Power System Transmission – 100 PYQs

Q1. For a short transmission line, the receiving end voltage is always:
A) Greater than sending end
B) Less than sending end
C) Equal
D) Unpredictable
Ans: B

Q2. Ferranti effect is more pronounced in:
A) Short lines
B) Medium lines
C) Long lightly loaded lines
D) Loaded short lines
Ans: C

Q3. If reflection coefficient = 0, then:
A) No reflection
B) Full reflection
C) Open circuit
D) Short circuit
Ans: A

Q4. Surge impedance loading is maximum for:
A) Short line
B) Medium line
C) Long line
D) Independent of length
Ans: D

Q5. ABCD constants of a transmission line satisfy:
A) AD – BC = 0
B) AD – BC = 1
C) AD + BC = 0
D) AD + BC = 1
Ans: B

Q6. For 220 kV line, corona starting voltage is around:
A) 50 kV
B) 120 kV
C) 180 kV
D) 220 kV
Ans: B

Q7. Shunt compensation in transmission lines is used to:
A) Increase series reactance
B) Improve voltage profile
C) Reduce SIL
D) Reduce power factor
Ans: B

Q8. In bundled conductors, the effective inductance is:
A) Increased
B) Reduced
C) Constant
D) Zero
Ans: B

Q9. Transmission line efficiency increases when:
A) Voltage increases
B) Current decreases
C) Both A and B
D) Resistance increases
Ans: C

Q10. Corona discharge produces:
A) Ozone
B) Radio interference
C) Power loss
D) All of these
Ans: D

Q11. Reflection coefficient for matched load is:
A) +1
B) -1
C) 0
D) ∞
Ans: C

Q12. A 400 kV line with 20 discs in suspension string, the string efficiency is:
A) < 100%
B) 100%
C) > 100%
D) Not defined
Ans: A

Q13. Surge impedance of an overhead line is typically:
A) 100–200 Ω
B) 200–400 Ω
C) 500–800 Ω
D) >1000 Ω
Ans: B

Q14. In transmission lines, which parameter causes charging current?
A) Resistance
B) Inductance
C) Capacitance
D) Leakage
Ans: C

Q15. Kelvin’s law gives:
A) Maximum efficiency condition
B) Economic conductor size
C) Voltage regulation
D) Power transfer
Ans: B

Q16. For maximum power transfer in transmission line:
A) δ = 90°
B) δ = 0°
C) δ = 180°
D) δ = 45°
Ans: A

Q17. Corona loss is more at:
A) High frequency
B) Low frequency
C) Zero frequency
D) DC supply
Ans: A

Q18. String efficiency can be improved by:
A) Increasing number of discs
B) Guard ring
C) Reducing conductor spacing
D) Increasing voltage
Ans: B

Q19. A 132 kV line is classified as:
A) Low voltage
B) Medium voltage
C) High voltage
D) Extra high voltage
Ans: C

Q20. Reflection coefficient at short-circuited line is:
A) +1
B) -1
C) 0
D) ∞
Ans: B

Q21. Surge impedance loading (SIL) is given by:
A) V²/Zc
B) V/Zc
C) V²/R
D) V²/L
Ans: A

Q22. Capacitance grading of cables is done to:
A) Increase corona
B) Reduce dielectric stress
C) Reduce insulation thickness
D) Increase losses
Ans: B

Q23. The power loss due to corona is given by:
A) Peek’s formula
B) Kelvin’s formula
C) Steinmetz formula
D) Maxwell’s law
Ans: A

Q24. In a short transmission line model, which is neglected?
A) R
B) L
C) C
D) X
Ans: C

Q25. The shunt admittance of a transmission line is mainly due to:
A) Line resistance
B) Ground capacitance
C) Inductance
D) None
Ans: B

Q26. Surge impedance is:
A) √(L/C)
B) √(R/L)
C) √(L/R)
D) √(R/C)
Ans: A

Q27. Power transfer capability of a line depends on:
A) Voltage
B) Reactance
C) Load angle
D) All of these
Ans: D

Q28. Transposition of transmission line conductors is done to:
A) Reduce corona
B) Reduce interference with nearby lines
C) Equalize inductance and capacitance
D) Reduce resistance
Ans: C

Q29. Shunt reactors in EHV lines are mainly for:
A) Reactive power absorption
B) Reactive power generation
C) Voltage drop
D) Reduce resistance
Ans: A

Q30. Reflection coefficient magnitude is always:
A) ≤ 1
B) ≥ 1
C) = 0
D) = ∞
Ans: A

Q31. ACSR conductors are preferred because:
A) High strength
B) Less sag
C) Economical
D) All of these
Ans: D

Q32. Ferranti effect is absent in:
A) Short lines
B) Medium lines
C) Long lines
D) EHV lines
Ans: A

Q33. Which insulator is preferred for 400 kV lines?
A) Pin
B) Shackle
C) Suspension
D) Post
Ans: C

