How To Do You Measure the Quality of Your AC Power?

None of these people will find anything wrong, because from their point of view there is nothing wrong.

Perspective is everything.  Last year I was checking the electrical in a place in Ixtapa.  Found all kinds of problems from reversed polarity on wall plugs, missing ground wires..........    I asked a local "electrician" if there were any standards they followed when wiring a home.  He asked me "is the fridge cold?  Do the lights come on?  Then what is the problem?"   

Sounds like a classic bad mains issue. I had a similar issue with dimming upon load. Turned out to be a bad connector on one of the 120v mains on the power pole. As many above have suggested, call the Power Co. If mains are good, find a better electrician. Beyond that, the rabbit hole is deep.... An isolated ground circuit is helpful, but still shares grounding at the box. I like an a large ungrounded (yeah probably not to code) isolation transformer (larger than the sum of VA or watts of the equipment) to start..... 

@Mkgus  You could look at our purchasing a line conditioner.There is one made by Trip lite I think it's around 90 .00 it will not only protect against spikes but it regulate the voltage. If the voltage dropped to say 85 volts on your circuit feeding your audio system it we correct it to 120, also if it went to high say 130 it will also correct back to 120. Also a whole house surge suppression ( breaker) depending on the panels manufacturer would also help protect the circuits feeding your audio system as well as rest of the house. If you have power and all seems to work fluctuations are tough to troubleshoot and actually repair some people don't know there occuring. The conditioner will help with some piece of mind yes I have a clean 120v for the circuit.

take the advice of MC. He is the only one here that has actually done it".....  

To wit:

What you do is what everyone does. Make all your connections from the panel to your room as clean and tight AND FEW as possible. This is where the "dedicated" (which really means direct) line comes in. Then from there you use as good quality outlet, power cords, and conditioner as you can.  
The better the quality, the better the results.

Strip away all the blather above and this is what you get. Every time.

They make tools for evaluating and testing your power to your house but i would try to just run a dedicated line to your stereo and that should help significantly for you sound and be sure to connect all of your equipment to the dedicated line so it is all at the same ground potential.

EMI:  Time domain (i.e. oscilloscope) measurements are more relevant than frequency-domain ones (i.e. spectrum) simply because spectrum analyzers (with the exception of really expensive ones) would miss transients which dominate the type of electrical noise present on power lines and ground.   Measure both common mode (i.e. between Live/Neutral and ground) and differential (between Live and Neutral).  Here is an article I wrote on the subject for inCompliance Magazine that deals with these things: https://incompliancemag.com/article/measurements-of-conducted-emi-in-the-manufacturing-environment/   The tools to use: a portable digital scope (I use Hantek 1200 family, but others can be just as good - just make sure that the bandwidth is at least 100MHz), and power line EMI Adapter MSN17 (https://www.onfilter.com/emi-adapter-msn17) otherwise you won't be able to make any relevant measurements and can kill your oscilloscope.  Stay away from the tools that give you fuzzy relative data and no specification.
If you are interested in harmonics, you can use the same oscilloscope (make sure it has FFT - most do.   Read the user's guide!) and 100:1 probe.  Scope must be in battery-powered mode only!  Unless harmonics are quite severe (at the factories I have seen quite a bit, but not at homes), they are unlikely to affect anything of importance in this case.

Make sure your switches and outlets use real wire wrapped screw tightened connectors.

The little hole for the backstab connections are poor and I'm not even sure they are legal anymore. 

I don’t think the electrician did any of that. I should have hired you! I think it was more of, “Well I tightened what lugs I could and no breakers are flipping so you don’t have a problem.” Thanks for all the good advice.

What a freaking waste of time and money. None of these people will find anything wrong, because from their point of view there is nothing wrong.

Multiple electricians have failed to find anything wrong with my electrical system or electrical panel.

Exactly. There is nothing wrong. Sorry, but there just isn’t.

Qualifications of the electricians? Years of experience in troubleshooting?
Were the electricians just residential electricians, or journeyman electricians with years of hands on practical experience troubleshooting electrical problems in commercial and industrial facilities? Yeah, it makes a difference.

