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

[trader4]

You just keep harping back to the same thing. You're asking for us to prove a negative. And what is really annoying, is that you're so lazy that you refuse to educate yourself or listen to everyone else here, who knows a lot more. You didn't know the difference between a neutral and a ground at your house. You still don't understand the concept of a neutral, a ground, the difference, on the PRIMARY side. Neither, apparently does the author of the "How things work piece". That same exact verbage is in ALL the references you've found, cut and pasted, or even directly referred back to, yet you keep claiming you have 6 references. In fact, all you've got is one reference from a very elementary description, and it's wrong.

I've pointed out several times now, that the same reference, just a couple sentences earlier, says that the power plant has 3 phase wires, plus a "neutral or ground". If that's true, then why do you need the earth as a return path? That statement also shows that the author doesn't know the difference between a neutral and a ground. Yet, you don't address that, don't respond to it, just ignore it. Why is that?

I've also tried to educate you on 3 phase power and why those 3 wires alone are all it takes to deliver power. Those of us familiar with 3 phase see 3 wires running down a transmission line and know how the power flows, that just those 3 wires allow the power to flow, no separate earth return is needed. It's shown here in an animated figure, which I also provided previously:

Three wires deliver the power. Now explain to us why you need the earth for a return path? Not understanding 3 phase, you believe the current needs an earth return, instead of flowing back on the same 3 wires. And instead of learning, you insist that we do your research for you.

[Danny D'Amico]

:)

I won't go into a discussion of how facts at a junior college are any different than facts at a high school or university, or even those same facts at the power company (the references I cited were from industry also), simply because, I'll lose any argument like that on the net due to the old adage...

And, I'll stop asking for references that state the currents *don't* go back to the power company transformers through the ground...

I will simply continue to locate, read, and quote sources that explain the return path for current, back to the power company's transformers.

The more I read, the more I find that this return path is not straightforward.

There are local loops, where the math can get complex, so, I'm trying to unwind this wye-versus-delta thing as we speak ...

Here's a good starter paper on what those ground paths back to the power supply transformers looks like that I am still reading with great interest:

That's from a company that makes isolation transformers, so, they're not "junior college" level, right?

[trader4]

Again, the disagreement started when the simple statement was made that the two hot legs on a 240v/120v service are 180 deg OUT OF PHASE WITH EACH OTHER. That is absolutely true. The discussion was *not* about what it's called. And technically, it's called a "split-phase service".

I'm still waiting for even one of you alleged experts to give us your definition of "phase" in electrical engineering.

[Danny D'Amico]

heh heh ... rather than supply a reference, another guy also attacked the credentials of the many references providing, implying, essentially, that facts taught at a junior college are essentially wrong, simply because it's not a four-year college.

And, now you bring up SWERT, which also has nothing to do with the question of typical power distribution in the United States, since neither you nor I are getting our household power through SWERT.

Let's keep SWERT out of this because the entire discussion is about the typical US power distribution system, which is basically how we're getting the electrons to do this typing at our keyboards.

Also, let's not try to prove our points simply by stating that the reference is wrong because it's from a junior college or that the answer is simplified so therefore it must be wrong.

The statement the professor made is simplified, but, it's not untrue because it's simplified.

The class teaches students: "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."

Anyway, I'll stop asking for a reference that shows otherwise.

What I'll do is continue to try to understand the typical power distribution scheme in the United States, with your help.

[trader4]

Oh my lying eyes. I must be hallucinating when I see all those bare service neutrals run to houses. Or all those base primary neutrals I see on poles going down the road.....

[Danny D'Amico]

Indeed. The return path to the power company's transformers is complex.

I've found a few references that try to explain it (some of which are on google books, so I can never tell if you'll see the same pages that I do).

The math is horrendously complex.

But the summary is simple: "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."

Anyway, I'm moving on to trying to understand *why* and *when* the power companies use the wye versus the delta transformers ...

I'm starting with the *simplified* answer, and then working toward the key details:

"Three-phase power is most commonly provided by the electric utility in a wye configuration. The main advantage to wye power is that the phase-to-neutral voltage is equal on all three legs."

[jamesgang]

Hell, the hots on poles are bare too pretty much everywhere.

[trader4]

Sigh.... The same "How stuff works" reference is still that one source, no matter how many times various people use it. And it's wrong.

All I see at that link is a course outline, nothing that addresses the earth return issue.

When you have a link that shows that, I'll be happy to look at it.

[trader4]

Good grief. Now I get it. A college course has a link to that same one reference "How stuff works", and that makes it right? Every single "reference" you keep coming up with, points right back to there. It's quite possible the associate professor didn't even fully read the thing. And you have to wonder about any college course that uses "How stuff works"

[trader4]

Uh, no, it's worse than that. His one reference is the creator of "How stuff works". He justs keeps googling and finding the exact same verbage or a direct link back to that, and then he counts it as a new, independent "reference". Unless I missed something, I think he's showing tht ap Cardell referenced the "how stuff works" description in her course.