Q34. The surge impedance loading of a line increases with:
A) Voltage
B) Length
C) Resistance
D) Frequency
Ans: A

Q35. Radio interference due to corona is minimized by:
A) Bundle conductors
B) Ground wires
C) High resistance
D) Shunt reactors
Ans: A

Q36. The typical range of string efficiency is:
A) 40–50%
B) 60–70%
C) 70–80%
D) 90–100%
Ans: C

Q37. The Ferranti effect occurs because of:
A) Series resistance
B) Series inductance and shunt capacitance
C) Shunt conductance
D) None
Ans: B

Q38. In high-voltage transmission, the most significant line parameter is:
A) R
B) L
C) C
D) G
Ans: C

Q39. A tuned power line is one where:
A) Receiving end voltage = Sending end voltage
B) Power factor is unity
C) No reactive power
D) Line loss = 0
Ans: A

Q40. The corona inception voltage increases with:
A) Decrease in conductor diameter
B) Increase in conductor spacing
C) Increase in air density
D) Both B and C
Ans: D

Q41. For economical transmission, higher voltage is chosen to:
A) Reduce current
B) Reduce losses
C) Reduce conductor size
D) All of these
Ans: D

Q42. In cables, dielectric loss is proportional to:
A) f
B) f²
C) 1/f
D) √f
Ans: A

Q43. When a transmission line is terminated in its surge impedance:
A) No reflection
B) Full reflection
C) Maximum reflection
D) Zero transmission
Ans: A

Q44. Which tower is used for angle location in transmission lines?
A) Suspension tower
B) Tension tower
C) Guyed tower
D) None
Ans: B

Q45. Skin effect in conductors increases with:
A) Decreasing frequency
B) Increasing frequency
C) Decreasing diameter
D) None
Ans: B

Q46. In a cable, the maximum stress occurs at:
A) Conductor surface
B) Outer sheath
C) Mid-point of dielectric
D) Neutral point
Ans: A

Q47. String insulator units are connected in:
A) Series
B) Parallel
C) Both series & parallel
D) Star
Ans: A

Q48. For overhead lines, the most economical conductor shape is:
A) Square
B) Hollow
C) Circular
D) Hexagonal
Ans: C

Q49. When transmission line length increases, Ferranti effect:
A) Decreases
B) Increases
C) Remains constant
D) Zero
Ans: B

Q50. In AC transmission, efficiency increases by:
A) Increasing voltage
B) Reducing losses
C) Power factor correction
D) All of these
Ans: D

---

Q51. Which conductor arrangement reduces corona loss?
A) Single
B) Bundled
C) Twin
D) None
Ans: B

Q52. For 11 kV line, the insulator type used is:
A) Pin
B) Suspension
C) Shackle
D) Post
Ans: A

Q53. Which factor does not affect corona loss?
A) Frequency
B) Conductor surface condition
C) Current magnitude
D) Air density
Ans: C

Q54. In EHV cables, the main limitation is:
A) Corona
B) Charging current
C) Skin effect
D) Radio interference
Ans: B

Q55. Voltage regulation is negative due to:
A) Ferranti effect
B) Corona
C) Shunt reactor
D) Skin effect
Ans: A

Q56. The typical span of a transmission line tower is:
A) 10 m
B) 20 m
C) 300–400 m
D) 2000 m
Ans: C

Q57. Which factor improves string efficiency?
A) High capacitance between discs
B) Guard ring
C) Low conductor spacing
D) Increase in leakage current
Ans: B

Q58. Which transmission is more economical for long distance?
A) AC
B) DC
C) Both equal
D) None
Ans: B

Q59. Sag in a conductor increases with:
A) Decrease in span
B) Increase in temperature
C) Decrease in temperature
D) Decrease in weight
Ans: B

Q60. The safe limit of sag is governed by:
A) Tension
B) Clearance
C) Both A and B
D) None
Ans: C

---

Q61. Ferranti effect is due to:
A) Series inductance and shunt capacitance
B) Shunt resistance
C) Line losses
D) Sag
Ans: A

Q62. If sending end power factor = unity, the receiving end power factor of a short line will be:
A) Unity
B) Lagging
C) Leading
D) Zero
Ans: B

Q63. The critical disruptive voltage depends on:
A) Air density
B) Surface condition
C) Conductor diameter
D) All of these
Ans: D

Q64. Ferranti effect is more serious in:
A) Loaded lines
B) Lightly loaded lines
C) Cables
D) Transformers
Ans: B

Q65. Transmission line constant "C" is called:
A) Series impedance
B) Shunt admittance
C) Transfer constant
D) Propagation constant
Ans: B

Q66. Which parameter is neglected in a short line model?
A) Resistance
B) Reactance
C) Capacitance
D) Inductance
Ans: C

