Why does a humming sound occur in high voltage transmission lines?
The humming sound that you hear from high voltage transmission lines is caused by a phenomenon called corona effect. Corona effect occurs when the electric field around the conductors is so strong that it ionizes the air molecules, creating free electrons and ions.
These charged particles collide with each other and with the conductors, producing sound waves, light, heat, and radio interference.
The intensity of the corona effect depends on the voltage of the lines, the shape and size of the conductors, the weather conditions, and the cleanliness of the surface³.
The corona effect is undesirable because it causes power loss, damage to the conductors, noise pollution, and interference with communication systems.
To reduce the corona effect, engineers use smooth and large conductors, corona rings, and proper spacing between the lines.
Corona rings are metal rings attached to the ends of insulators that distribute the electric field more evenly and lower its intensity¹².I hope this answer helps you understand why high voltage transmission lines hum.