## Power loss due to corona

When corona occurs between two parallel lines of an overhead transmission line, energy is dissipated in form of light, heat, sound and chemical action. After exceeding the disruptive voltage, the power loss due to corona is given by

$$P=242.2(\frac { f+25 }{ δ } )\sqrt { \frac { r }{ d } \quad } { (V-Vc }^{ 2 })\quad X\quad { 10 }^{-5 }\quad$$ KW/Km/PH.

Where, f = frequency in Hz.
V =Rms phase voltage,
Vc = Rms disruptive voltage per phase.

Wireless signals like A.M broadcasting, carrier signal etc, are adversely affected by corona discharges. It may create interference to communication line within even few kilometers. When system voltage becomes high, corona interference also increases. It also depends on conductor surfaces and diameter. Smooth conductor has lower interference.

The radio interference created by transmission line varies inversely with the radio frequency. Hence, high frequency transmission like, T.V, microwave, F.M broad casting are less affected.

► The diameter of the conductor increases due to corona formation. The conducting air surrounding the conductor, increases virtual diameter which reduces electrostatic stresses between the conductors.
► It reduces the effect of indirect lightning. The loss of induced energy in the form of corona, save the conductor from lightning.