How does the typical mains power connect in the USA anyway?

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Danny D'Amico formulated on Wednesday :

In Delta configuration there is NO Neutral so whats you point.
The POwer generator almost always uses DELTA configuration of the HV and Vvery HV lines with only 3 three wires.
The last leg from the local substation to the street transformers (POLE PIG) will likely be WYE so that each PP only gets a phase and neutral to convert to 240 volts centre tapped.
--
John G



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On Tue, 26 Nov 2013 07:11:01 -0800, snipped-for-privacy@optonline.net wrote:

At least I posted a reference.
Now, if that reference is "fatally flawed", then the dozen sites that repeated it *should* have vetted the information more fully.
Still, at least I posted a reference that directly discussed the issue, which is more than those with the opposing view provided.
Note: The 10-page PDF on ground distribution was complex, and, after reading all ten pages, never *directly* discussed the issue, although I'm sure I'll be reamed for stating that since the *entire* paper was all about grounding paths (but very technical).
As a (retired) accountant, we never covered *this* stuff in college way back when.
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On Wed, 27 Nov 2013 06:30:39 +0000 (UTC), Danny D'Amico

You mean like you did before you referenced it?

Time is short.

The engineers, here, did.
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nestork wrote:

Hmmm, You are trying to say if I and V is out of phase by certain degree there will be a current flow which is wasteful. That current does not do any work. That is why in big industrial site or buildings use power factor correction device.
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Tony Hwang;3155652 Wrote: >

No, houses very rarely have power factor correction. Most of the reason why is that electrical utilities only charge their residential customers on the actual kilowatts they used, not the KVA the consumed. So, why have power factor correction if it's not going to save you any money on your electric bill?
I'm saying that in the real life situation, electrical loads being carried by L1 and L2 are rarely ever going to be perfectly balanced. The result is always going to be some timing differences in the current sine waves travelling in the white wires returning to the electrical panel. The result is going to be a "net current sine wave" as a result of superposition of all the individual current sine waves in the neutral buss in the main panel.
You can't have current without voltage. Ergo, there is always going to be some net voltage sine wave in that neutral buss, and therefore in the ground wire cable coming out of the main panel. So, how can you NOT have current into and out of the Good Earth through the grounding rod or pipe if there is a voltage imposed on that grounding cable by the white buss?
I'm not saying that current flows back to the generating station through the ground. Or, at least, I'm not saying that yet.
I'm saying that electrical loads are rarely going to be perfectly balanced, and any imbalance in the impedance of electrical loads is going to cause timing differences in the amperage sine waves carried by the white wires connected to the neutral buss in the main panel. That means there HAS TO BE some net voltage sine wave in that neutral buss to drive that net current sine wave.
And, I can't see why a net voltage sine wave in the neutral buss wouldn't cause current flow into and out of the Good Earth at the grounding rod or plumbing pipe.
And, according to one of the pictures posted by G. Fretwell, the current measured through his grounding rod is 0.142 amps. And that's without any intentional effort to imbalance the electrical load at the main panel.
Where am I wrong there?
--
nestork


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On Tue, 26 Nov 2013 08:20:23 +0100, nestork wrote:

I always thought they only measured current at the meter?

Agreed.

:)

Exactly!

When it gets light, and I take care of the grandkids getting to school, I'm going to see if I can find my old ammeter and I'm going to check my neutral and ground wires too!
Those pictures from gfrewell were inspiring! We can make our own observations!
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On Tuesday, November 26, 2013 8:22:48 AM UTC-5, Danny D'Amico wrote:

Which again shows how little you know.

Wrong.
Example: I have just a couple of 240V loads. Zero flow in neutral.

Exactly what? That current flow is tiny and incidental. It's is *not* delivering 99.99% of the power. You could unhook the ground and power would still be delivered.

Last time after you did some experimenting your alarm system was toast. What's next?

What in the world does him showing a tiny .14 amps flowing in a ground have to do with your claim that the earth is used as the return path for power transmission?
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It would appear that the concept of electrical continuity and being part of a circuit is rather lost on some people. Does the ground perform an important function? Yes. Is it a current carrying entity in the circuit: No. Does it carry stray voltage? Yes. Does it carry stray current? Yes. Does the fact that it does carry voltage and current make it part of the distribution system? No.
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On 11/26/2013 1:20 AM, nestork wrote:

The current in the legs of a split phase service are not likely to ever be balanced with a zero neutral current, so most of your post is kinda irrelevant. There will be a neutral current.
Since the utility transformer neutral is earthed, and the house service neutral is earthed, the earth is a parallel path to the neutral wire. That produces some current in the parallel earth path. But the resistance of the neutral wire is far lower than the ground path. A very good resistance to earth at a house might be 10 ohms. What is the resistance of the neutral wire? What fraction of the neutral current takes the parallel earth path? Not much.
This earth current is not an intentional current flow, but a result of how electrical systems are earthed for safety. Electrical systems use a metal path for power distribution.
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bud-- scrit:

The return path is intentional in so much as the system is engineered to take it all into account because it's going to happen. All over the place.
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On 11/26/2013 12:07 PM, Harold W. wrote:

I don't know what "engineered to take it all into account" means.
Engineers would rather not have these earth currents. One place they are quite detrimental is on a dairy farm where "stray currents" can have a really large effect on milk production.
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On Tuesday, November 26, 2013 2:20:23 AM UTC-5, nestork wrote:

Usually there is going to be some current flow, specifically the unbalanced portion. But if the only loads on are 240V, eg oven and water heater, then you would have zero current flow in the neutral. Or if you had that and you put two 100W 120V light bulbs, one on each leg/phase, then again you'd have zero current flow in the neutral.
So, how can you NOT

Yes, if there is current flow in the neutral, then some smaller portion of that current will flow through the earth, back to the transformer. It will divide according to the impedance of the neutral vs the impedance of the earth. The neutral is going to have a lot less impedance, hence most of the current is going that way. Also, that current is incidental, it's *not* the primary path and it's not being relied on to deliver power. THAT last part is what Danny doesn't get.

