Powerline Hum: What Causes It & How to Stop It

  • Thread starter Flying Penguin
  • Start date
In summary: The hiss of corona discharge modulated at the 120 Hz line rate. It's not 60 Hz because there are two peaks and zero crossings for each cycle.
  • #1
Flying Penguin
22
0
What exactly is the noise?
 
Engineering news on Phys.org
  • #2
I believe it's a low-level corona discharge that can happen with HV power lines, but I'm not sure. It's usually worse when the air is real humid, like in foggy conditions, and the conduction of the air is higher. Kind of like the noise from neon signs. It's not magnetostriction, so it seems like it would have to be associated with the corona discharge from the high voltage at 60/50Hz. Anybody else know for sure?
 
  • #3
The hum is usually a 60-cycle hum, and is probably caused by the physical motion of the wires or metal coverings on transformers, instigated by the changing EM field, exerting a force on the iron/steel. I expect this is acts like a very inefficient speaker.

On powerlines in the air, there is probably a phase difference between powerlines widely spaced or on different circuits causing the air to act like part of a giant electrostatic speaker (in the hearing range).
 
Last edited:
  • #4
Because they don't know the words.
 
  • Haha
Likes Jon Richfield
  • #5
Nam_Sapper said:
The hum is usually a 60-cycle hum, and is probably caused by the physical motion of the wires or metal coverings on transformers, instigated by the changing EM field, exerting a force on the iron/steel. I expect this is acts like a very inefficient speaker.

On powerlines in the air, there is probably a phase difference between powerlines widely spaced or on different circuits causing the air to act like part of a giant electrostatic speaker (in the hearing range).

I think this would not be efficient enough to be audible. The current
in a high-voltage transmission line is low and conductor spacing is large.
Furthermore, the acoustical radiation efficiency of a wire at 60 or 120 Hz
is quite low.

If a 750KV transmission line carried 30 MW, the current would be around
40 Amps. While this kind of current would make conductors slap the walls
of a conduit, they would be separated by maybe 30 meters in the transmission
system. Forces would be very low.

It's the hiss of corona discharge modulated at the 120 Hz line rate. It's
not 60 Hz because there are two peaks and zero crossings for each
cycle.

Edit: If you are in or near a power substation, then you are likely hearing the
magnetic cores of the transformers as they vibrate at 120 Hz. They are typically quite loud.
 
Last edited:
  • #6
Thers another penguin on this board??
 
  • #7
not big enough for 2?
 
  • #8
faust9 said:
Because they don't know the words.
OMG. brilliant quip. How did I miss it?
 

1. What is powerline hum?

Powerline hum is a low-frequency buzzing or humming sound that can be heard in electrical appliances, outlets, or wiring. It is typically caused by electromagnetic interference from power lines.

2. What causes powerline hum?

Powerline hum is caused by the magnetic fields generated by the electric current flowing through power lines. These magnetic fields can interfere with the electrical signals in appliances and cause the buzzing sound.

3. How can I tell if the hum is coming from power lines?

If the hum is present when an appliance is turned on but goes away when it is unplugged, it is likely coming from power lines. You can also try turning off the main power to your home and see if the hum stops. If it does, then it is likely caused by power lines.

4. How can I stop powerline hum?

There are a few ways to stop powerline hum, including using a power conditioner or surge protector, installing a dedicated circuit for your appliances, or using a noise filter. You can also try moving your appliances to a different outlet or using shielded cables to reduce interference.

5. Is powerline hum dangerous?

No, powerline hum is not dangerous. It is simply a nuisance and does not pose any health risks. However, if you notice a sudden increase in the intensity of the hum or if it is accompanied by other electrical issues, it is best to consult a professional electrician to ensure there are no underlying problems with your electrical system.

Similar threads

  • Electrical Engineering
Replies
12
Views
876
  • Electrical Engineering
Replies
3
Views
723
  • Electrical Engineering
Replies
8
Views
2K
  • Electrical Engineering
Replies
14
Views
4K
  • Classical Physics
Replies
4
Views
863
  • Electrical Engineering
Replies
27
Views
1K
  • Electrical Engineering
2
Replies
38
Views
4K
Replies
12
Views
2K
  • Electrical Engineering
Replies
3
Views
1K
Replies
5
Views
2K
Back
Top