Q67. In DC transmission, which loss is absent?
A) Copper
B) Skin effect
C) Corona
D) None
Ans: B

Q68. The dielectric strength of air is approximately:
A) 1 kV/cm
B) 30 kV/cm
C) 100 kV/cm
D) 3 kV/cm
Ans: B

Q69. Reflection coefficient at open circuit =
A) +1
B) -1
C) 0
D) None
Ans: A

Q70. Critical disruptive voltage increases with:
A) Temperature rise
B) Decrease in air density
C) Increase in conductor diameter
D) Decrease in conductor spacing
Ans: C

---

Q71. SIL of a line is proportional to:
A) V
B) V²
C) 1/V
D) 1/V²
Ans: B

Q72. The efficiency of a transmission line mainly depends on:
A) Voltage
B) Current
C) Power factor
D) Resistance
Ans: A

Q73. Surge impedance of cable is:
A) Higher than overhead line
B) Lower than overhead line
C) Same
D) Infinite
Ans: B

Q74. Overhead lines are transposed to:
A) Reduce corona
B) Reduce interference with communication lines
C) Reduce resistance
D) Increase sag
Ans: B

Q75. The propagation constant of a line is:
A) √(YZ)
B) √(Z/Y)
C) Z/Y
D) Y/Z
Ans: A

Q76. The attenuation constant of a line represents:
A) Losses
B) Surge impedance
C) Velocity
D) Phase shift
Ans: A

Q77. String efficiency always:
A) Increases with number of discs
B) Decreases with number of discs
C) Remains constant
D) Independent
Ans: B

Q78. An ACSR conductor has:
A) Steel core with aluminium strands
B) Aluminium core with steel strands
C) Copper with aluminium strands
D) None
Ans: A

Q79. Sag is proportional to:
A) Span²
B) Span
C) 1/Span
D) √Span
Ans: A

Q80. For an overhead line, inductance depends upon:
A) Length
B) Spacing
C) Radius
D) All of these
Ans: D

---

Q81. Ferranti effect is mainly due to:
A) Shunt capacitance
B) Resistance
C) Inductance
D) Ground wires
Ans: A

Q82. Surge impedance is independent of:
A) Frequency
B) Inductance
C) Capacitance
D) Line length
Ans: D

Q83. The dielectric stress in cables is maximum at:
A) Core conductor
B) Sheath
C) Mid-point
D) Insulation surface
Ans: A

Q84. The critical voltage gradient for corona is reduced by:
A) Increasing conductor diameter
B) Reducing spacing
C) Using rough surface conductors
D) Increasing air density
Ans: C

Q85. Which line requires shunt reactors?
A) Short
B) Medium
C) Long
D) All
Ans: C

Q86. Ferranti effect is absent in:
A) DC lines
B) AC lines
C) Both
D) None
Ans: A

Q87. A line is called tuned when:
A) Length = λ/4
B) Length = λ/2
C) Length = λ
D) None
Ans: B

Q88. The surge impedance of a line is independent of:
A) Line length
B) Line constants
C) Frequency
D) Both A and C
Ans: D

Q89. Which tower is lightest?
A) Suspension
B) Tension
C) Terminal
D) None
Ans: A

Q90. Shunt capacitors are used for:
A) Leading VARs
B) Lagging VARs
C) Voltage drop
D) None
Ans: A

---

Q91. The Ferranti effect magnitude increases with:
A) Decrease in frequency
B) Increase in frequency
C) Decrease in length
D) None
Ans: B

Q92. The surge impedance of overhead line is about:
A) 100 Ω
B) 300–400 Ω
C) 800 Ω
D) 1000 Ω
Ans: B

Q93. The ABCD constants are used in:
A) Transmission line modeling
B) Transformers
C) Generators
D) Circuit breakers
Ans: A

Q94. Maximum power transfer in a line occurs when:
A) Line reactance = 0
B) Load angle = 90°
C) Voltage = maximum
D) None
Ans: B

Q95. Shunt reactors are connected at:
A) Sending end
B) Receiving end
C) Both ends
D) Middle
Ans: C

Q96. Insulator flashover voltage is always:
A) Greater than puncture voltage
B) Less than puncture voltage
C) Equal
D) None
Ans: B

Q97. The sag is inversely proportional to:
A) Conductor tension
B) Span²
C) Span
D) None
Ans: A

Q98. For same voltage, corona loss is more in:
A) AC
B) DC
C) Equal
D) None
Ans: A

Q99. The bundle conductor spacing is decided by:
A) Corona effect
B) Skin effect
C) Inductance
D) Capacitance
Ans: A

Q100. In a long line, receiving end voltage is higher due to:
A) Ferranti effect
B) Skin effect
C) Line losses
D) None
Ans: A

Power System Transmission – PYQs

 

Power System Transmission –  PYQs

Q201. For a short transmission line, the receiving end voltage is always:
A) Greater than sending end
B) Less than sending end
C) Equal
D) Unpredictable
Ans: B (PYQ – SSC JE)

