Electric power transmission practically deals with the bulk transfer of electrical energy, from generating stations situated many kilometers away from the main consumption centers or the cities. For this reason the long distance transmission cables are of utmost necessity for effective power transfer, which in-evidently results in huge losses across the system. Minimizing those has been a major challenge for power engineers of late and to do that one should have a clear understanding of the type and nature of losses. The corona effect in power system, has a predominant role in reducing the efficiency of EHV (extra high voltage lines) which we are going to concentrate on, in this article.
When a high or extra high voltage transmitted in a transmission line, due to magnetic effect on the core of the conductor all most all electronics pass on the surface of the conductor. So the air outside the conductor surface became conducive and looks bluish and due to dielectric breakdown of air a hissing noise comes from surrounding, Called as corona !
Due to corona OZONE formation on the outside surface of the conductor. The effect of this to the power system is called as corona effect.
First consider a conductor system to which voltage is applied. If the potential applied is raised, gradually, beyond a limit, a pale violet glow will appear. This will be accompanied by a hissing noise indicating the ionization of surrounding air of the conductor surface with characteristic smell of ozone. This phenomenon is known as corona.
Simply we can say, phenomenon of violet glow, hissing noise and production of ozone gas in an overhead transmission line is known as corona effect.