14 % Harmonic Distortion at residential customer 1

[st50maint]

I have some high end audio equipment that displays the distortion of the incoming power.
My incoming power had always been between 2% and 3% distortion. Since a storm 4 weeks ago it has been 14% distortion. I have called LIPA (Long Island Power Authority) twice and have gotten the runaround. It seems that as long as my “appliances” are functioning, they are not interested in one residential customer’s whacky complaint.

2 questions;

1. Do I have the right to expect much lower distortion power from LIPA?
2. If so, any suggestions on how to get their attention?

Here is a picture of the incoming waveform:

 

[davidbeach]

Incoming what waveform? Voltage, current? Certainly not power.

 

[st50maint]

The waveform is of the voltage.

 

[jghrist]

IEEE Std 519, IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems has limits for utilities which generally limit the voltage distortion to 5%. This standard is a recommendation, not a legally binding requirement, but you should try to get the utility to meet its requirements.

The flat top on the voltage waveform could be a result of a large amount of distorted current from switched mode electronic power supplies causing voltage drop through the service transformer. Switched mode power supplies draw current only during the middle of each half wave. Was your transformer replaced in the recent storm? Maybe the replacement has a higher impedance than the original.

 

[rasevskii]

It could be that, after the storm, your neighborhood is now on a different feeder from the LIPA substation than before, or from a different substation. The overhead line distribution system in the USA is flexible in that pole top switching can be done to change customers easily to another source, unlike cabled systems where that is difficult.

If you are near the electrified portions of the LIRR, it can be that harmonics from the silicon rectifiers in the DC substations are appearing, they will however vary with the load current drawn by the trains.

Here in my city in Europe, harmonics from the rectifiers feeding the rail system are clearly hearable at consumers near the grid substations, as well as the variations due to the load changes. Even in fan motors and audio systems.

rasevskii

 

[potteryshard]

It may be that people you contacted just didn't understand the complaint... Usually utilities are pretty aware of and responsive to power quality issues. In a utility that size, I'd guess there are a half dozen people charged with u=investigating PQ isssues. These usually occur with commercial services, and their focus will likely be the same, so it may take a bit more effort for a residential customer to get their attention.

If this was presented as a 'distortion' issue, it likely didn't ring any mental bells for the receptionist, and it didn't wind up in the appropriate pigeon hole. I'd write an e-mail making a power quality complaint. If no response, send a copy to the PUC.

This is probably not creating a problem for you, but may be indicative of an incipent problem on their system.

 

[rbulsara]

It depends on what contract, in writing, do you have with the utility company.

Rafiq Bulsara

http://www.srengineersct.com

 

[magoo2]

As was mentioned before, 5% voltage THD or less would be normal per IEEE Std 519.

How much current were you pulling with your high end audio equipment when you recorded this unscaled voltage waveform?

In calling LIPA again, I would reference this as a PQ issue. The PQ folks deal more with harmonics and voltage distortion and should be able to check it out.

 

[stevencress]

Chances are the problem is in your house. If you have a battery powered portable radio, turn it on and see if you hear loud buzzing noise at the low end of the AM dial, then check the high end of the AM dial. Nothing? Carry the radio to various rooms and see if you can detect the LOUD BUZZING noise. Nothing? Then the noise is probably coming from the power company or one of your neighbors.

If you do hear the buzzing, turn off the main circuit breaker in your breaker panel in your house. If buzzing continues with main breaker off, problem is from the power company. If buzzing stops when you open the main breaker, close the main breaker, and open the other breakers one at a time until the buzzing ends. The breaker that is turned off when the noise ends is the problelm breaker. Turn that breaker back on and go to the area in the house fed by that breaker, and unplug or turn off each electric device fed from that suspect breaker. If you unplug a lamp and the buzzing stops, the lamp probably has a bad dimmer. If the problem is in the garage, it might be the door opener. It might be a computer document scanner, or a new refrigerator, or an Obama light bulb.

 

[Skogsgurra]

This is clearly an LF harmonics issue and that will not be noticed on AM. Not even in the long-wave band, where frequencies are in the 100 - 300 kHz range as compared to the 180 - 3000 Hz range produced by these LF harmonics.

But not good and there may be a transformer running hotter than expected when voltage looks like this. Contact the utility PQ people. They should react to this.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[st50maint]

When the scope photo was taken, the audio equipment was shut off. The only items drawing significant current were incandescent light bulbs and the vacuum tube oscilloscope itself.

The problem is not only in my house. I borrowed test equipment from work and tested my neighbor’s house. I measured the same 14% distortion. I went to a delicatessen about 1/5 mile away and same problem. I then went to my mechanic about 1 mile away and his distortion was good at only 3%.

 

[st50maint]

The problem has been corrected by LIPA. Distortion now measures 2.6%. Thanks for the help.

 

[itsmoked]

LIPA = Lime Infused Pear Anchovies?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Keith,

Refer to the first post!

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If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

Thanks Scotty.

So it was the delivered power and they fixed it. Nice.
And nice sleuthing st50maint.

st50maint; Did they happen to tell you what they did to fix it?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[st50maint]

No, LIPA did not tell me anything about the fix.

 

[st50maint]

After 4 good months the problem has returned. I have had 14% distortion for the last 10 days. I am not looking forward to calling customer service. If any new readers of this old thread have any suggestions, they will be greatly appreciated.

 

[st50maint]

The first post was not formatted properly to show the picture. Here it is now.

 

[Miguel Villarroel]

Do you have your own grounding systems at home?

If there was no electricity there would be no internet. Good point, don´t you?

 

[Skogsgurra]

Even more flattened now. Looks like more SMPS have been added. But the transients at the end of the flattening seem to be gone.

Has the buzzing sound returned? I guess not.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.