Why do electrical wires buzz

The intensity of the corona loss discharge is determined by the condition of the air around it. Water increases conductivity.

So when air is humid, or when rain, wind and fog are present, the audible humming from the lines can increase. Irregularities on the conductor surface can also increase the activity. This phenomenon can also affect electrical components within substations. But the public should not be alarmed. Engineers have a found a way to address the issue. They build and maintain high-voltage power lines in such a way that during dry conditions the lines operate below the voltage that will create the corona effect.

This means the line will generate a minimum amount of corona-related noise. But when wet weather occurs, the corona effect can still occur, just not as severe as it would without the precautions. Besides giving off noise, corona causes power loss on the lines and can cause damage to components over time. Utilities install corona rings to combat the effect.

The rings have smooth, round surfaces designed to distribute the electrical charge across a wider area. This then reduces the electrical field and the resulting corona discharges.

The sound of corona is actually the air around the equipment breaking down electrically, or "ionizing". Armstrong says to visualize it as tiny sparks forming a halo or an aura around the equipment. And larger transmission lines, such as kilovolt lines, do generate more corona and louder buzzing when the weather turns wet.

But since corona is usually limited except in certain weather conditions, and especially in cases where power lines are located near significant sources of light pollution, don't expect to see power lines glowing.

And when it's not wet outside, you won't be hearing too much from transmission lines either, according to Armstrong. BC Hydro designs overhead transmission lines to be quiet in ideal weather conditions, and the voltage of distribution lines is generally too low to generate any noticeable corona. While engineers like Armstrong can't do anything about the weather, they do work to keep power lines quiet when the weather is good.

Robert Dent, president of the IEEE Power Engineering Society, responds: "The audible noise emitted from high-voltage lines is caused by the discharge of energy that occurs when the electrical field strength on the conductor surface is greater than the 'breakdown strength' the field intensity necessary to start a flow of electric current of the air surrounding the conductor.

Get smart. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Create Account See Subscription Options.