Corona Effect MCQ

1. Corona effect can be identified by

1. arcing between conductors and earth
2. red light
3. faint violet glow
4. bushy sparks

2. Corona losses in DC transmission is

1. minimum
2. high
3. infinite
4. extra high

3. Corona discharge is generally _______ in colour:

1. blackish
2. bluish
3. yellowish
4. brownish

4. What is the effect of critical voltage for corona in case of bundle conductors compared with single conductor?

1. remain same
2. decrease
3. increase
4. not occur

5. The corona loss on a particular system at 50 Hz is 1 kW/Km/phase. What is the corona loss at 60 Hz in kW/Km/phase?

1. 0.83
2. 1
3. 1.13
4. 1.2

6. Corona loss in transmission lines are minimized when

1. conductor size is reduced
2. smooth conductor is used
3. sharp points are provided in the line
4. current density in conductor is reduced

7. Which of the following steps is taken in order to reduce corona losses in AC transmission.

1. the gap between the conductors is increased
2. load is increased
3. the gap between the conductors is decreased
4. load is reduced

8. Corona effect in transmission can be detected by

1. hissing sound
2. the faint luminous glow which is blue in colour
3. presence of ozone which is detected by odour

Which of these is/are correct?

1. only 1 and 2
2. only 1 and 3
3. only 2
4. 1, 2 and 3

9. Corona loss is minimum in

1. monopolar HVDC line
2. bipolar HVDC line
3. both in monopolar and bipolar HVDC line
4. EHV AC lines

10. If AC corona losses in a transmission line are 0.6 kW, then for the same line voltage, the approximate value of DC corona loss will be

1. 1800 W
2. 1.2 kW
3. 0.2 kW
4. 0.3 kW

11. Corona loss increases with

1. increase in supply frequency and conductor size
2. increase in supply frequency and reduction in conductor size
3. decrease in supply frequency and conductor size
4. decrease in supply frequency but increase in conductor size

12. The good effect of corona on overhead lines is to

1. increase the line current carrying capacity
2. increase the power factor
3. reduces radio interference
4. reduce the steepness of surge fronts

13. The disruptive critical voltage will

1. decrease with the increase of moisture content in the air
2. increase with the increase of moisture content in the air
3. increase with the decrease of moisture content in the air
4. decrease with the decrease of moisture content in the air

14. Corona occurs between two transmission conductors when they

1. have a high potential difference
2. are closely spaced
3. carry dc power
4. both a and b

15. Corona loss can be reduced by the use of a hollow conductor because

1. the current density is reduced
2. the eddy current in the conductor is eliminated
3. for a given cross-section, the radius of the conductor is increased
4. of better ventilation in the conductor

16. Corona effect can be detected by

1. presence of ozone detected by odour
2. hissing sound
3. the faint luminous glow of bluish colour
4. all of the above