High THDv% at Residential

[Townshend]

I am having an issue at my residence where there is significant harmonic distortion and I believe the cause of my UPS constantly alternating between battery and line power. The issue has occurred ever since we moved into our house back in March although has been progressively worse the past month and a half. Through monitoring of both the UPS and a Fluke 179 I noted voltage and frequency were all within spec and could not determine any anomalies. My utility company even put in a recorder to monitor at the meter and did not see any anomalies over a 3-4 week period either (as far as I can tell it was just measuring voltage and load).

I then came across harmonics and began to dig into that. I went around my house and at the outlet (dedicated 20A circuit that was recently run) to the UPS I measured THDv% between 9.1-11.4%. I went downstairs to my breaker panel, turned off the master switch, and still measured 11.1% prior to the switch:

The third harmonic seems to have the significant amount of distortion when I go through the first 25 harmonics. This morning, I measured and at THDv 9.8% I have the following:
h01 - 100%
h02 - 0.0%
h03 - 9.7%
h04 - 0.0%
h05 - 1.8%
h06 - 0.0%
h07 - 0.4%
h08-25 - 0.0%

As far as the UPS is concerned, I've taken it and run it for 15 minutes at a couple neighborhood homes (within a 3 mile radius as the crow flies) and a couple commercial buildings. The two other neighborhood homes that, like mine, have a single phase feed also exhibited issues. Similarly, when I measured THDv at one of them it was also in the 9s. The Starbucks down the road the UPS was on line power the entire time and THDv there was 2.6%. That is fed by a three phase padmount transformer.

1. Are there any further data points or tests I can do to narrow down what the issue is?
2. Any tips of getting someone from my utility that has knowledge of harmonics to assist in investigating?
3. If unsuccessful at getting to the root cause, is there any way to mitigate the high THDv% I'm seeing (eg filter etc), that is realistic from a practical and cost perspective for residential?

Thank You!

 

[hbiss]

How about just getting another UPS from another manufacturer?

-Hal

 

[Townshend]

How about just getting another UPS from another manufacturer?

-Hal

Not really interested in going that route as my intent would be to resolve the issue of the high harmonic distortion throughout my house.

 

[tom baker]

What are your utilities limits on harmonics?
There is little we can do to assist you.

 

[tom baker]

What make model UPS do you have? How old is the battery?
Have you tried the ups on a different circuit?
Please post voltage readings

 

[Townshend]

What are your utilities limits on harmonics?
There is little we can do to assist you.

This is where my knowledge seems limited but I would assume they would follow IEEE 519 guidelines which AFAIK is <5% THDv% and <3% for any individual harmonic.

 

[Townshend]

What make model UPS do you have? How old is the battery?
Have you tried the ups on a different circuit?
Please post voltage readings

Wattbox 1100VA. Battery is only a month old maybe? I'm on my 3rd one in 6 months as at the time I had not delved into harmonics to narrow the scope of the issue. Since the THDv% is high on the leg prior to the master switch I am nearly 100% certain that is what is causing the UPS to frequently activate into battery. The circuit (20A) was actually freshly run though and dedicated to the UPS. I have tried other circuits around the house with no success.

I have taken to a couple commercial sites that are fed by a 3ph padmount xfmr with THDv% <3%, easily in the 2s which seems to be where it should be as normal operation, and it didn't flip over ever (multiple 15 minute tests).

Biggest question right now is navigating what equipment and the best point of contact to be able to have my utility company take measurements at the PCC.

Secondarily if the data points above have been seen by others that can help point to a potential reason for the high harmonics (esp the patterns at the individual level or if it's just not enough data to make any educated guess).

Lastly, if the THDv issue isn't and can't be resolved if there is a way to mitigate for my residence, or at least the 20A circuit, will meet the IEEE 519 guideline.

 

[synchro]

Here's a plot of the effect of having a 9.7% third harmonic level with a polarity that reinforces the peak, and also the opposite polarity that flattens the peak. It's also possible to have the third harmonic phase shifted such that there is asymmetry in the waveform. The fundamental content is the same in these plots, but the waveforms of course could be scaled to keep peak level the same, RMS the same, etc.
You might look at your line voltage with a 'scope if you have one available.

There is no real reason that a UPS could not work effectively with this level of harmonic distortion, but I have no idea what your UPS requires.

 

[tom baker]

This is where my knowledge seems limited but I would assume they would follow IEEE 519 guidelines which AFAIK is <5% THDv% and <3% for any individual harmonic.

