The phenomenon of corona is affected by the physical state of the atmosphere as well as by the conditions of the line. The following are the factors upon which corona depends :
As corona is formed due to ionsiation of air surrounding the conductors, there-fore, it is affected by the physical state of atmosphere. In the stormy weather, the number of
ions is more than normal and as such corona occurs at much less voltage as compared with
(ii) Conductor size
The corona effect depends upon the shape and conditions of the conductors. The rough and irregular surface will give rise to more corona because unevenness of
the surface decreases the value of breakdown voltage. Thus a stranded conductor has ir-
regular surface and hence gives rise to more corona that a solid conductor.
(iii) Spacing between conductors
If the spacing between the conductors is made very large as
compared to their diameters, there may not be any corona effect. It is because larger dis-
tance between conductors reduces the electro-static stresses at the conductor surface, thus
avoiding corona formation.
(iv) Line voltage
The line voltage greatly affects corona. If it is low, there is no change in the
condition of air surrounding the conductors and hence no corona is formed. However, if the
line voltage has such a value that electrostatic stresses developed at the conductor surface
make the air around the conductor conducting, then corona is formed.
Reference and bibliography: Power System Analysis, By VK Mehata, AK Mehta.