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

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John G;3153423 Wrote: >

John:
In here, we all learn from each other.
None of us knows everything, but all of us know some things. We collectively share what we know so that we're all better off for it. That's how we get along.
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nestork


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nestork pretended :

Thats OK and I respect it But we do not need people who do not know what they are talking about spreading rubbish.
Ask questions by all means but leave out talking about things unknown as though you are the expert.
In this particular thread there has been so much ignorance portrayed as fact I thought it needed some correction. :-?
--
John G



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John G;3153533 Wrote: >

>

Constructive criticism is always welcome in here.
--
nestork


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On Sat, 23 Nov 2013 14:40:59 +1100, John G wrote:

Hi Nestork & John,
The problem is my fault. I was making a joke, but, even with the smiley, nobody got the joke.
I always tell my grandkids that if nobody gets the joke, then it's the fault of the jokester.
So, while the 6 wires did look pretty, we all know they were all hot wires. I didn't think anyone would think otherwise, so, that's why I snapped the picture and posted it.
It was just to point out that you *can* have six wires; but, they're all hot in this case!
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On Sun, 24 Nov 2013 00:54:46 +0000, Danny D'Amico wrote:

I just found where I actually said the joke, and, well, it's pretty clear to me that I was joking. Oh well. It's still my fault if nobody got it.
Here is the exact quote that was snipped out prior. Notice I first explained that the ground is the return path for the three 120-degrees-out-of-phase hot wires, and then I added the one sentence (with a smiley) that got me in trouble:
Apologies in advance for the top posting - but here is the post in toto:
On Fri, 22 Nov 2013 09:47:51 +0000, Danny D'Amico wrote:

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On Sat, 23 Nov 2013 10:02:08 +1100, John G wrote:

I *knew* they were all hot wires! You have to notice the smiley sign at the end the sentence.
I've previously said that there is three phase (120 degrees out of phase) transmission and distribution, so, it's clear that I knew they were hots.
I happened to go to lunch with friends in San Jose and I saw the 6 wires, and I thought of this discussion, so I snapped a picture of the 6 wires, to show the team.
I do agree with you wholeheartedly. The GROUND is the conductor back to the power plant (theoretically anyway). Clearly the wires I snapped are three phase wires, and clearly the six wires are all are hot.
The insulators were gorgeous but the distant picture cropped doesn't show how beautifully they shone with iridescent greenishblue colors.
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It is called parallel conductors. Two smaller cables take the place of one large cable. Cost less, and carries a higher current since the cross section of the smaller conductors cools more readily in open air than one large conductor would. Both ends terminate, respectively, at a single point. There are rules for this, too, but that is another topic.
Most generators have at least one set of parallel conductors inside, and have, usually, three sets(or more) going to the distribution bus of the power plant. Depends on voltage, of course, and not all generators are the same, so there are differences.
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On Mon, 18 Nov 2013 07:08:23 -0800, TimR wrote:

I was always of the opinion that the ground was the second set of three wires. That is, the power company grabs electrons from the ground, and then it sends those electrons over three wires, 120 degrees out of phase, and then the electrons return to the power company through the ground.
It's a huge loop. At least the way I understand it.
BTW, here are six wires, but they're not the same thing! :)
http://farm8.staticflickr.com/7456/10991456846_b2349dd5b6_o.gif
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On Mon, 18 Nov 2013 18:09:29 +0100, nestork wrote:

That was interesting. Notice the 7200V primary side of the transformer didn't look grounded in the picture (but it must have been). Right?
Also, the ground (literally) was stated as being part of the circuit (although I would have like them to complete the circuit at your lamp, and then *back* to the power company (via the ground).
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Danny D'Amico was thinking very hard :

If you had any understanding of electricity you could understand that the GROUND is not part of the circuit. It is there to keep all the parts of the system at the same reference potential.
A 3 phase Delta system requires only 3 wires. A 3 phase Wye system has 4 wires to allow connection to the center point and one phase to get a lower voltage than that between any 2 phases but a symetrical 3 phase load of the correct voltage only needs 3 wires.
The ground is only for safety and is, by code, connected to the neutral at each customer.
The USA system delivers only ONE 240 volt supply to houses and the neutral is really only a centre tap of that to get 120 volts for small appliances.
I know there are variations (too complicated to explain here) but the overall principle remains.
The ground wire plays no part in a proper fault free system. No current flows in around or thru the ground if all the conductors are installed to code. :-Z
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John G



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On Friday, November 22, 2013 6:17:08 PM UTC-5, John G wrote:

I agree with 99% of the above, except the last sentence. You will have some very small portion of the current flowing through the ground. Take for example the simple case of the neutral and ground of a 240/120V service being tied together at the house and at the transformer. Those are two paths for current to flow, just like two resistors in parallel. The vast majority of the current will flow in the neutral conductor because of it's low resistance. Some small amount, however will flow in the ground path, with it's higher resistance.
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On Sat, 23 Nov 2013 10:17:08 +1100, John G wrote:

