Distortion on the Power Line

I have a couple of PS Audio Power Plants.
The distortion off the wall has typically been 3.5 to  4.0.  For the last week it has been over 7%.  I checked around the house and can see no changes.  Anyone have any ideas what it is?  Have Russian Hackers moved in next door?  People huddling at home on their computers?

Neighbor's running air conditioners??
It could be caused by a loose and or corroded electrical connection. It can be anywhere in your home. For the loose and or corroded connection to cause harmonic distortion it needs a load connected to it naturally.

Is the branch circuit the PS power plants are plugged into a dedicated branch circuit strictly for your audio system? Is the branch circuit wiring continuous from the electrical panel to the wall outlet duplex receptacle? No junction boxes?

What is the make, manufacturer, of the electrical panel? Just a guess, how old is it?
For about 2 1/2 man hours of a labor charge ( should cover trip charge) you could hire an electrician to check all the wire terminations in the panel for tightness and for any signs of corrosion. He will also check the connections on the main breaker and service entrance neutral conductor. He also should be able to do a heat thermal check of the breakers and breaker connections to the panel bus. You could have a bad breaker or a poor breaker to bus connection. Those are notorious for arcing on heavily load breakers where the bus is aluminum.

Also have him check the connections on the duplex outlet the PS audio power plants are plugged into.

While he’s there, (for lightning protection), have him check the System Grounding, formally called the Grounding Electrode System, for it’s electrical integrity, and connections for corrosion and tightness. Outside ground rods as well.

I have heard of an old appliance, like and old refrigerator or freezer in the garage or basement that was causing harmonic distortion on the AC mains.

I’ve heard many members on various audio forums say they fought a high level of harmonic distortion on the mains and tried everything they were told to look for that might be causing the distortion. Several guys said it ended being a loose and or corroded conductor lug connection in the meter socket base. Especially if the electrical service is fed overhead. ( rain water follows down the service drop conductors inside the mast conduit and runs onto the line connection lugs. the water causes corrosion. Corrosion can cause minor arcing in the connection, harmonic distortion.)

Any loose and or corroded connection/s anywhere on the electrical service power wiring from the utility pole power transformer connections to >>> the power company’s over head power line to >>> your house’s weather head service drop conductors connections to >>>> to the meter socket base Line lugs connections from >>> the meter socket base load lugs connections to >>> the electrical panel main breaker connections and service neutral conductor to neutral bar connection.. As you can see there are a lot of connections. A minimum of 15 connections. The connections outdoors are the most vulnerable to the elements. For these you will need to call your utility power company. They will, should, also check the connections in the meter socket for corrosion and tightness. FYI in most cases the home owner owns the meter socket and service drop wiring.


Commercial air conditioning systems with variable speed motors are the most likely culprits.  They share the harmonic distortion with all their power grid neighbors.
Is that a consistent 7%, or high during the day and drops at night?  If it's drops at night it is likely Air Con, but even then that is a fair amount of THD. As it is incoming I assume the PS unit is measuring voltage THD.

It's pretty easy to determine if the issue is any part of the circuit from your PS unit all the way back to the transformer. Turn off all the breakers in your house except the one to your PS unit(s), and turn off the equipment connected to the PS. If the distortion is still high, then it's a local line issue not your feed. You could alternately just turn off all the loads in your house but the breakers are probably fastest. Without any loads, any corrosion, etc. will not impact THD.
heaudio123"Turn off all the breakers in your house except the one to your PS unit(s), and turn off the equipment connected to the PS. If the distortion is still high, then it’s a local line issue not your feed. You could alternately just turn off all the loads in your house but the breakers are probably fastest. Without any loads, any corrosion, etc. will not impact THD."

This is completely false, erroneous, and even "Dunning Kruger" in nature regarding it’s ignorance and abject failure to understand even the most basic element of the problem described hear. The PS Audio device itself presents a load to the circuit so any defect in that circuit wiring as has been described as a potential by other contributors to this thread such as bad connections could produce the result described by the OP. Dunning Kruger sails again.
Please ignore my troll. I have triggered him and he posts nonsense after many of my posts.

The static load of your PS audio unit is pretty small when it is not supplying power to anything else. That static load will not impact the THD. 

I am sorry that people like that have to ruin it for others. Feel free to PM me. 
Nurse! Thorazine! Aisle 6. Man down!
You’ve gotten some good answers here, but the distortion problem you’re having could just be the very nature of the electrical distribution system itself. The electrical grid in the US is a very dynamic system. Utilities are routinely seeking to balance loads and efficiently deliver power, and some electric utilities are also under state-mandated reliability improvement programs. So the circuit you are on today may not be the circuit you are on tomorrow. Even your supplying substation may change over time.

That businesses and factories have reduced operations or even closed entirely must have had a huge impact on electric demand and use. At the same time, residential electric use must be on the increase as so many people are confined to their homes, and often working from there, too. All of those factors combined make it likely that your electric utility has made changes to its distribution system. Whether that’s the cause of your distortion is a separate question. It might be a good idea to take the suggestions of @jea48, which might help narrow down the root cause of the distortion and is good advice in any event.
I’m just trying to be helpful here. Noise and distortion are two different things. That why you have the expression for Signal/Noise + Distortion. This all fits in by the way with the discussion regarding the dodgy subject, “What is the signal and why is it subject to vibration, RF interference and physical characteristics of the conductor?“ We’ll get there. Well, maybe we won’t, who the hell knows?
Something else. Do you, or any of your neighbors that share the same utility power transformer, have a solar array electrical power system.

