona loss is:
A) Rain increases loss
B) Fog increases loss
C) Both
D) None
Ans: C
Q49. Corona loss is negligible below:
A) 33 kV
B) 66 kV
C) 132 kV
D) 220 kV
Ans: B
Q50. Bundled conductors are used in EHV lines to:
A) Reduce corona
B) Reduce reactance
C) Increase power transfer
D) All
Ans: D
Q51. The corona inception voltage is proportional to:
A) Air density × spacing / radius
B) Radius / spacing
C) Spacing × radius
D) None
Ans: A
Q52. Corona results in:
A) Power loss
B) Radio interference
C) Audible noise
D) All
Ans: D
Q53. A higher air density factor reduces:
A) Corona loss
B) Voltage
C) Efficiency
D) None
Ans: A
Q54. Typical corona loss in EHV lines is of order:
A) Few kW/km/phase
B) MW/km
C) W/km
D) None
Ans: A
Q55. Corona power loss increases rapidly when voltage:
A) Exceeds critical value
B) Decreases
C) Is constant
D) None
Ans: A
⚡ HVDC Transmission MCQs (361–380)
Q61. HVDC stands for:
A) High Voltage Direct Current
B) High Voltage Double Circuit
C) High Voltage Damped Circuit
D) None
Ans: A
Q62. Main advantage of HVDC transmission is:
A) No reactive power
B) No skin effect
C) Long-distance efficiency
D) All
Ans: D
Q63. HVDC link types are:
A) Monopolar, Bipolar, Homopolar
B) Parallel, Series
C) Delta, Star
D) None
Ans: A
Q64. Typical converter stations in HVDC use:
A) Thyristors
B) IGBTs
C) Mercury arc valves
D) All
Ans: A
Q65. Converter used at rectifier end:
A) 6-pulse bridge
B) 12-pulse bridge
C) Both
D) None
Ans: C
Q66. Commutation overlap in HVDC converters causes:
A) Reduction in DC voltage
B) Increase in harmonics
C) Both
D) None
Ans: C
Q67. Typical DC link voltage in HVDC systems is:
A) ±500 kV
B) ±220 kV
C) ±33 kV
D) None
Ans: A
Q68. HVDC transmission is preferred for:
A) Long distance
B) Undersea cables
C) Interconnecting unsynchronized grids
D) All
Ans: D
Q69. The main disadvantage of HVDC is:
A) High converter cost
B) Complex control
C) Maintenance
D) All
Ans: D
Q70. Power reversal in HVDC is achieved by:
A) Reversing voltage polarity
B) Reversing current direction
C) Reversing both
D) None
Ans: B
Q71. HVDC system losses are typically:
A) 3–4% per 1000 km
B) 10%
C) 20%
D) None
Ans: A
Q72. The smoothing reactor in HVDC system:
A) Reduces ripple
B) Limits current
C) Both
D) None
Ans: C
Q73. The converter transformer provides:
A) Voltage matching and isolation
B) Current amplification
C) Frequency change
D) None
Ans: A
Q74. The commutation failure occurs due to:
A) Voltage dips in AC system
B) Excessive current
C) Both
D) None
Ans: C
Q75. Modern HVDC uses:
A) Thyristor-based LCC
B) Voltage Source Converter (VSC)
C) Both
D) None
Ans: C
Q76. The voltage polarity in bipolar HVDC system is:
A) ±V
B) 0 to +V
C) 0 to –V
D) None
Ans: A
Q77. HVDC back-to-back link connects:
A) Two asynchronous AC systems
B) Same grid
C) DC to DC
D) None
Ans: A
Q78. The main reactive power requirement in HVDC is for:
A) Converter operation
B) Transmission line
C) Cable losses
D) None
Ans: A
Q79. The HVDC line does not require:
A) Synchronization
B) Reactive compensation
C) Both (in general)
D) None
Ans: C
Q80. The power factor of HVDC converter station is usually:
A) Lagging
B) Leading
C) Unity
D) None
Ans: A
⚙️ FACTS Devices MCQs (381–400)
Q81. FACTS stands for:
A) Flexible AC Transmission System
B) Fast AC Transfer System
C) Field Aligned Control Transmission System
D) None
Ans: A
Q82. FACTS devices are used to:
A) Improve voltage stability
B) Control power flow
C) Increase transfer capability
D) All
Ans: D
Q83. Series compensation in FACTS is provided by:
A) TCSC
B) SSSC
C) Both
D) None
Ans: C
Q84. Shunt compensation in FACTS is provided by:
A) SVC
B) STATCOM
C) Both
D) None
Ans: C
Q85. TCSC stands for:
A) Thyristor Controlled Series Capacitor
B) Transmission Controlled Static Converter
C) Transformer Controlled Series Compensator
D) None
Ans: A
Q86. SVC operates by controlling:
A) Reactive power
B) Active power
C) Frequency
D) None
Ans: A
Q87. STATCOM is based on:
A) Voltage Source Converter
B) Current Source Converter
C) Both
D) None
Ans: A
Q88. SVC can operate in:
A) Capacitive and inductive mode
B) Only capacitive
C) Only inductive
D) None
Ans: A
Q89. UPFC stands for:
A) Unified Power Flow Controller
B) Universal Power Factor Compensator
C) Unidirectional Power Flow Converter
D) None
Ans: A
Q90. UPFC controls:
A) Voltage, impedance, and phase angle
B) Frequency only
C) Load only
D) None
Ans: A
Q91. The V-I characteristic of SVC is:
A) Drooping
B) Constant current
C) Constant voltage
D) None
Ans: A
Q92. STATCOM provides better performance than SVC at:
A) Low voltage
B) High voltage
C) Constant current
D) None
Ans: A
Q93. The response time of STATCOM is typically:
A) Less than 20 ms
B) 100 ms
C) 1 s
D) None
Ans: A
Q94. SSSC injects:
A) Series voltage
B) Shunt current
C) Reactive current
D) None
Ans: A
Q95. FACTS controllers improve:
A) Transient stability
B) Damping
C) Power oscillation control
D) All
Ans: D
Q96. The control element in TCSC is:
A) Thyristor
B) IGBT
C) Diode
D) None
Ans: A
Q97. The main limitation of SVC is:
A) Limited dynamic response
B) Large size
C) Harmonic generation
D) All
Ans: D
Q98. The UPFC is a combination of:
A) STATCOM + SSSC
B) STATCOM + TCSC
C) SVC + SSSC
D) None
Ans: A
Q99. The main benefit of FACTS devices is:
A) Better control of power flow
B) Improved voltage profile
C) Enhanced stability
D) All
Ans: D
Q100. The dynamic reactive power compensator in modern systems is:
A) STATCOM
B) SVC
C) TCSC
D) None
Ans: A
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