Q202. Ferranti effect is more pronounced in:
A) Short lines
B) Medium lines
C) Long lightly loaded lines
D) Loaded short lines
Ans: C (PYQ – GATE)

Q203. If reflection coefficient = 0, then:
A) No reflection
B) Full reflection
C) Open circuit
D) Short circuit
Ans: A (PYQ)

Q204. Surge impedance loading is maximum for:
A) Short line
B) Medium line
C) Long line
D) Independent of length
Ans: D (PYQ – GATE)

Q205. ABCD constants of a transmission line satisfy:
A) AD – BC = 0
B) AD – BC = 1
C) AD + BC = 0
D) AD + BC = 1
Ans: B (PYQ – GATE)

Q206. For 220 kV line, typical corona starting voltage is around:
A) 50 kV
B) 120 kV
C) 180 kV
D) 220 kV
Ans: B (PYQ – SSC JE)

Q207. Shunt compensation in transmission lines is used to:
A) Increase series reactance
B) Improve voltage profile
C) Reduce SIL
D) Reduce power factor
Ans: B (PYQ – GATE)

Q208. In bundled conductors, the effective inductance is:
A) Increased
B) Reduced
C) Constant
D) Zero
Ans: B (PYQ – GATE)

Q209. Transmission line efficiency increases when:
A) Voltage increases
B) Current decreases
C) Both A and B
D) Resistance increases
Ans: C (PYQ)

Q210. Corona discharge produces:
A) Ozone
B) Radio interference
C) Power loss
D) All of these
Ans: D (PYQ)

Q211. Reflection coefficient for matched load is:
A) +1
B) -1
C) 0
D) ∞
Ans: C (PYQ – GATE)

Q212. A 400 kV line with 20 discs in suspension string, the string efficiency is:
A) < 100%
B) 100%
C) > 100%
D) Not defined
Ans: A (PYQ)

Q213. Surge impedance of an overhead line is typically:
A) 100–200 Ω
B) 200–400 Ω
C) 500–800 Ω
D) >1000 Ω
Ans: B (PYQ – SSC JE)

Q214. In transmission lines, which parameter causes charging current?
A) Resistance
B) Inductance
C) Capacitance
D) Leakage
Ans: C (PYQ)

Q215. Kelvin’s law gives:
A) Maximum efficiency condition
B) Economic conductor size
C) Voltage regulation
D) Power transfer
Ans: B (PYQ – IES)

Q216. For maximum power transfer in transmission line:
A) δ = 90°
B) δ = 0°
C) δ = 180°
D) δ = 45°
Ans: A (PYQ – GATE)

Q217. Corona loss is more at:
A) High frequency
B) Low frequency
C) Zero frequency
D) DC supply
Ans: A (PYQ)

Q218. String efficiency can be improved by:
A) Increasing number of discs
B) Guard ring
C) Reducing conductor spacing
D) Increasing voltage
Ans: B (PYQ)

Q219. A 132 kV line is classified as:
A) Low voltage
B) Medium voltage
C) High voltage
D) Extra high voltage
Ans: C (PYQ – SSC JE)

Q220. Reflection coefficient at short-circuited line is:
A) +1
B) -1
C) 0
D) ∞
Ans: B (PYQ)

Q221. Surge impedance loading (SIL) is given by:
A) V²/Zc
B) V/Zc
C) V²/R
D) V²/L
Ans: A (PYQ – GATE)

Q222. Capacitance grading of cables is done to:
A) Increase corona
B) Reduce dielectric stress
C) Reduce insulation thickness
D) Increase losses
Ans: B (PYQ – IES)

Q223. The power loss due to corona is given by:
A) Peek’s formula
B) Kelvin’s formula
C) Steinmetz formula
D) Maxwell’s law
Ans: A (PYQ)

Q224. In a short transmission line model, which is neglected?
A) R
B) L
C) C
D) X
Ans: C (PYQ)

Q225. The shunt admittance of a transmission line is mainly due to:
A) Line resistance
B) Ground capacitance
C) Inductance
D) None
Ans: B (PYQ)

Q226. Surge impedance is:
A) √(L/C)
B) √(R/L)
C) √(L/R)
D) √(R/C)
Ans: A (PYQ – SSC JE)

Q227. Power transfer capability of a line depends on:
A) Voltage
B) Reactance
C) Load angle
D) All of these
Ans: D (PYQ – GATE)

Q228. Transposition of transmission line conductors is done to:
A) Reduce corona
B) Reduce interference with nearby lines
C) Equalize inductance and capacitance
D) Reduce resistance
Ans: C (PYQ)

Q229. Shunt reactors in EHV lines are mainly for:
A) Reactive power absorption
B) Reactive power generation
C) Voltage drop
D) Reduce resistance
Ans: A (PYQ – GATE)

