Why high-voltage power transmission lines create noise? Science behind it...

Every time you go near a high-voltage power transmission line you might have observed that it creates a zizzling sound. Ever wondered why?

There is a simple physics behind it. It is electrostatic discharge which causes the noise from that power grid carrying very high-voltage power to various places.

Before explaining how it happens let me introduce a term breakdown strength. It is the minimum field intensity necessary to start a flow of an electric current in an insulator or we can say that to make an insulator behave like a conductor.

In this case the electrical field strength of current carrying wire is greater than that of air surrounding the wire which causes the air near to that to conduct but only up-to a small distance.

This discharge is also responsible for radio noise and corona loss (an energy loss where a visible glow light can be observed near the conductor).

The extent of corona loss and the noise is affected by various environmental parameters like wind, fog, humidity etc.

Conductivity increases in presence of water, so humid and foggy weather increases the corona loss and noise.

Physical condition of wire also affects them. Losses are more at sharp and edge points.

These losses decreases the efficiency in power transmission and now it has became a topic of concern for the power distribution companies. Now the power transmission lines are designed in such a manner that the corona loss is very less.