Here is what an average electrician should do, and check for, in an electrical panel.

1) check voltage. Line to Line and each Line to neutral. He/she should also check Line to EG bar voltage to verify the Main Bonding Jumper is effectively bonding the service entrance neutral conductor to the metal enclosure of the panel.

2) Hopefully the electrician has a Thermal Imaging Camera to check for corroded and or poor electrical connection hot spots. Or maybe he/she just has a cheap temperature sensing handheld device for checking for hot spots. (All loads should be turned on if possible. Especially high amperage usage loads).
Corroded and or loose connections can cause series light arcing which in turn can cause harmonic distortion on the mains. Even bad seating contacts in a breaker(s) can cause harmonic distortion on the mains. That also goes for the Main breaker. Same goes for the Line side connection of the breaker to bus tie connection.
Did any of the electricians have the equipment to test for temperature hot spots MC?

3) If no hot spots are detected the electrician still should look for any signs of corrosion at all wire to breaker terminations. Especially on the service conductors feeding the main breaker or main lugs, if the main breaker is elsewhere. You would be surprised how many service entrance conductor terminations at the electrical panel show signs of corrosion.

4) The electrician should check the Grounding Electrode System for corrosion and tightness of all connections. (Grounding electrode system is the wiring and clamps used to connect the service entrance neutral conductor and service equipment enclosure to mother earth.

5) If the panel is fairly old and has aluminum bus the breaker to bus tie connection should be checked for possible burn arcing hot spots. Especially known loaded branch circuit breakers.
Go through all the electrical connections in the panel for wire to terminal tightness. Conductors to breaker terminations. Neutral conductors to neutral bar terminations. And EGC to EG Bar terminations. Check tightness on service entrance conductors at main breaker or main lugs. Check service entrance neutral conductor lug for tightness.

FWIW I have read at least 4 threads on various audio forums over the years where the OP asked basically the same questions as the OP on this thread. In the end the problem was found in the meter socket of an overhead fed electrical service.
Rain water over the years can find its way through the weather head and inside the mast conduit and travel down the conductors and collect on the Line side of the termination lugs. Over the years the water causes corrosion and causes the connection to deteriorate. That in turn causes a small amount of series arcing in the connection(s). That in turn causes harmonic distortion on the mains. The greater the connected load on the corroded connection(s) the greater the percentage of harmonic distortion on the mains.

It won’t cost the OP a PENNY to call the Utility Power Company. Just a little bit of his time.
Or just take the advice of MC. He will tell you "He is the only one here that has actually done it".....  

Best regards......

Besides poor audio quality, two examples of what I’m experiencing are:

1) Playing music with bass at low to moderate levels causes dimming lights.
2) Slowly walking on a treadmill causes the lights in the room to substantially dim with each foot step.

I’ve had electricians tell me that the best way to wire things is to have the lights and outlets on separate circuits so that things like treadmills don’t dim the lights, but there’s just no way a slow paced walk on the treadmill is pulling down the voltage that much on a normally functioning electric service. The problem seems to affect the whole house which makes me think it’s upstream of my panel. I’ve had all the lugs in my panel tightened and I even dug up the top of the ground rod to verify it’s connected and it is.

That’s exactly the type of thing I wanted to hear about, tvad. Thank you!

Early in 2020, on the recommendation of my electrician and @jea48, I contacted our Power Company and requested a power quality analysis. They installed a special meter and downloaded weekly readings for a month. It resulted in some repairs to our service, and to neighbors’ service. One repair improved voltage consistency. 

It was free. Well worth investigating.

Maybe, but maybe not. What I have noticed about electricians and electrical engineers is that they approach it from the perspective of meeting code and not starting fires. That’s not a bad thing in general, but if you’re chasing high fidelity sound you’re going to have a bad time with that approach (minus the not starting fires goal, haha!)