Q230. Reflection coefficient magnitude is always:
A) ≤ 1
B) ≥ 1
C) = 0
D) = ∞
Ans: A (PYQ)

Q231. ACSR conductors are preferred because:
A) High strength
B) Less sag
C) Economical
D) All of these
Ans: D (PYQ – SSC JE)

Q232. Ferranti effect is absent in:
A) Short lines
B) Medium lines
C) Long lines
D) EHV lines
Ans: A (PYQ)

Q233. Which insulator is preferred for 400 kV lines?
A) Pin
B) Shackle
C) Suspension
D) Post
Ans: C (PYQ)

Q234. The surge impedance loading of a line increases with:
A) Voltage
B) Length
C) Resistance
D) Frequency
Ans: A (PYQ)

Q235. Radio interference due to corona is minimized by:
A) Bundle conductors
B) Ground wires
C) High resistance
D) Shunt reactors
Ans: A (PYQ)

Q236. The typical range of string efficiency is:
A) 40–50%
B) 60–70%
C) 70–80%
D) 90–100%
Ans: C (PYQ – SSC JE)

Q237. The Ferranti effect occurs because of:
A) Series resistance
B) Series inductance and shunt capacitance
C) Shunt conductance
D) None
Ans: B (PYQ – GATE)

Q238. In high-voltage transmission, the most significant line parameter is:
A) R
B) L
C) C
D) G
Ans: C (PYQ)

Q239. A tuned power line is one where:
A) Receiving end voltage = Sending end voltage
B) Power factor is unity
C) No reactive power
D) Line loss = 0
Ans: A (PYQ – GATE)

Q240. The corona inception voltage increases with:
A) Decrease in conductor diameter
B) Increase in conductor spacing
C) Increase in air density
D) Both B and C
Ans: D (PYQ)

Q241. For economical transmission, higher voltage is chosen to:
A) Reduce current
B) Reduce losses
C) Reduce conductor size
D) All of these
Ans: D (PYQ)

Q242. In cables, dielectric loss is proportional to:
A) f
B) f²
C) 1/f
D) √f
Ans: A (PYQ – IES)

Q243. When a transmission line is terminated in its surge impedance:
A) No reflection
B) Full reflection
C) Maximum reflection
D) Zero transmission
Ans: A (PYQ)

Q244. Which tower is used for angle location in transmission lines?
A) Suspension tower
B) Tension tower
C) Guyed tower
D) None
Ans: B (PYQ)

Q245. Skin effect in conductors increases with:
A) Decreasing frequency
B) Increasing frequency
C) Decreasing diameter
D) None
Ans: B (PYQ)

Q246. In a cable, the maximum stress occurs at:
A) Conductor surface
B) Outer sheath
C) Mid-point of dielectric
D) Neutral point
Ans: A (PYQ)

Q247. String insulator units are connected in:
A) Series
B) Parallel
C) Both series & parallel
D) Star
Ans: A (PYQ)

Q248. For overhead lines, the most economical conductor shape is:
A) Square
B) Hollow
C) Circular
D) Hexagonal
Ans: C (PYQ)

Q249. When transmission line length increases, Ferranti effect:
A) Decreases
B) Increases
C) Remains constant
D) Zero
Ans: B (PYQ)

Q250. In AC transmission, efficiency increases by:
A) Increasing voltage
B) Reducing losses
C) Power factor correction
D) All of these
Ans: D (PYQ – GATE)

Power System Transmission – PYQs

 

Power System Transmission –  PYQs

Q151. The accuracy of digital voltmeters is usually:
A) ±0.01%
B) ±0.1%
C) ±1%
D) ±5%
Ans: B (PYQ)

Q152. The power transmitted through a transmission line is proportional to:
A) sinδ
B) cosδ
C) tanδ
D) δ
Ans: A (PYQ – GATE)

Q153. In a string of suspension insulators, the voltage across the top disc is:
A) Maximum
B) Minimum
C) Same as others
D) Zero
Ans: B (PYQ)

Q154. Surge impedance loading (SIL) of a line depends on:
A) Conductor length
B) Surge impedance and voltage
C) Power factor
D) Load current
Ans: B (PYQ – GATE)

Q155. Ferranti effect is observed when:
A) Receiving end voltage > Sending end voltage
B) Sending end voltage > Receiving end voltage
C) Both equal
D) Voltage = 0
Ans: A (PYQ)

Q156. For 400 kV EHV lines, bundle conductors are used to:
A) Increase corona
B) Reduce corona
C) Reduce sag
D) Increase losses
Ans: B (PYQ)

Q157. String efficiency of suspension insulators is:
A) Less than 100%
B) Always 100%
C) More than 100%
D) Not defined
Ans: A (PYQ)

Q158. Surge impedance of a line is √(L/C). Its unit is:
A) Ohm
B) Henry
C) Siemens
D) None
Ans: A (PYQ – SSC-JE)

