this is strange

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rt66electric said:
Ask him if there are any bumble/honey bee nesting inside the walls.. A infared camera will locate a bee's nest inside of a wall. The temperature of nest will be warmer/cooler than ambient..
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Even though I have never heard the noise, I don't believe this to be the case. But I could be wrong!

Brian Oshman said:
Are there radon fans mounted on the wall outside the panel making a mechanical vibration and when the right breaker is cut off they obviously lose power?
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The noise does not go away with turning off any one breaker. The customer has reported the noise reducing when turning off breakers in succession.

wireguru said:
does your customer have a neighbor who likes to weld? (possibly coupled with a loose neutral somewhere)
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Possibly:grin:. I think this is coming from the utility lines.

Besoeker said:
If you look at the noise on the waveform, it appears to be identical from one cycle to the next. I would have expected arcing to ground to show a more random disturbance. If you did have arcing to ground wouldn't that eventually cause a failure if it was allowed to persist undetected?

The noise on the waveform looks sort of similar to some I have seen on supplies that feed three-phase SCR based DC drives where you get notching and sometimes ringing at 60deg intervals. What your customer's supply sees could be an attenuated version of that. And given that it would have a repetition rate of 360Hz, it would certainly be in the audible range.

Just a few thoughts FWIW
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Good point about it being uniform arcing. I suppose it would be random if it was what I thought. Maybe a load causing this is more probable than I thought.

Ragin Cajun said:
Any VFD drives on HVAC equipment? Even some of the small ones have them now.
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I don't believe it is the customer's load causing the noise.

beanland said:
There appear to be three sets of "noise" on the 60Hz waveform. That tells me this migh tbe a 3-phase issue. Is the customer close to a substation? Some AMR (automated meter reading) equipment use a large transformer (225kVA) in the substation to impose a carrier wave on the 60Hz in order to talk to and receive meter readings from household electric revenue meters. If this signal is strong enough, it could be causing magnetic items in the house (motor, ballast) to convert this power line carrier signal to audible noise.

If this is a power line carrier for AMR, contact the utility. What might be needed is a capacitive noise filter at the main panel and the POCO should pay for it!

If it is not AMR PLC, then some other 3-phase device (large VFD?) might be the cause. Because the noise is not constant, that tells me there is a process running periodically, not continuusly.
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I am the utility.:grin:. We do not have the AMR capability installed on this circuit, but are in the process of getting the infrastructure installed on other circuits.

Excellent point on it being three phase possibility given the points on each cycle that the noise is showing up.

Since the customer is not complaining about this anymore, I am going to set this one on the back burner. I have suspicions that this is load related, possibly from a steel mill, but that steel mill is electrically very far away, but geographically close (if that makes any sense). When the customer reported the buzzing was much less frequent and was quieter, was the same time the steel industry was starting to fall off. If the noise starts back up, I think I will monitor at the substation 12 kV bus to see if I see the noise there too.

Thanks everyone!:smile: By the way, the multi-quote function on this site is awesome!
 
Does your customer wear hearing aids?? Do you hear the buzzing? Don't laugh. I went thru this with an older lady for weeks in a retirement home. She would call and I would go have a look. She could hear it but I could not. I happened to be standing close one time and I heard it but it was not from the panel, it was from her hearing aids! Something in the panel caused it. I didn't bother to find out what. I now wear hearing aids and find the problem from time to time but just ignore it. I don't have much occasion to walk near a panel anymore.
 
Anthony Cox said:
Buzzing coming from an electical panel?

Sounds like an arc to me.

I would check every connection in that panel for signs of arcing.
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The customer reports hearing the buzzing from his plasma TV, flourescent lighting, plug in power supplies (AC-DC) and occasionally his ceiling fan. There is also some buzzing in the panel as well, but that is not what was troubling him.
 
Do you have the current waveform? It may help determine if the problem is upline or downline. Do you have some waveforms from a different time period?

I would think if it were far upline, others would have found issues as well.

Since you are the POCO it would be easy for you to monitor a second customer on the same service, and third on the same feeder but different service, and a forth on the same substation but different feeder (or the sub bus).

If it is a problem on your feeder/service it would be good to know and probably should be moved from the back burner. Power quality is important to the POCO, and is one criteria used to justify your rates.

As Besoeker pointed out, it does not appear to be random arcing.
 
I was working in a 240V 3 phase panel last week (the same one that I posted about earlier).

This building has 3 service panels sitting side by side and all are fed from a common trough that's mounted under the panels.

The center of the three is where all of the breakers for the building HVAC are located.

While I was in a adjacent panel, the center panel began to buzz.
I knew immediately that the AC had come on, the buzz was clearly 60Hz.
I knew this the same way that most on this site would, from being around 60Hz power for a long time.....you just know it when you hear it.

I pressed on the panel cover, and the screws were not tight.
The buzzing was coming from the cover vibrating against the enclosure.

I tightened the screws, and the noise went away.

Look for the simple things first.

steve
 
I had a simular problem that went on for a year or more. I would hear buzzing on my radios and TV. The SAT Receiver itself would buzz. My L-L voltage was about 250VAC. No pattern could be detected. Turned out that my private distribution transformer's windings were shorting out, causing the voltage rise. The arcing may be coming from the transformer. It finally went out with a bang ! The Power Company had to replace the transformer & TV.
 
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