You can’t assume you need to ask.
Turn off all circuits in the house except for the UPS. if you still shown high THD, then it’s a POCO issue

 

[Townshend]

Here's a plot of the effect of having a 9.7% third harmonic level with a polarity that reinforces the peak, and also the opposite polarity that flattens the peak. It's also possible to have the third harmonic phase shifted such that there is asymmetry in the waveform. The fundamental content is the same in these plots, but the waveforms of course could be scaled to keep peak level the same, RMS the same, etc.
You might look at your line voltage with a 'scope if you have one available.

There is no real reason that a UPS could not work effectively with this level of harmonic distortion, but I have no idea what your UPS requires.

View attachment 2562765

Unfortunately, neither do I yet though I've asked the manufacturer. I have noted that on the rare occasion THDv% is measured at 8.9% the UPS is more stable (though will fluctuate every several minutes or 15 minutes or so). When it gets into the 9s and higher it's a near constant alternation. When on the test sites with <3% THDv, it had no issues.

I forgot to answer the post above, I have monitored voltage by watching a Fluke 179 and the UPS itself keeps a running log of both voltage and frequency. Nothing was out of accepted range, voltage measured maybe 119-123V while frequency measured 59.89Hz at the lowest to 60.00Hz.

 

[don_resqcapt19]

This is where my knowledge seems limited but I would assume they would follow IEEE 519 guidelines which AFAIK is <5% THDv% and <3% for any individual harmonic.

Most harmonic issues originate with the utility customers and not the utility itself. Your utility may have rules that limit the harmonics that a customer can create in their distribution system that are not being enforced.
Are there customers in your area that may be introducing harmonics into the distribution system?

 

[Townshend]

Most harmonic issues originate with the utility customers and not the utility itself. Your utility may have rules that limit the harmonics that a customer can create in their distribution system that are not being enforced.
Are there customers in your area that may be introducing harmonics into the distribution system?

The only significant elements I've noticed in a few block radius are a few houses with solar panels. Could that introduce that significant of a THDi% to get THDv% to this sort of level though?

FWIW this isn't sporadic where residential generator would be a likely cause either. For approximately 6 weeks straight I get consistent 9-11% THDv%. Even right now on a dry day with 57°F temps at 11:30p I am reading 9.8% THDv. I've read where HVAC and sump pumps can introduce harmonic distortion but those usages should be minimal to non-existent with neighbors right now.

 

[Townshend]

You can’t assume you need to ask.
Turn off all circuits in the house except for the UPS. if you still shown high THD, then it’s a POCO issue

Good point and agreed. That circles back to my 2nd question, who to actually talk to at the power company. I've had a ticket open since 10/18 but unfortunately any points of contact have little to no knowledge of harmonics.

I have measured both with all circuits except the 20A UPS one and even with all circuits (master) off and still a high THDv%. The only place I have not ruled out completely yet is from the PCC to the breaker panel, I haven't found a way to access and hoping the utility (ComEd) will come with a PQM that can measure and an engineer who can read at the PCC and if so, at the transformer.

 

[junkhound]

Take a scope pic of your CURRENT waveform, and the voltage, and post that. Can sometimes tell from that which neighv=borhood loads are the culprit.
My guess is that someone (or you) have a cheap inverter on something running -akak cheap means simple diode rectifier in front end. examples are cheap bitcoin miners, induction cooktops, some washing machines, etc.

The EU has consumer electronics power factor and harmonics specifications, USA does not.

Company 'upgraded' a few hundred computers in the 1990s, new computers had simple rectifier bridge front ends, triplet harmonics overheated and blew the poco delta-wye transfomrers.

 

[ptonsparky]

Are the area residences fed single phase from a 3 phase secondary? What is the L-L voltage?
208 to single family homes would be an odd duck here.

 

[Jpflex]

Here's a plot of the effect of having a 9.7% third harmonic level with a polarity that reinforces the peak, and also the opposite polarity that flattens the peak. It's also possible to have the third harmonic phase shifted such that there is asymmetry in the waveform. The fundamental content is the same in these plots, but the waveforms of course could be scaled to keep peak level the same, RMS the same, etc.
You might look at your line voltage with a 'scope if you have one available.

There is no real reason that a UPS could not work effectively with this level of harmonic distortion, but I have no idea what your UPS requires.

View attachment 2562765

Where can I learn more about harmonic current/ voltage. The course I took did not go into detail on this subject as I expect this to be an advanced level area.

From what I know typically Some non linear loads such as computers distort current/voltage ? Waveform shifting similar to power factor shifting in inductive reactive or capacitive reactive loads and does this on specific cycles? My understanding is limited at this point, but what effect does harmonics have On circuits? Thanks