Thank God.

Generally correct, except for the timing difference part. Assuming pure resistance loads, there are no timing difference in the various loads. And adding power factor, which would get you timing differences, would only obfuscate the issue.

If the loads aren't balanced, then yes a small portion of that unbalanced current is going to flow back to the transformer via earth. The vast majority of it is going to flow back via the lower impedance neutral.

You've basically got it correct. The big disagreement with Danny is that he's insisting that the power company uses the earth as a return conductor to deliver power. That's what is wrong. In the .142 amps example, it's an insignificant part of the power.
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On Tue, 26 Nov 2013 10:40:04 -0800, snipped-for-privacy@optonline.net wrote:

Which is why I had asked the question ... :)
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On Wednesday, November 27, 2013 1:32:04 AM UTC-5, Danny D'Amico wrote:

It's not that you asked the question, it's that you wouldn't accept the answer even after it's been explained to you by several EE's, electricians, etc. And we did give you references along the way, you just didn't even acknowledge most of them. Including the one I gave you from Wikepedia that shows how power is transmitted from a 3 phase power source to a 3 phase load, the current flows, and it can be done over just the 3 phase wires. There is no earth path there and if you looked at the animation, you can see that it's not needed.
Here's another puzzling angle. You appeared to understand the difference between a neutral and ground in your own panel after it was explained to you. Well, if using the earth as a return path for power is how power is routinely deliverd, what is that neutral doing there? Why waste money on it? The center tap of the transformer is grounded, your house neutral bar is grounded. They are only a couple hundred feet away. So, why do they have that neutral wire there if the earth is just as good?
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On Tue, 26 Nov 2013 05:55:20 +0100, nestork

Nothing. A small amount of the unbalanced neutral current does go back through the ground. You can see it on the ground wire going up the pole to the XO on the pole pig.
http://gfretwell.com/electrical/Pole%20at%20my%20house.jpg
This is the voltage drop across the service cable from the pole to the house.
http://gfretwell.com/electrical/VD%20on%20drop.jpg
There is also quite a bit of voltage drop on the primary and that shows up through the ground wire. This is the first pole on the street.
http://gfretwell.com/electrical/First%20xfmr.jpg
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On Tue, 26 Nov 2013 00:58:15 -0500, gfretwell wrote:

That is a gorgeously illustrative picture!
I see 860mA of current going through that wire into the ground on your side of the transformer.
I presume 860mA would be considered indicative of a reasonably well balanced set of loads inside your home?

Another beautiful picture! Is that 142mV RMS? If so, there's essentially no voltage drop from the transformer to the home. Right?

That picture seems to show 2.95A flowing through the ground wire!
If that is on the primary side, wouldn't *that* be the current which is (essentially) flowing back to the power company?
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On Tue, 26 Nov 2013 06:15:13 +0000 (UTC), Danny D'Amico

Since this is wye distribution, it would be reconciled at the transformer that steps down the HV to MV where it goes to delta distribution but some of that would just go to the next series of poles on the other primary phases.
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On Tue, 26 Nov 2013 05:55:20 +0100, nestork

Correct.

Sure, that's why you have a neutral, to carry the difference in the current of the two legs. That's why it has to be the same gauge as the hots, unless it's a certain size (where cancellation can be assured).

Sure. So? That's what the neutral is for. Add to this, the harmonic content from your switching power supplies and fluroescent lights. It gets ugly.

Sure. There *is* current in the neutral. That's the reason it's there.

What's the resistance of the wire?

The resistance of the wire.
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After bud's excellent explanation, we can see that Danny is almost right.
The ground IS a parallel path for return, but most of the current will flow along the neutral wire.
If there's not a neutral wire, then..........no don't go there. Yet.
Back to that single phase feeding the house from the transformer secondary for a second.
The center tap of that transformer is bonded to ground. That gives us a ze ro reference. But that technically is not necessary. Your house would wor k fine without it. Your oven would still "see" 240 volts and your lights 1 20. The problem is you might have a voltage difference between some of you r equipment and ground.
But transformers are not limited to one tap. This secondary could easily b e tapped at 60, 120, 180 and 240 volts referenced from tap to "low" termina l.
Do I now have 4-phase power? Do I have four legs out of phase?
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wrote:

At a certain point we have to stop all of the "phase" BS and just say this is single phase. Anything else is just wrong. Split phase refers to the way some motors are wound and two phase is something else altogether (4 wires with 2 phases 90 degrees out) Standard 120/240v service is single phase that just happens to be grounded on the center tap.
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