MCQs of Corona

Showing 1 to 10 out of 47 Questions
1.
Corona loss is less when the shape of the conductor is
 (a) Circular (b) Flat (c) Oval (d) Independent of shape
2.
Corona loss increases with
 (a) Increase in supply frequency and conductor size (b) Increase in supply frequency but reduction in conductor size (c) Decrease in supply frequency and conductor size (d) Decrease in supply frequency but increase in conductor size
3.
The corona loss on a particular system at 50Hz is 1 kW∕ phase ∕ km. The corona loss on the same system with supply frequency 25 Hz will be
 (a) 1 kW ∕ phase∕ km (b) 0.5 kW ∕ phase∕ km (c) 0.667 kW ∕ phase ∕ km (d) None of the above
4.
In EHV transmission lines, efficiency of transmission can be increased by decreasing the corona loss. This is achieved by
 (a) Increasing the distance between the line conductors (b) Using bundled conductors (c) Using thick conductors (d) Using thin conductors
5.
Which of the following statements regarding corona are true?
2. It attenuates lightning surges
3. It amplifies switching surges
4. It causes power loss
5. It is more prevalent in the middle conductor of a transmission line employing a flat conductor configuration.
 (a) 1, 3 and 5 (b) 2, 3 and 4 (c) 1, 2, 4 and 5 (d) 2, 3, 4 and 5
6.
Corona loss can be reduced by the use of hollow conductor, because
 (a) Current density is reduced (b) Eddy-current in the conductor is eliminated (c) For a given cross-section, the radius of the conductor is increased (d) Of better ventilation in the conductor
7.
Compared with a solid conductor of the same radius, corona appears on a stranded conductor at a lower voltage, because stranding
 (a) Assists ionization (b) Makes the current flow spirally about the axis of the conductor (c) Produces oblique sections to a plane perpendicular to the axis of the conductor (d) Produces surfaces of smaller radius
8.
The charging current in a transmission line increases due to corona effect because corona increases
 (a) Line current (b) Effective line voltage (c) Power loss in lines (d) Effective conductor diameter
9.
Hollow conductors are used in transmission lines to
 (a) Reduce weight of copper (b) Improve stability (c) Reduce corona (d) Increase power transmission capacity
10.
To increase the visual critical voltage of corona for an overhead line, one solid phase conductor is replaced by a bundle of four smaller conductors per phase, having an aggregate cross-sectional area equal to that of the solid conductor. If the radius of the solid conductor is 40 mm, then the radius of each of the bundle conductors would be
 (a) 10 mm (b) 20 mm (c) 28.2 mm (d) 30 mm
Showing 1 to 10 out of 47 Questions