Q159. In overhead transmission lines, ground wires are used for:
A) Neutral return
B) Lightning protection
C) Reducing corona
D) Voltage control
Ans: B (PYQ)

Q160. The dominant line parameter in long EHV lines is:
A) R
B) L
C) C
D) G
Ans: C (PYQ)

Q161. Corona effect increases with:
A) Smooth conductors
B) Rain and dust
C) Lower voltage
D) Lower frequency
Ans: B (PYQ)

Q162. Power transfer capability of a transmission line increases with:
A) Increase in X
B) Increase in V
C) Increase in δ
D) Both B and C
Ans: D (PYQ – GATE)

Q163. Kelvin’s law is used to determine:
A) Transmission line insulation
B) Transmission line conductor size
C) Tower height
D) Line voltage
Ans: B (PYQ)

Q164. For a short transmission line, which parameter is neglected?
A) Resistance
B) Inductance
C) Capacitance
D) Reactance
Ans: C (PYQ)

Q165. The corona loss is proportional to:
A) V²
B) (V − Vc)²
C) I²
D) f²
Ans: B (PYQ)

Q166. Which insulator is used for high-voltage transmission lines?
A) Shackle
B) Pin
C) Suspension
D) Strain
Ans: C (PYQ)

Q167. Transmission line inductance per phase depends mainly on:
A) Conductor radius and spacing
B) Voltage level
C) Load current
D) Frequency
Ans: A (PYQ – GATE)

Q168. The reflection coefficient at an open-ended line is:
A) +1
B) -1
C) 0
D) ∞
Ans: A (PYQ)

Q169. In HVDC transmission, corona loss is:
A) More severe
B) Less severe than AC
C) Same as AC
D) None
Ans: B (PYQ)

Q170. Ferranti effect is mainly due to:
A) Inductance
B) Capacitance
C) Resistance
D) Frequency
Ans: B (PYQ)

Q171. A 400 kV line requires approx. how many suspension discs?
A) 3–4
B) 8–10
C) 20–25
D) 30–35
Ans: C (PYQ)

Q172. Power factor at no-load in a transmission line is:
A) Lagging
B) Leading
C) Unity
D) Zero
Ans: B (PYQ)

Q173. Transmission efficiency is maximum when:
A) Line resistance is zero
B) Constant loss = Copper loss
C) Corona loss = I²R loss
D) Load PF = 1
Ans: B (PYQ)

Q174. Surge impedance loading of 765 kV line is about:
A) 100 MW
B) 400 MW
C) 1000 MW
D) 2000 MW
Ans: D (PYQ)

Q175. Transposition of lines is done to:
A) Reduce corona
B) Equalize mutual inductance and capacitance
C) Improve PF
D) Increase SIL
Ans: B (PYQ)

Q176. A tuned power line is one in which:
A) Receiving end voltage = Sending end voltage
B) Receiving end power = Sending end power
C) No charging current
D) No losses
Ans: A (PYQ)

Q177. Reflection coefficient at short-circuited end of a line is:
A) +1
B) -1
C) 0
D) None
Ans: B (PYQ)

Q178. Surge impedance loading is independent of:
A) Line length
B) Surge impedance
C) Voltage
D) None
Ans: A (PYQ)

Q179. String efficiency increases with:
A) More discs
B) Guard rings
C) Less shunt capacitance
D) Both B and C
Ans: D (PYQ)

Q180. Corona results in:
A) Power loss
B) Radio interference
C) Ozone formation
D) All of these
Ans: D (PYQ)

Q181. The percentage resistance of a transmission line is typically:
A) 1–2%
B) 5–10%
C) 15–20%
D) >20%
Ans: A (PYQ)

Q182. Long lines are analyzed using:
A) Equivalent circuit
B) Hyperbolic functions
C) Short line model
D) Only ABCD constants
Ans: B (PYQ – GATE)

Q183. In which weather condition is corona more severe?
A) Winter
B) Summer
C) Foggy / Rainy
D) Clear weather
Ans: C (PYQ)

Q184. Shunt reactors are used in long EHV lines for:
A) Voltage rise
B) Reactive power absorption
C) Stability
D) Improving PF
Ans: B (PYQ)

Q185. If surge impedance of a line is 400 Ω and voltage is 220 kV, the SIL is:
A) 200 MW
B) 120 MW
C) 400 MW
D) 121 MW
Ans: D (PYQ – GATE)

Q186. ACSR conductors are used because:
A) More strength
B) Less sag
C) Economical
D) All of these
Ans: D (PYQ)

Q187. Which of the following gives leading reactive power?
A) Capacitor
B) Reactor
C) Inductor
D) Resistor
Ans: A (PYQ)

Q188. For economical transmission, the most important factor is:
A) Low current
B) High voltage
C) Both A and B
D) None
Ans: C (PYQ)

