this is strange

Status
Not open for further replies.

wirenut1980

Senior Member
Location
Plainfield, IN
I have a customer who experiences a buzzing noise that he claims comes from his electrical panel, all CFL lights, all wall wart transformers, and his plasma TV.

He says he has tried turning off circuit breakers one at a time, and as he does that, the buzzing decreases a little every time. When they are all shut off, the buzzing does stop.

The buzzing happens in late afternoon and at different times at night. Sometimes it happens multiple times a day, sometimes it will go a week without happening. I have been there a couple times to set and download a monitor at the main service and the buzzing did not occur while I was there.

After I set the monitor, he says the buzzing intensity has been cut in half and it happens a lot less frequently and for shorter periods of time. While monitoring, I had him take down the times he heard the buzzing, so I could compare with the data.

When the buzzing occured, there was no change of voltage or current in the data. Everything looks hunky dorry with the data.

I am stumped on what to do next. I feel like he might have something loose in his main panel, but I don't think that explains the noise coming from the other things mentioned.

RFI could explain the plasma TV buzzing noise...but the only way that makes sense is if the RFI is coming from the loose connection in the panel. Is that possible?

The only problem with that theory is that I did not think that wall warts and CFL's would buzz as a result of RFI or a loose connection at the panel.

Any suggestions on what to look for next would be appreciated.:-?

Thanks!:D
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
I don't know if it is the cfl's but my guess is that the cfl's are not the problem. Sounds like a breaker needs replacing. Some will buzz when they are under a load.

If you think it is the cfl's then replace them with incandescents and see if it makes a difference.
 

Besoeker

Senior Member
Location
UK
I don't know if it is the cfl's but my guess is that the cfl's are not the problem..
I'm inclined to agree. CFLs generally have an electronic ballast operating at some tens of kHz.
Even if audible, it wouldn't be described as a buzzing sound.
60Hz would.
 

wbalsam1

Senior Member
Location
Upper Jay, NY
a 60 cycle hum creates the music pitch "B". I often tune my 5-string banjo's 2nd string to the pitch I hear from my flourescent lights...saves me using my electronic tuner.
Perhaps there's a vibration going on within the building that needs dampening somehow. Just a thought. ;)
 

hillwack

Member
is it a constant buzz when it happens or is it a cell phone RFI. to test it just put a cell phone next to a speeker and call it, his cell would be best to test with. other then that i would say find the source of the sound but i guess you have to hear it first.
 

wirenut1980

Senior Member
Location
Plainfield, IN
My money is on nearby industry. Induction furnaces, maybe? Zillion horsepower rock crushers?
I had thought about that too. There is a large steel mill about 10 miles away, but electrically, it is very far away - it is fed at 345 KV. But it is possible. If nobody else has a plasma TV or CFL lights, they might not notice anything. This is possible as the customer lives in a rural area. If the steel plant is the cause, is it some kind of resonance, or very high frequency voltage fluctuations? My monitor takes a sample every 65 micro-seconds, but I wonder the fluctuations are small, high frequency, so as not to be noticed in the lights...hmmm.

The incandescants do not buzz, so I did make some kind of connection that every load that buzzes seems to have some high frequency switching.

I think the most likely explanation is a loose connection...maybe on the main breaker. But has anyone every heard of that causing buzzing in electrical loads?

480 sparky interpreted my slang correctly. Plug in AC-DC transformers.:D

Thanks for the suggestions, keep up the discussion!:)
 

Besoeker

Senior Member
Location
UK
I had thought about that too. There is a large steel mill about 10 miles away, but electrically, it is very far away - it is fed at 345 KV. But it is possible. If nobody else has a plasma TV or CFL lights, they might not notice anything. This is possible as the customer lives in a rural area. If the steel plant is the cause, is it some kind of resonance, or very high frequency voltage fluctuations? My monitor takes a sample every 65 micro-seconds, but I wonder the fluctuations are small, high frequency, so as not to be noticed in the lights...hmmm.
Have you tried looking at the voltage waveform with an oscilloscope?
 

wirenut1980

Senior Member
Location
Plainfield, IN
Have you tried looking at the voltage waveform with an oscilloscope?
I did not capture a waveform while the buzzing was occurring. I had set the monitor to capture a waveform, triggering on sags and swells, and voltage THD 5% or greater.

My allotted waveforms filled up in the first day of monitoring on voltage THD trigger being exceeded. But when I looked at the waveforms, the voltage THD was never greater than 3%. I am working with the manufacturer to determine why this happened. I am still monitoring in hopes of capturing a waveform during the buzzing period. I'll keep you all posted on what I find out. I am stumped so far.
 

Besoeker

Senior Member
Location
UK
I did not capture a waveform while the buzzing was occurring. I had set the monitor to capture a waveform, triggering on sags and swells, and voltage THD 5% or greater.

My allotted waveforms filled up in the first day of monitoring on voltage THD trigger being exceeded. But when I looked at the waveforms, the voltage THD was never greater than 3%. I am working with the manufacturer to determine why this happened. I am still monitoring in hopes of capturing a waveform during the buzzing period. I'll keep you all posted on what I find out. I am stumped so far.
Thanks, Wirenut.
Can you capture and download numerical data to a spreadsheet or a table?
 

wirenut1980

Senior Member
Location
Plainfield, IN
In case anyone is still interested, I did eventualy capture some waveforms during the buzzing. However, the buzzing noise was not as loud as in the past. There is some evidence of arcing. The matter was somewhat unresolved in my mind at least. I noticed that the incoming voltage was a bit high. Some checking around revealed that the substation LTC bandwidth setting was too wide. Fixing that lowered the voltage to within the proper range. After that happened, the customer reported not hearing the buzzing as often, and when he did hear it, it was not nearly as loud and not annoying to him. My best guess from the waveforms and results of lowering the voltage was that there was something (possibly an insulator) on the medium voltage system arcing to ground. Maybe lowering the system voltage was enough to stop or reduce the arcing.

The waveform was captured at the customer's main panel with little customer load on at the time.
 

rt66electric

Senior Member
Location
Oklahoma
Don't overlook the obscure!!

Don't overlook the obscure!!

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..
 

Besoeker

Senior Member
Location
UK
My best guess from the waveforms and results of lowering the voltage was that there was something (possibly an insulator) on the medium voltage system arcing to ground. Maybe lowering the system voltage was enough to stop or reduce the arcing.
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
 

beanland

Senior Member
Location
Vancouver, WA
Power Line Carrier

Power Line Carrier

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.
 
Status
Not open for further replies.
Top