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

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.
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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......

mkgus OP281 posts

08-31-2021
10:57am


Quick update: I called my utility company and they sent someone out immediately. They discovered that the neutral lug on the homeowner side of the meter was loose and the bolt is stripped. An electrician is on the way to replace the neutral lug.

@ mkgus

Well a loose service neutral in the meter socket could cause problems. Though there is an alternate current path connection from the Line side neutral conductor connection ’IF’ metallic conduit is used for the service wiring from the meter socket to the main disconnect service equipment panel. The neutral bus in the meter socket is bonded, bolted, directly to the back of the metal meter socket. And IF all the conduit fittings and locknuts are tight and solidly electrically connected together the conduit will carry the unbalanced load current from the neutral bar in the main electrical panel to the Line side of the meter socket service neutral conductor. (Neutral bar in the main disconnect electrical panel is bonded, connected, to the panel’s metal enclosure.)


Example of a 1 phase 120/240V 200 amp meter socket. The neutral bus and lugs is located in the center of the socket. Note the bus is bonded, bolted, directly to the back of the enclosure.
https://www.homedepot.com/p/Milbank-200-Amp-4-Terminal-Ringless-Overhead-Underground-Horn-Bypass-Met...

Now if you had said the top neutral lug was stripped causing the Line side service neutral to be loose that could/would cause big problems. You would have noticed while some incandescent lights would dim others would burn brighter. You would have also been replacing the brighter lit light bulbs more often. You also could/would have problems with 120V appliances with motors. Like the refrigerator, washing machine, and such. Even small electronic items failing due to being fed by a high overvoltage.

Here is a video that shows how the secondary of a split phase 240/120V power transformer works.
https://www.youtube.com/watch?v=eVamt9IdQd8

I don’t remember if you said the electrical service is fed overhead or underground.

I could never figure out why the load on the two legs has to be balanced, do your electric devices all turn on and off at the same time? There is always going to be an imbalance.

Yes, 120V loads may be turning on and off at various intervals but there are times the various loads are on at the same time. That is why the known 120V loads should be balanced somewhat within reason on both Lines, legs.
Known 120V loads? Refrigerator, dishwasher, microwave, kitchen two small appliance circuits above the counter tops, chest freezer, central vac, furnace (blower motor. Also used for central air conditioning), cloths washing machine, multiple lighting circuits, sump pump, Bathroom(s) above the counter outlet(s) for hair dryer(s), ect.


Here’s a big problem I see... Occasionally I will read a post on an audio forum where the home owner, audiophile, on his own moved all the 120V motor loads, plus micro wave, and other such loads to one Line, leg, and have his audio equipment on the other Line, leg. This is not good for the home owner’s electrical service or the utility power company’s transformer. Especially the utility power transformer. The power company does not size the transformer by adding up the size, amperage rating, of all the electrical services that are fed from the transformer. The Power Company roughly calculates the average demand load that might be placed on the transformer. A power transformer is most efficient when it is loaded near its rated KVA rating. A Utility Company never adds in a fudge factor when sizing the transformer. Fudge costs money...

The secondary of a typical residential housing development power transformer have what is called a split phase winding. It will have a 240 volt winding that is tapped at its center point. From either outer lead, leg, of the 240 volt winding to the center tap (neutral) it will measure 120 volt, nominal. Basically two 120V windings that are in series are created. With this type of a winding only the unbalanced 120V loads return on the service neutral conductor to the transformer neutral. The balanced Line 1 (L1) to neutral and Line 2 (L2) to neutral 120V loads are in series with one another and are being fed by 240V.

Example, if there is a total combined load connected to L1 to neutral of 50 amps and a total combined load of 40 amps connected to L2 to neutral, only 10 amps will return on the service neutral conductor to the transformer neutral. The balanced 40 amps on each Line, leg, will be in series and will be fed by 240V. The transformer will see a total of 40 amps through the entire 240V winding and an additional 10 amps through L1 to neutral split winding.