Q189. String insulator voltage distribution is:
A) Uniform
B) Non-uniform
C) Always equal
D) Random
Ans: B (PYQ)

Q190. The reflection coefficient is defined as:
A) Reflected / Incident wave
B) Incident / Reflected wave
C) Transmitted / Reflected wave
D) None
Ans: A (PYQ)

Q191. The charging current is directly proportional to:
A) Voltage
B) Voltage²
C) Current
D) Resistance
Ans: A (PYQ)

Q192. The wave velocity in a transmission line is approximately:
A) 3 × 10⁸ m/s
B) 3 × 10⁶ m/s
C) 3 × 10⁵ m/s
D) None
Ans: A (PYQ)

Q193. Stability of power system is increased by:
A) Series capacitor
B) Shunt reactor
C) Reduced X
D) Both A and C
Ans: D (PYQ)

Q194. Reflection coefficient at matched load is:
A) 0
B) 1
C) -1
D) ∞
Ans: A (PYQ)

Q195. SIL of 132 kV line is about:
A) 10 MW
B) 30 MW
C) 100 MW
D) 300 MW
Ans: C (PYQ)

Q196. For maximum power transfer, the condition is:
A) Zs = Zr*
B) Zs = Zr
C) Zs = 0
D) Zs = ∞
Ans: A (PYQ)

Q197. The capacitance of a single-phase line increases when:
A) Distance between conductors decreases
B) Conductor diameter decreases
C) Both A and B
D) None
Ans: A (PYQ)

Q198. If frequency increases, skin effect:
A) Decreases
B) Increases
C) Remains same
D) Zero
Ans: B (PYQ)

Q199. Ground clearance of EHV lines is governed mainly by:
A) Safety requirements
B) Voltage level
C) Tower design
D) All of these
Ans: D (PYQ)

Q200. The maximum power in a line is given by:
A) (EV/X) sinδ
B) (EV/X) cosδ
C) (EV/X) tanδ
D) (EV/X) δ
Ans: A (PYQ – GATE)

Power System Transmission – Set 3 (Q101–Q150)

 

Power System Transmission – Set 3 (Q101–Q150)

Q101. The main cause of corona in transmission lines is:
A) Low voltage
B) High current
C) High electric field intensity
D) Low frequency
Ans: C

Q102. The unit of line charging susceptance is:
A) Siemens
B) Ohm
C) Henry
D) Farad
Ans: A

Q103. The surge impedance of a line depends on:
A) L and C per unit length
B) R and G per unit length
C) Voltage level only
D) Frequency only
Ans: A

Q104. The power transmitted over a line depends on:
A) Sending end voltage
B) Receiving end voltage
C) Line reactance
D) All of these
Ans: D

Q105. In overhead lines, the effect of wind load is to:
A) Reduce sag
B) Increase sag
C) Reduce tension
D) None
Ans: B

Q106. The dielectric strength of air under normal conditions is approximately:
A) 1 kV/cm
B) 3 kV/cm
C) 10 kV/cm
D) 30 kV/cm
Ans: B

Q107. The effect of series capacitors in transmission lines is to:
A) Increase line reactance
B) Decrease line reactance
C) Increase resistance
D) Reduce capacitance
Ans: B

Q108. The phenomenon of potential equalization in insulator string is improved by:
A) Reducing number of discs
B) Grading rings
C) Increasing string length
D) Using pin insulators
Ans: B

Q109. The reactive power flow in transmission line is proportional to:
A) V²/X
B) (EV/X) sinδ
C) (EV/X) cosδ
D) V/X
Ans: A

Q110. The propagation constant of a transmission line is:
A) √(ZY)
B) √(R/L)
C) √(L/C)
D) √(R/G)
Ans: A

Q111. For minimum corona loss, conductor surface should be:
A) Rough
B) Smooth
C) Thin
D) Sharp-edged
Ans: B

Q112. The effect of temperature on corona is:
A) Negligible
B) Increases at high temperature
C) Reduces at high temperature
D) Same at all
Ans: C

Q113. High voltage transmission lines use suspension insulators because:
A) Cheaper
B) Flexible and can be added
C) Good mechanical strength
D) All of these
Ans: D

Q114. The surge impedance loading of a line increases with:
A) Increase in surge impedance
B) Increase in voltage
C) Increase in frequency
D) Both A and B
Ans: D

Q115. In long lines, the relation between sending and receiving end quantities is given by:
A) ABCD constants
B) ZY parameters
C) Y-bus matrix
D) Load flow equations
Ans: A

Q116. In overhead lines, the ground clearance increases with:
A) Higher voltage
B) Lower voltage
C) Frequency
D) Power factor
Ans: A

Q117. String efficiency is improved by:
A) Reducing shunt capacitance
B) Using guard rings
C) Using fewer discs
D) Both A and B
Ans: D