If code allows for a 5% voltage drop in a 120V line, then you’ll see fluctuations between 114 volts and 120 volts depending on the load. That’s completely unacceptable for hi-fidelity sound. You want that voltage sitting at 120 constant and not budging an inch. Sure, a good power supply will minimize the effects of voltage fluctuations but why would you want to deal with that hurdle if you don’t have to? Make it as easy as possible for your equipment to perform, which means going well beyond what a code book would tell you. 

Your advice with a dedicated line is spot on, however, it won’t fix problems upstream of your panel such as a loose lug on the meter socket. There are other things going on outside of my audio system that strongly indicates a poor ground or bad neutral connection.

I could pull a dedicated line, I could buy a filter, I could buy a regenerator, and I probably will some day, but there has to be a better method than “just try whatever and see what helps.” If you can diagnose the problem properly, then you can apply focused solutions which saves time, money and headaches.

What a freaking waste of time and money. None of these people will find anything wrong, because from their point of view there is nothing wrong.

Multiple electricians have failed to find anything wrong with my electrical system or electrical panel. 

Exactly. There is nothing wrong. Sorry, but there just isn't.  

Only thing wrong is your approach. You heard a difference and assume this means there is some glaring fault somewhere to be fixed. There isn't. Instead there is just the normal problem of noise coming into the line.   

The kind of noise we are talking about is endemic, and involves everything from RFI from radio, cell phones, and appliances, to EMF from everything connected to power everywhere.  

It is what it is. What you do is what everyone does. Make all your connections from the panel to your room as clean and tight AND FEW as possible. This is where the "dedicated" (which really means direct) line comes in. Then from there you use as good quality outlet, power cords, and conditioner as you can.   

The better the quality, the better the results. Results which are by the way determined by ear, not by meter. Unless your system goal is to sit in the dark looking at a meter?

Hire a Power Quality Testing Company. Cost per hour $150 - $250. A heck of a lot cheaper than buying a Power Quality Analyzer.
Example of a Power Quality Analzer:
You would only need one for single phase power.
https://www.myflukestore.com/category/fluke_power_quality_analyzers

At this point, I believe the power quality from the city may be poor but I’m not sure how best to measure it. I also have a hunch that there is a loose connection somewhere between the utility transformer and my breaker panel.

Before I bug the city, I would like to be able to provide measurements that something is wrong,

Bug the Utility Power Company first.
Call them and ask who you can talk to about your power problem. Usually it will be an EE. Nicely ask him/her if a tech could come to your home and check for a problem(s) from the load side of their meter to their utility power transformer. Again, nicely ask for their help.

The tech will pull the meter and visually inspect the meter socket electrical connections for corrosion and for any evidence of a loose connection. He may even check the mechanical lugs for tightness. Loose and or corroded terminations can cause harmonic distortion on the mains. If everything looks good in the meter socket hopefully he will plug in a device that will allow the tech to test for power quality. He will plug the meter back in to the device and will return after a couple of days to review the collected data. The tech should supply you with a hard copy test report.

Sometimes the tech will connect the power quality analyzer at the main electrical service panel ahead of the main breaker. It just depends on the Power Company’s testing policy.


FWIW. A single phase 240/120V electrical service fed by an overhead power line will have a minimum of 18 to 22 electrical connections from the transformer to the Line side of the service equipment main breaker and service entrance neutral conductor connection in the service equipment enclosure/ panel.
Most of the electrical connections exposed to the elements, harsh conditions, of mother nature.
Wind, heat, cold, rain, high humidity, snow, and ice.
.

A little backstory for the curious: When I moved to my current house, my audio quality decreased substantially. I spent a great deal of time investigating this and believe I’ve narrowed it down to the AC main. Multiple electricians have failed to find anything wrong with my electrical system or electrical panel. At this point, I believe the power quality from the city may be poor but I’m not sure how best to measure it. I also have a hunch that there is a loose connection somewhere between the utility transformer and my breaker panel. Before I bug the city, I would like to be able to provide measurements that something is wrong, but I don’t know how best to do that. Also, from a recent utility locate, it looks like the underground power goes from the transformer to my neighbors house and then to my house. Is that standard wiring procedure?