Top 5 Factors Affecting Corona in Transmission Lines

Corona effect is defined as the phenomenon of a violet glow, which has hissing noise and produces ozone gas in an overhead transmission line.  The corona effect in transmission lines depends on the condition of the power transmission line as well as the atmosphere around the conductors of transmission lines. Given below are top 5 factors upon which corona depends:

Atmospheric conditions

Since the corona is formed due to the ionization of air surrounding the conductors, the physical state and condition of the atmosphere affect corona formation. In stormy conditions, a greater number of ions is present as compared to normal atmospheric conditions. As a result, corona occurs at much less voltage as compared to fair weather.

Conductor Shape and Formation

The conductor shape and formation are major factors that govern the corona formation.

In case of the rough and irregular surface of the conductor, the corona is more likely expected to occur, that is because of the unevenness of the surface which decreases the value of breakdown voltage. Power transmission lines use a stranded conductor rather of solid wire. As compared to a smooth conductor, a stranded conductor has an irregular surface and hence it gives rise to more corona than a smooth solid conductor.

Spacing between conductors

Corona formation also depends on the spacing between conductors. If the spacing between conductors is small then the corona effect is more likely to occur. However, if the spacing between the conductors is made very large as compared to their diameters then, either no corona effect or less corona effect will take place. This happens because the larger distance between conductors reduces the electro-static stresses at the conductor surface thereby avoiding corona formation.

Air density

One important related to corona formation is the critical disruptive voltage: which is defined as the minimum phase-neutral voltage at which corona forms. The corona losses are inversely proportional to the air density factor.

Transmission and Distribution Line voltages

The line voltage at which transmission and distribution lines carry power greatly affects the corona. If the transmission line voltage is low, a corona is not formed since there is no change in the condition of the air surrounding the conductor. However, if the line voltage exceeds the specified voltage value such that electrostatic stresses developed at the conductor surface make the air around the conductor conducting, then the corona effect begins to propagate.

So that was all about the factors that affect the formation of corona in transmission lines.

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