Well, I *thought* I understood electricity, in that without a "loop", there would be no current.
What I *think* is the real answer, albeit it's hard grasp because the earth itself is so huge, is that there *is* a loop with the power company.
The loop starts with electrons being pulled from the ground, which then go over the three hot wires where one of those three hot phases is sent to your transformer primary, where the second lead of the transformer primary goes into the ground, which completes the circuit.
The fact that the earth is so huge that this completion of the circuit isn't even noticed back at the power company doesn't mean there isn't a loop.
It's just that the loop is one huge chunk of conductor (namely, the earth itself).
But, it's my understanding that this still completes the loop.
For example, if I lifted the transformer primary wire so that it no longer contacted the ground, that would immediately stop the current that flows back into the ground, hence breaking the loop.
Right?
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On Monday, November 25, 2013 3:13:56 AM UTC-5, Danny D'Amico wrote:

I do want to thank those who responded to my initial question about how the center tap gets referenced to ground.
I think we get sidetracked with the use of phase to mean two different thin gs. What if you put ground on the bottom of the secondary instead of the c enter? Hee, hee.
But, at the risk of another rabbit hole, electrons don't actually get pulle d from ground and sent to your house, unless you have a DC supply. In AC, e lectrons merely bounce back and forth a short distance, like a millionth of a meter. The wave travels, but not the electrons. IIRC.
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On Mon, 25 Nov 2013 06:38:36 -0800, TimR wrote:

This is a good thought-provoking point.
The electrons do get bounced back and forth, but, isn't there "current" in so much that *work* is being done, which requires the electrons to actually "move"?
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On Mon, 25 Nov 2013 21:25:05 +0000 (UTC), Danny D'Amico

Ah, so AC power doesn't work? It's good to find that out after 40 years as an electrical engineer. ;-)
The work is being done by the "wave". They do move, just not very far. They make up for being home bodies (though it's more than a few micrometers, IIRC) by their numbers. These numbers are fairy easy to calculate but not tonight. ;-)
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Read until you get to semi-conductors. Then read again:
http://www.allaboutcircuits.com/vol_1/index.html
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On Mon, 25 Nov 2013 19:54:22 -0600, Nightcrawler® wrote:

This reference from Smith College, Northampton, MA: http://www.science.smith.edu/~jcardell/Courses/EGR220/ElecPwr_HSW.html
Says: "The power company essentially uses the earth as one of the wires in the power system. The earth is a pretty good conductor and it is huge, so it makes a good return path for electrons."
That's from an EE class: http://www.science.smith.edu/~jcardell/Courses/EGR220/ EGR 220, Spring 2013, Engineering Circuit Theory
Taught by Judith Cardell, who researches this stuff: http://www.science.smith.edu/~jcardell/
She should know, shouldn't she?
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On Sat, 23 Nov 2013 10:17:08 +1100, John G wrote:

That's not how I understand it.
Even though the ground is so big that even all the nuclear power plants in the world pumping electrons into the ground couldn't change its potential, that doesn't mean that the ground doesn't complete the circuit.
If the power company chose any other conductor other than "the" ground, then they would have to have a wire for each phase distributed.
Since the power company chose to use "the" ground as "their" ground, the way I understand it, "my" ground is connected to "their" ground, so, the electron that flows into the primary of my transformer came from the ground at the power plant, and it goes back into the ground at my house, to (theoretically) make it back to the power plant.
Of course, the ground is so big that it's like pouring a glass of water into the ocean, where that molecule eventually will make it around the earth - but the immensity of the ground should not be construed as implying there isn't a loop from the earth at the power company to the wires to my transformer primary to the earth at my transformer.
At least that's how *I* understand the typical mains power in the US.
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Danny D'Amico explained on 25/11/2013 :

AGAIN I tell you the ground has no part in the supply of power it all happens on the wires and the ground is just the background.
Please got to school and learn the basic principles. :-?
--
John G



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On Mon, 25 Nov 2013 21:21:04 +1100, John G wrote:

Heh heh ... Let's just agree to disagree. :)
I understand your argument, and you understand mine.
I'm saying the earth can be thought of correctly either as zero potential, or, as an absolutely humongous conductor back to the power company.
Both explanations work just fine: - For you, you prefer to think of the earth as absolute zero potential. - For me, I prefer to think of the earth as the return path to the power supply.
Both are perfectly valid, so, my only objection is you telling me that I don't understand.
I'd be perfectly happy to be wrong, but, I think I *do* understand your point (and I agree with you); but I think you don't agree with me. So, we'll never get anywhere under those circumstances.
So, let's just agree that I think you're right and I think I'm right, and that you think you're right and that I'm wrong. That's OK.
BTW, a thought-provoking question would be: Q: Where do you think the power company gets its electrons from anyway?
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