Power System Transmission – Top 50 MCQs

 

Power System Transmission – Top 50 MCQs

Q1. The main purpose of a transmission line is:
A) Generate power
B) Step up voltage
C) Transfer power
D) Regulate frequency
Ans: C

Q2. The skin effect in transmission lines increases with:
A) Decreasing frequency
B) Increasing frequency
C) Increasing resistivity
D) Decreasing diameter
Ans: B

Q3. Bundled conductors are primarily used to:
A) Reduce corona
B) Reduce resistance
C) Increase current
D) Increase voltage
Ans: A

Q4. Ferranti effect occurs in:
A) Short lines
B) Medium lines
C) Long lines
D) All lengths
Ans: C

Q5. The efficiency of transmission increases with:
A) Low voltage
B) High voltage
C) High resistance
D) Low frequency
Ans: B

Q6. In a short transmission line model, which parameter is neglected?
A) R
B) L
C) C
D) G
Ans: C

Q7. Corona loss is proportional to:
A) V
B) V²
C) (V - Vc)²
D) (V + Vc)²
Ans: C

Q8. A 3-phase transmission line with transposition helps to:
A) Reduce resistance
B) Balance mutual inductance
C) Reduce corona
D) Increase frequency
Ans: B

Q9. Surge impedance of a line is:
A) √(L/C)
B) √(C/L)
C) √(R/G)
D) √(G/R)
Ans: A

Q10. The typical value of power factor in transmission is maintained:
A) 0.2–0.3
B) 0.5–0.6
C) 0.85–0.95
D) 1.0
Ans: C

Q11. Transmission lines are transposed to:
A) Reduce voltage drop
B) Balance capacitance and inductance
C) Increase power factor
D) Eliminate resistance
Ans: B

Q12. Corona is more severe in:
A) DC lines
B) AC lines
C) Both same
D) None
Ans: B

Q13. String efficiency of suspension insulators is improved by:
A) Increasing number of discs
B) Decreasing mutual capacitance
C) Grading rings
D) Shorter string
Ans: C

Q14. The medium transmission line model is:
A) π-model or T-model
B) Only T-model
C) Only π-model
D) Neglects capacitance
Ans: A

Q15. Transmission lines are classified into short, medium, and long based on:
A) Current
B) Voltage
C) Length
D) Frequency
Ans: C

Q16. The power transmitted over a line is maximum when:
A) δ = 0°
B) δ = 45°
C) δ = 90°
D) δ = 180°
Ans: C

Q17. Corona inception voltage depends on:
A) Line length
B) Conductor size and spacing
C) Load
D) Frequency only
Ans: B

Q18. Ferranti effect is due to:
A) Inductance
B) Capacitance
C) Resistance
D) Frequency
Ans: B

Q19. A double circuit line is used to:
A) Reduce sag
B) Increase reliability
C) Reduce resistance
D) Increase frequency
Ans: B

Q20. Overhead lines are preferred over underground cables because:
A) Cheaper
B) Higher losses
C) Less reliable
D) Difficult maintenance
Ans: A

Q21. Surge impedance loading (SIL) depends on:
A) Line resistance
B) Surge impedance
C) Power factor
D) Length
Ans: B

Q22. In HVAC transmission, line inductance causes:
A) Lagging VARs
B) Leading VARs
C) Unity PF
D) Zero current
Ans: A

Q23. For EHV lines, the dominant line parameter is:
A) Resistance
B) Inductance
C) Capacitance
D) Frequency
Ans: C

Q24. The sag in transmission lines increases with:
A) Increase in conductor weight
B) Decrease in span length
C) Decrease in temperature
D) Increase in tension
Ans: A

Q25. HVDC transmission has advantage over HVAC because:
A) Higher losses
B) No reactive power
C) Corona is severe
D) High insulation
Ans: B

Q26. Insulator string is used in transmission lines to:
A) Support conductors
B) Reduce sag
C) Transpose lines
D) Control corona
Ans: A

Q27. The most common conductor material for transmission lines is:
A) Copper
B) Aluminium
C) ACSR
D) Steel
Ans: C

Q28. Corona discharge produces:
A) Ozone
B) Nitrogen
C) Sulphur
D) Carbon
Ans: A

Q29. In long lines, the effect of line capacitance is:
A) Negligible
B) Dominant
C) Same as resistance
D) None
Ans: B

Q30. Which one is not a method of reducing corona?
A) Increasing conductor size
B) Reducing spacing
C) Using bundled conductors
D) Using smooth conductors
Ans: B

Q31. The maximum sag is in which season?
A) Summer
B) Winter
C) Rainy
D) Monsoon
Ans: A

Q32. Nominal π-model is preferred over T-model for:
A) Short lines
B) Medium lines
C) Long lines
D) None
Ans: B

Q33. The effect of proximity increases with:
A) Higher frequency
B) Lower frequency
C) Lower current
D) DC supply
Ans: A

Q34. The receiving end voltage in Ferranti effect is:
A) Less than sending end
B) More than sending end
C) Equal
D) Zero
Ans: B

Q35. Stability of a transmission system improves with:
A) Decreasing X
B) Increasing X
C) Decreasing V
D) Decreasing f
Ans: A

Q36. HVDC system requires:
A) Synchronization
B) Reactive power compensation
C) Less insulation
D) Converter stations
Ans: D

Q37. Transmission losses are proportional to:
A) V²
B) I²R
C) f²
D) δ²
Ans: B

Q38. Overhead line supports are usually:
A) Steel tubular poles
B) RCC poles
C) Lattice towers
D) All of these
Ans: D

Q39. Power transfer in transmission line is given by:
A) (EV/X) sinδ
B) (EV/X) cosδ
C) (EV/X) tanδ
D) (EV/X) δ
Ans: A

Q40. String efficiency is the ratio of:
A) Total voltage / Disc voltage
B) Disc voltage / Total voltage
C) Maximum disc voltage / Average
D) None
Ans: A

Q41. ACSR conductor consists of:
A) Only aluminium
B) Aluminium with steel core
C) Aluminium with copper core
D) Copper
Ans: B

Q42. High-voltage transmission lines use:
A) Step-up transformer at sending end
B) Step-down transformer at sending end
C) No transformer
D) Autotransformer only
Ans: A

Q43. The transmission efficiency is maximum when:
A) Corona loss = copper loss
B) Copper loss = constant loss
C) Load power factor = unity
D) Sending and receiving voltages are equal
Ans: B

Q44. Ground wires in transmission lines are provided for:
A) Neutral return
B) Lightning protection
C) Load balance
D) Reactive power
Ans: B

Q45. The insulation strength of overhead line is decided by:
A) Lightning overvoltages
B) Switching surges
C) Corona
D) Conductor size
Ans: A

Q46. Surge impedance loading of 400 kV line is approx.:
A) 200 MW
B) 400 MW
C) 600 MW
D) 1000 MW
Ans: D

Q47. For high voltage cables, the dielectric material used is:
A) Paper
B) PVC
C) XLPE
D) Rubber
Ans: C

Q48. The distance between two consecutive supports is called:
A) Span
B) Sag
C) Clearance
D) String
Ans: A

Q49. Which of the following reduces transmission losses most effectively?
A) Low voltage operation
B) High voltage operation
C) High current
D) Short circuiting
Ans: B

Q50. The inductive reactance of a transmission line is proportional to:
A) Frequency
B) Voltage
C) Current
D) Temperature
Ans: A