Concept of Corona
Corona: When a normal alternating voltage is applied across two conductors with enough sparing in between them,then there is no change in atmospheric conditions. But if the voltage applied exceeds a particular limiting value then the air surrounding the conductor gets ionised due to which hissing noise or a faint glow appears. Thus, the phenomenon of hissing noise, faint glow and production of ozone gas surrounding the overhead lines, due to ionisation of air is called Corona. The complete disruption in dielectric strength or insulation of an insulating material (air) near the surface of the conductor at certain point is called concept of Corona. Corona occurs only when the electric field intensity is greater than dielectric strength of air. Fig. Corona Effect In general Corona occurs around the power conductor due to two reasons: I.) Electrical power transmission is at higher operating voltage. II.) Number of free electrons in the space surrounding the power conductor are more due to ...