Here is an example of a step down split phase secondary winding transformer. Such a transformer might be used to feed an audio system’s equipment. Primary wired 240V secondary 3 wire 120/240V. I will use a 10KVA power transformer with dual voltage 120V/240V secondary windings for the example. The secondary has two windings. Each winding is rated for half of the 10KVA, therein 5KVA each. Each winding has a voltage rating of 120V, nominal.

Some math:

5KVA / 120V = 41.67 amps maximum FLA.

So if the transformer’s secondary is configured, wired, as a 3 wire 120/240V power system from each Line, (L), leg, to the neutral leg the maximum 120V load(s) that could be connected is 41.67 amps.

L1 to neutral 120V load(s) 41.67 amps and L2 to neutral 120V load(s) 41.67 amps.

The two secondary windings are wired in series. The center point of the two windings is the neutral. (Per electrical code the neutral shall be grounded). From either outer lead, leg, to the neutral will measure 120V. From the outer leads, legs, of the entire series winding the voltage measures 240V. (5KVA + 5KVA = 10KVA / 240V = 41.67 amps maximum.)

For a full connected load example:

If L1 to neutral has a connected load of exactly 41.67 amps and L2 to neutral has a connected load of exactly 41.67 amps, zero amps will return on the neutral conductor to the center point (neutral) connection of the two series connected windings. The two 41.67A loads are in series with one another and fed from 240V. Current through the series 240V winding will be 41.67 amps. 240V X 41.67A = 10KVA... 10KVA / 240V = 41.67A

(Note: The neutral connection for each 120V load is still, must be, connected to the transformer neutral leg. The connection maintains a stable 120, nominal, voltage).

/ / / / / / / /

If the above secondary winding configuration is used to feed an electrical panel that will feed audio equipment the two 120V Lines, legs, 120V loads should be balanced somewhat within reason to draw power from both windings of the secondary. Say you have two mono amps that have an FLA of 8 amps each you would not want to put both amps on the same Line to neutral. That would load up one winding of the secondary. The correct way would be to connect one amp to L1 to neutral and the other amp to L2 to neutral. The balanced 120V loads of the two mono amps will be in series and fed by 240V.

How about those that say that all audio equipment that is connected together by wire interconnects should be fed from the same Line, leg, to neutral? Well as you can see from above if all the equipment was fed from just one Line, leg to neutral only one secondary winding of the 10KVA transformer would be used. 5KVA with a maximum FLA connected load rating of 41.67 amps.

If you want to have all your audio equipment fed from one Line, leg, and still have the full 10KVA rating power available wire both secondary windings in parallel, (OBSERVING POLARITY). In parallel the voltage out will be 120V only.

The full 10KVA power rating is available.(5KVA + 5KVA). Maximum amperage rating available for 120V is 83.33 amps.

10KVA / 120V = 83.33 amps.

Primary of transformer wired 240V, secondary wired for 120V.

(One leg of the 120V secondary shall be grounded)...

(An electrical panel is required).

/ / / / / / / /

How a 3 wire single phase split phase transformer winding works:

https://www.youtube.com/watch?v=eVamt9IdQd8

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The reason that many (including me) say that equipment ought to be on one leg, is that in fact I say it must be plugged into the exact same outlet (with outlet strips as needed. This is the only way to minimize ground loops.

I am also a believer in feeding audio equipment, (that is connected together by wire interconnects), from the same Line, leg. I do not subscribe to the theory the equipment must be plugged into the same outlet to prevent the chance of ground loops though.

I have two 20 amp dedicated branch circuits that are 75ft each. Wiring is 10/2 NM cable, (Romex Trade Name). Both circuits are fed from 20 amp breakers that are directly across from one another... My system is dead quiet.
(Tube power amp and tube preamp).

Dedicated circuits get a bad rap and are wrongly blamed for ground loop hum, imo...
Things to blame:
1) Poorly designed audio equipment that uses an EGC where the circuit designer directly connected the power supply B- / signal ground to the chassis/EGC.
2) The wrong type of branch circuit wiring was used.
3) The wrong wiring method, installation, was used.


See page16 and read pages 31 thru 36.
An Overview of Audio System Grounding and Interfacing

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