Q118. Ferranti effect is more pronounced at:
A) Light load, long line
B) Heavy load, short line
C) Unity PF load
D) Balanced load
Ans: A

Q119. For EHV transmission, which factor dominates?
A) Line resistance
B) Line capacitance
C) Load power factor
D) Frequency
Ans: B

Q120. The major cause of transmission line losses is:
A) Corona
B) I²R loss
C) Leakage current
D) Dielectric loss
Ans: B

Q121. A lossless line means:
A) R = 0, G = 0
B) L = 0, C = 0
C) R = 0, C = 0
D) L = 0, G = 0
Ans: A

Q122. For minimum sag, the conductor tension should be:
A) Low
B) High
C) Zero
D) Moderate
Ans: B

Q123. The corona loss is least affected by:
A) Conductor surface
B) Frequency
C) Atmospheric conditions
D) Line length
Ans: D

Q124. The shunt conductance of a line accounts for:
A) Dielectric leakage
B) I²R loss
C) Corona
D) Ferranti effect
Ans: A

Q125. In a short line model, which parameters are considered?
A) R and L
B) R and C
C) L and C
D) R, L, C
Ans: A

Q126. If the length of a line is more than 250 km, it is treated as:
A) Short line
B) Medium line
C) Long line
D) None
Ans: C

Q127. Corona increases:
A) Transmission efficiency
B) Transmission loss
C) String efficiency
D) Stability
Ans: B

Q128. The wave propagation speed in a transmission line is nearly equal to:
A) Speed of sound
B) Speed of light
C) Speed of electrons
D) None
Ans: B

Q129. The surge impedance of a line is expressed in:
A) Ohms
B) Henry
C) Siemens
D) Farads
Ans: A

Q130. Bundled conductors are used in EHV lines to reduce:
A) Corona loss
B) Surge impedance
C) Line reactance
D) All of these
Ans: D

Q131. In a string of insulators, the disc nearest to the conductor has:
A) Minimum voltage
B) Maximum voltage
C) Equal voltage
D) Zero voltage
Ans: B

Q132. For economical transmission, the line voltage is increased because:
A) Current decreases
B) Losses decrease
C) Conductor size decreases
D) All of these
Ans: D

Q133. In overhead lines, earth wire is placed:
A) Below conductors
B) Above conductors
C) Side of conductors
D) Parallel at ground
Ans: B

Q134. The inductive reactance per km of a line depends on:
A) Conductor spacing and size
B) Voltage
C) Current
D) Frequency only
Ans: A

Q135. Transposition is carried out in:
A) Short lines
B) Long lines
C) Distribution lines
D) Cables
Ans: B

Q136. The characteristic impedance of a line is independent of:
A) Voltage
B) Length
C) Both A and B
D) L and C
Ans: C

Q137. The resistance of a transmission line conductor increases with:
A) Lower temperature
B) Higher temperature
C) Humidity
D) Altitude
Ans: B

Q138. Ground wires protect transmission lines from:
A) Over-voltage surges
B) Over-current
C) Corona
D) Ferranti effect
Ans: A

Q139. The reflection coefficient at a short-circuited line end is:
A) +1
B) -1
C) 0
D) ∞
Ans: B

Q140. Voltage regulation in a transmission line improves with:
A) Series capacitor
B) Shunt reactor
C) Resistance reduction
D) All of these
Ans: D

Q141. A synchronous phase modifier is used to:
A) Improve PF
B) Reduce sag
C) Control frequency
D) Eliminate corona
Ans: A

Q142. The surge impedance loading is independent of:
A) Line length
B) Voltage level
C) Surge impedance
D) None
Ans: A

Q143. For a given line, SIL is proportional to:
A) V²/Zc
B) V/Zc
C) I²R
D) (EV/X) sinδ
Ans: A

Q144. The ABCD constants of a short line are:
A = 1, D = 1, B = Z, C = 0
B = 0, C = Y, A = D = 1
C = Z, D = Y, A = 0, B = 0
None
Ans: A

Q145. For a nominal T-model, the capacitance is divided:
A) Half at each end
B) Full at middle
C) Neglected
D) Divided unequally
Ans: B

Q146. An uncompensated line at light load suffers from:
A) Voltage rise (Ferranti)
B) Voltage drop
C) Corona
D) Sag
Ans: A

Q147. For HVDC lines, corona is:
A) More severe
B) Less severe
C) Same as AC
D) Negligible
Ans: B

Q148. The surge impedance loading of 220 kV line is typically:
A) 50 MW
B) 100 MW
C) 400 MW
D) 1000 MW
Ans: C

Q149. Voltage regulation is zero when:
A) Sending voltage = Receiving voltage
B) Line is short
C) Power factor = 1
D) SIL is maximum
Ans: A

Q150. Stability of power system increases with:
A) Lower X
B) Higher V
C) Lower δ
D) All of these
Ans: D