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Sound of 'crowns': why power lines make more noise in the rain

Image of power lines under black storm clouds

Wet, foggy, or snowy conditions can increase that buzzing sound

Posted by Chelsea Watt

Have you ever noticed a buzzing or crackling sound when you've been near overhead power lines? Did you notice that the sound is more noticeable when it's raining or wet outside (a weather condition that's certainly not in short supply in B.C.'s fall and winter months)?

Well, that sound has a name, according to BC Hydro specialist engineer Mazana Armstrong.

Corona, Latin for crown, is the name for the luminous "crown" of tiny sparks that can, very rarely, be visible around equipment such as power lines and insulators. It's this crown that causes the occasional buzzing and crackling that you can hear.

According to Armstrong, it's rare to actually see the namesake glow along power lines in B.C., but the buzzing sound can be readily apparent in the right conditions.

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.

"Water droplets like rain, snow, or even fog and mist, help speed the electrical breakdown of the air particles, making the corona louder and easier to hear," she says.

And larger transmission lines, such as 500-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.

Transmission lines are meant to be seen, but not heard

Hearing power lines buzz when the weather is fine can actually be a sign that something is wrong, says Armstrong. Increased sounds of buzzing during good weather can indicate equipment isn't performing optimally.

As electricity travels through transmission lines over long distances, there's some power lost because of corona. That makes power lines inefficient. One of the ways that BC Hydro and other utilities work to eliminate inefficiencies is also what helps to reduce buzzing sounds; using rounded shapes for power line hardware and equipment.

As Armstrong explains, sharp and pointed objects initiate corona much more quickly, so utilities tend to use smooth, rounded objects for equipment like insulators.

"Sharp, pointy objects help to initiate corona. The smaller the radius of the object, the more prominent the corona becomes," says Armstrong. "That means energized hardware that is sharp and pointy would be much louder than the rounded, smooth-edged one."

Chelsea Watt is a writer-editor with bchydro.com.