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

They tested the line from the street to my meter. I don’t know what they tested exactly. Is that the same thing?

They tested the line from the street to my meter. I don’t know what they tested exactly. Is that the same thing?

At our place, the power quality survey took four weeks. They installed a special meter at our service panel from which they downloaded data once a week for four weeks. The initial visit entailed checking the voltage on the lines, checking the connections at the service panel and power pole, and testing continuity of all the breakers.

So, not the same thing.

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.

It’s fed underground. 
Another update:

The electrician came out and repaired the bad neutral lug and tightened everything up. The utility turned the power back on. The first thing I did was run some “tests.” Dimmable lights that used to buzz loud are quieter, the treadmill no longer dims the lights with each footfall (it does a little bit but it seems normal now whereas before it was like being at a rave), and best of all the sound quality of my audio system improved! No wonder - I’m sure the current flowing through the bad neutral lug wasn’t helping in any way with power delivery!

I’m really glad I put in the effort to follow through on this. I am very thankful for all the good advice from this community! I knew something was wrong with the power. I am happy that I didn’t go off on tangents with dedicated lines or power regenerators. I still plan on doing those things, but they would not have completely solved my problem in this case.

I had 3 dedicated lines installed a year ago and now wish I had 5.  Each line had a new breaker, I wish I had replaced all the breakers.

I have a PS Audio P10 Powerplant.  I never get 0 % distortion but the readout says it is better.  I have noticed the P10 adds its own distortion to the line depending on various settings.  It can be a very detrimental effect.  I only use the P10 for my digital gear and it is on its own dedicated line.

The P10 is very susceptible to line noise from the components on it.  I had to remove 2 SMPS's as they were injection an awful distortion.  

On the subject of SMPS's I found a great benefit taking them off all of my dedicated lines.

Interesting. I am in the same situation as you. I have a couple SMPS’s on the same circuit as my other gear. I could power them off a 12V battery using a 120V AC inverter or run a dedicated line for them. I wonder if my amplifier would sound better without those SMPS’s on the same circuit. I also wonder if they interfere with each other.

 I wonder if my amplifier would sound better without those SMPS’s on the same circuit. I also wonder if they interfere with each other.

Not if your amplifier is competently designed.

Save your money. Power regenerators do absolutely nothing for sound quality unless your components are very poorly designed. You’ll be better off upgrading your system components. When you own good gear you’ll find that distortion on your grid has absolutely no bearing on sound quality. Companies like PS Audio thrive off hawking such garbage because they’ve realized most audiophiles don’t have any clue how their gear works. 

use a power plug extreme 
made in china for only 10$

Power regenerators do absolutely nothing for sound quality unless your components are very poorly designed.

In my experience, everything is on a spectrum. It’s not binary. Clean power is very, very important. Every time I’ve cleaned up my power in any way, I’ve experienced positive results. The better designed equipment didn’t benefit quite as much as inferior designs. In the end, it’s up to the listener. Does a specific power upgrade provide enough benefit to justify the cost?

I use something very similar to this little gadget since it measures the main and neutral at the same time.

A good indicator of poor or loose wiring is either the main voltage dropping, or the neutral voltage rising.


https://amzn.to/3m0kEzW

Sadly the one I actually use is no longer carried, but you get the idea.

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.

The requirement to be balanced is not to within 0.0001 %, but to avoid severe imbalances, especially at 50% or higher load. Being within 20% is probably OK. This reduces the need for the neutral to be 2x as big, and I believe also has consequences on the transformer.

If you have a 200A service and are drawing 30A you care a lot less.

Let's disambiguate. (is that  word?)
Typically we worry about Noise. MC went on (correcly) on noise. The only solutions involve various type sof filtering, including normal filters and (better) isolation transformers. Bear in mind that YOU are likely the biggest polluter with your PC, TV, etc right there in your house.  Make sure you have filters between those noises and your sensitive analog components.

Now on to some things you said about lights dimming etc. under loads. This is a very different issue, that comes from a hgih impedance of the AC line - maybe from the utility, but also maybe your own wiring.  I have two "home run" outlets from my listening room to the 200A service in my garage that is on 12 AWG copper and bypasses all the other house wiring.  I also have several filters (all home made). But they do jack $H1T for hgih impedance (aka: low current capability - same deal).  An electrician ought to be able to find this - basically you load test it just like you load test your batter y and alternator in your car. Apply load; measure voltage drop.


BTW noise on the line changes every minute, second, hour, day and season. One measurement means little.

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

.

@jea48 :
Careful. You're talking mostly about things that impact the power company and/or maximum utilization of your step down trans.  Nice, but not huge sonic issues.  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.

Since  your equipment in aggregate is probably drawing 100-400 watts maximum, its really no big deal.

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

.

I've never encountered a ground loop from running more than one dedicated outlet, it would be rare. I think some mistake noise in the system to a ground loop.

I'm simply saying that i have used this in many systems to remove a ground loop hum.  Sometimes you have the same reference on two outlets, sometimes you don't.  But the simple fact that they are not the same places violates the principle of star grounding out of the gate.

I think some mistake noise in the system to a ground loop.

Let me preface with "not trying to be argumentative" - you both seem to know what you're doing and have things under control. But let's nto tell others that up is down or up isn't really high enough to matter.

I’ll answer to both of you guys (immediately above) that a star ground is the gold standard. And while you may claim things are "good enough" or "not a big deal" any divergence is in fact wrong -- less than ideal. period.

Any resistance between reference points can result in noise of various kinds - in AC power typically 60Hz or 50 Hz (outside ’murica). Why bait fate? You are simply arguing that you can sometimes get away with it. we can get away with many things, until we’re caught.


Now, when you move all the plugs/grounds to one circuit,and the hum decreases, you know its source. Its a reference differential. So there ought to be no mistake if you follow the golden rule: don’t change anything else, one variable per equation please.