Corona and Sag Calculations — MCQs – EE

1. Corona in transmission lines occurs due to:
(A) High current flow
(B) High voltage causing ionization of air
(C) Low frequency
(D) High resistance

2. Corona discharge appears as:
(A) Bright white light
(B) Bluish or violet glow
(C) Red spark
(D) Green arc

3. Which factor most affects corona inception voltage?
(A) Conductor material
(B) Air density and conductor surface condition
(C) Frequency
(D) Line current

4. Corona loss is more in:
(A) DC lines
(B) AC lines
(C) Underground cables
(D) Insulated lines

5. The disruptive critical voltage is the voltage at which:
(A) Corona starts
(B) Conductor melts
(C) Power loss becomes maximum
(D) Air breaks down completely

6. Visual critical voltage is:
(A) Higher than disruptive critical voltage
(B) Lower than disruptive critical voltage
(C) Same as disruptive voltage
(D) Independent of conductor condition

7. Corona loss increases with:
(A) Increase in frequency
(B) Decrease in frequency
(C) Increase in voltage
(D) Both (A) and (C)

8. The empirical formula for corona loss (Peek’s formula) is based on:
(A) Voltage, frequency, and air density
(B) Resistance and inductance
(C) Temperature only
(D) Capacitance only

9. The corona effect can be reduced by:
(A) Decreasing conductor size
(B) Using smooth and larger conductors
(C) Increasing line frequency
(D) Increasing humidity

10. Bundled conductors are used in EHV lines to:
(A) Increase corona
(B) Reduce corona loss and reactance
(C) Increase sag
(D) Reduce line resistance

11. Humidity affects corona by:
(A) Increasing corona loss
(B) Reducing corona loss
(C) No effect
(D) Increasing voltage regulation

12. Corona results in:
(A) Power loss and radio interference
(B) Power gain
(C) Reduced efficiency and improved voltage
(D) Higher insulation strength

13. The value of disruptive critical voltage increases when:
(A) Air density increases
(B) Conductor surface becomes rough
(C) Line voltage decreases
(D) Frequency increases

14. Which of the following reduces the corona effect?
(A) Reducing spacing between conductors
(B) Increasing spacing between conductors
(C) Using rough conductors
(D) Increasing humidity

15. Corona is more pronounced in:
(A) High-voltage and low-pressure conditions
(B) Low-voltage and high-pressure conditions
(C) DC systems
(D) Underground cables

16. The effect of corona is negligible for lines operating below:
(A) 11 kV
(B) 33 kV
(C) 66 kV
(D) 132 kV

17. The spacing between conductors has what effect on corona inception voltage?
(A) Inversely proportional
(B) Directly proportional
(C) Independent
(D) None of these

18. Sag in overhead transmission lines is:
(A) The difference in level between supports and the lowest point of conductor
(B) The length of the conductor
(C) The height of the tower
(D) None of these

19. Sag is directly proportional to:
(A) Conductor weight and span length
(B) Conductor tension
(C) Span only
(D) Temperature only

20. Sag is inversely proportional to:
(A) Conductor weight
(B) Span length
(C) Tension in the conductor
(D) Temperature

21. When wind pressure acts horizontally on conductors, the resultant sag is:
(A) Greater than normal sag
(B) Less than normal sag
(C) Same as normal sag
(D) Zero

22. Ice loading on a conductor causes:
(A) Increase in sag
(B) Decrease in sag
(C) No change
(D) Increases tension only

23. The lowest point of sag in level supports is:
(A) Midpoint of the span
(B) Near the tower
(C) End of the span
(D) Depends on load

24. For unequal supports, the lowest point of the conductor lies:
(A) Exactly at midpoint
(B) Closer to the lower support
(C) Closer to the higher support
(D) None of these

25. The tension in a conductor is maximum at:
(A) The lowest point of the span
(B) The supports
(C) The midpoint
(D) Everywhere same

26. The effect of temperature rise on sag is:
(A) Increases sag
(B) Decreases sag
(C) No effect
(D) Reduces tension

27. To maintain safe clearance, sag should be:
(A) Maximum possible
(B) Minimum within limits
(C) Zero
(D) Infinite

28. The effective weight of a conductor increases due to:
(A) Wind and ice loading
(B) Reduced temperature
(C) Increased tension
(D) None of these

29. The main purpose of providing sag in transmission lines is to:
(A) Avoid mechanical stress and allow expansion
(B) Reduce voltage drop
(C) Improve efficiency
(D) Reduce corona

30. In hilly areas, sag in transmission lines is adjusted to:
(A) Maintain ground clearance
(B) Reduce tower height
(C) Increase power transfer
(D) Decrease line losses