Typically a solar power system would have very low voltage THD unloaded, but the potential for higher current THD loaded. They are measured and rated for current THD.  The output impedance should be a lot lower than the output impedance of a shared transformers unless the system is rather large. To that end, the grid should be dominant but no guarantees. It is certainly something to consider.
So let's say you correctly identify neighbor's A/C or solar panels as the culprit.  What's the point?  
So let's say you correctly identify neighbor's A/C or solar panels as the culprit. What's the point? 
The point is that that you would then know the problem is not with your service entrance or from something inside your home.

Don’t disagree but it seems like instead of guessing about all your neighbor’s potential sources that the best thing would be to do a process of elimination within your own home. Just seems odd all these random guesses about issues outside your home that aren’t actionable.
The best thing would be to determine if it is your own home our outside ... hence the 0 cost, quick method of figuring it out I described above. If you determine its outside your house you may have a remedy with the power company so yes it is actionable.
greetings! I believe any good quality power amp with a regulated power supply should pretty much make AC line distortion a non-issue...
don't you think the average high quality loudspeaker produces 10-15% distortion below 100 hertz/95 decibels anyways...?
@ sm2727

Agon thread.
  Page 2 from the thread. Then read page 3, no more 60Hz hum/buzz


If you don't have one, you can pick up used Fluke 43/43B for < $1,000 used on EBAY which is fine for single-phase use. The Fluke 41B is an older unit, but ones in good condition go for <$500 regularly with required accessories. There is even one with a 1 year warranty for $550. They come standard with 1000:1 current probes with BNC connectors. I have hooked up a 10:1 current probe and used one for low power measurement as well.

The 3 phase units are pricey even used.
@ heaudio123

For about $150 - $200  per hour I can hire a certified Power Quality Testing Company.

That's what the commercial/industrial electrical contractors do in my area. Why spend thousands of dollars for a Power Quality Analyzer, (that will sit on a shelf most of the time) and pay for the training of an electrician for the certification. $150 - $200 per hour is a bargain imo. You even get a certified read out report to hand to the Utility Power Company's EE, if the problem is found to be on their end. It saves a lot finger pointing.

I was not suggesting for the casual user, more for electricians who want to step up their diagnostic capabilities (if they don't have this already), or helpful EEs. If you need a certification training to interpret the basics of what comes out of those meters, then I probably don't want you touching anything I own.

The "certified" Power Quality Testing designation I have heard of is by the Association of Energy Engineers.  Is that what you mean? You don't have to be terribly qualified to enter their program so it feels like another 3 letter designation so popular on LinkedIn profiles and business cards, but conferring questionable abilities on those holding it. Education is great, but as pointed out in another thread 60% and 90% are often both passing grades.
Thank you people.  I will chase it down inside the house.  I looked at the box and nothing looks amiss. I did get a wireless meter but the timing is wrong.... My area has power underground so I don't think it could be storm damage.......at least near here.  If i don't find anything inside i will call the power company.   I will tighten the connections at the box and try the cat and mouse inside the house/check GFI sockets/unplug everything etc. after my kid finishes midterms online.  With my luck I will cabbage my wireless......
  There is constant construction around here (North of Seattle). No new ac on my cul se sac. I assume there is more commercial grade computing going on in my neighborhood.  I have my set up on two different breakers and the reading is identical.....there is nothing between my set up and the box......but i guess (as i read here) it is all shared eventually anyway......I will post when i am done and thank you all....
Please ignore my troll. I have triggered him and he posts nonsense after many of my posts.
 At least he’s (it’s?) trying other styles of prose than adjectives in triplicate. 
I'd suggest that the construction activity may be a source...but only during the 'normal working day'.
If it's at night, or weekends without presence of construction....
It's elsewhere.  
Air compressors, spray gear, older generators, and vehicles aren't designed to be 'quiet' with regard to electronics...but if they're not running...*shrug*
Ok.... so i tried going through the whole house....turned all the breakers off and turned them on one at a time and watched the meter.  No change. I also changed the power source for the power plant to several locations.  It does dip below 6% now so it isn't constant.....Checked the PS audio blog and came away thinking maybe 6 or 7% isn't so crazy.....it is the change that bothers me....
I think it is either just occurring from various sources or it is a power company problem/possibly a change in the power acquisition pattern.    I will call them and explain that i am a tweaky audionut concerned about a changed reading on a "regenerator"  that i use to run my record player  and i can prove it is their fault......i  am sure they will be sympathetic.......
Wish me luck.
Thanks again for the ideas and commiseration.

Believe it or not, power companies may be interested if you get the right person. High THD is not to their benefit or liking.
Ok.... so i tried going through the whole house....turned all the breakers off and turned them on one at a time and watched the meter. No change.

Did you try listening? Its easy to hear. The few times I've done this for people they have all been surprised how big a difference it made. Yet another example of the inadequacy of meters.
I officially recuse myself from this thread as I saw the writing on the wall outlet a long time ago and hopped off the grid about four years ago and never looked back. 👀 No more crappy AC house power, floating grounds, no more power cords, interconnects, no more speaker cables the size of anacondas, no more big honking transformers, no more fuses. They all produce noise and distortion. If you can tolerate noise and distortion more power to you. As Bob Dylan says at the end of all his records, good luck to everybody!
I had the power company come out.  They found nothing unusual.  I have tried listening to my set up and can hear no hum etc.  Frequency is determined by the grid operators counties away..  He said power use is way up because everyone is home clacking away.   I will continue to troubleshoot my house i guess...check sockets for loose wires etc.  I did find a timer that has been running for 15 years without my noticing....whole house fan.   Thanks again for the effort and happy listening everyone.