He refuses to even acknowledge the links that you provided that talk about how systems are grounded, what the earth is used for, etc. And he's too lazy to spend an hour learning how 3 phase works and why you only need those 3 wires to transmit power.

[trader4]

What references from industry? Every "reference" you have that I've seen uses the same exact verbage from "How stuff works" or is in fact a direct link back to it. One place that got it wrong, cited 10 times, doesn't make it right.

Actually it is. See the Wikipedia diagram I gave you a link to twice now:

It shows power coming and going on just 3 wires, no planet earth required. That simple animation shows how it works. Look at that and tell us why another path is needed.

No and there isn't anything there that says power plants use the earth as a return path. It's all consistent with what everyone here has been telling you.

[trader4]

Claire provided you with reference that talk about grounding power systems. They don't talk about the earth being used as part of the power flow path.

And again, ALL your references are straight back to the one "How stuff works", which has it wrong. Citing the same thing 10 times doesn't make it right.

Good grief. It directly addresses the issue. They talk about using the earth as a return path in special cases, eg isolated rural areas in AU. And they give a list of problems with it, why it's the exceptional case.

Fine, so then we're back to you being wrong.

Where is the link to what the prof actually said? Or is it like I think it is, that she's just using a link to "How stuff works?"

Look at the Wikipedia animation.

Case closed.

[trader4]

If you post that same verbage from "How stuff works", one more time, we're all going to throw up.

Hopeless.

[jamesgang]

The earth is not a power path. Period.

[Wild_Bill]

I don't see the earlier comment, but from the links and the search question, I presume the conversation was about a circuit term referred to as "return".

A lot f folks are fixated on naming one power lead as "return", when there is nothng related to any sort of "return" taking place in a circuit.

There are 2 conductors.. and one is a higher potential than the other. That's all there is to it, but you'll probably never fnd ths statement in any text book.

The power is disspated at the load, and there is nothing to return to any other location.

I don't know where the fantasy of a return originated, but there is none iin an electrical circuit. Hydraulic circuit, yes, thre is generally always a return line.. for obvious reasons.

The earth, meaning the planet, is not half of an electrical crcuit.. with maybe one exception being lightning strikes. Hills and terrain affect RF energy, and the ground/earth at the base of an antenna is often imbedded with conductors to form a ground plane.

Electrical circuts deliver power to an appliance, tool, light bulb etc as the two differing potentials, and the power is disspated as heat, light, motion etc at the device beng powered.

It is aburd to belive that power is returned thru many miles of distribution gear and back to the generation source, or that it's returned thru the soil. Yet, the majorty of folks believe and continue to express/repeat this concept.

[Ralph Mowery]

It is not straight forward. It zig zags.

No joke, look up zig zag transformer.

[bud--]

It is fatally flawed, as described in another post.

It is not from an EE class.

It is something Smith College picked up from somewhere. As far is I know it was not written by anyone ever associated with the college.

What should she know? She didn't write the piece at the top.

Why does everyone who understands power distribution disagree with you?

[bud--]

As trader noted, the author says "there are four wires coming out of every power plant: the three phases plus a neutral or ground common to all three."

The 4th wire is a neutral, which is grounded.

The author has a problem of identifying neutrals as grounds throughout the piece.

Nowhere does the author describe how earth is used as a conductor in power transmission.

------------------------ "The fourth wire lower on the poles is the ground wire"

The 4th wire is a neutral which is earthed.

-------------------------- "Past a typical house runs a set of poles with one phase of power (at

7,200 volts) and a ground wire (although sometimes there will be two or three phases on the pole, depending on where the house is located in the distribution grid)."

The "ground wire" is in fact a neutral wire (which is earthed).

-------------------------- "There are two things to notice in this picture: There is a bare wire running down the pole. This is a grounding wire. Every utility pole on the planet has one."

Actually every utility pole does not have one. With the overhead distribution in Minneapolis poles with transformers have an earthing wire. Other poles may or may not have one.

--------------------- Continuing "If you examine a pole carefully, you will see that the ground wire running between poles (and often the guy wires) are attached to this direct connection to ground."

The wire is a neutral that is earthed.

The distribution voltage in my area has one of the 3-phase wires tapped off the distribution and feeding 4-8 blocks. The 3-phase neutral is tapped off the supply neutral at the same place and runs with the phase wire. As above, the neutral is earthed at multiple locations. The same primary neutral is used as the secondary neutral, and so the secondary neutral at the transformer is earthed.

------------------------------- Continuing "There are two wires running out of the transformer and three wires running to the house. The two from the transformer are insulated, and the third one is bare. The bare wire is the ground wire."

As about everyone here knows, the 3rd wire is a neutral, not a ground.

------------------------------- There is an electrical diagram of a transformer with the secondary center tap labeled "ground".

Also is obviously a neutral.

-------------------------------- There are multiple pictures of distribution lines, all of which have a neutral. Sometimes the author misidentifies the neutral as "ground". Transmission lines also have a neutral. Sometimes it is run on the top for lightning strikes.

---------------------------- "When a 120-volt power line connects directly to ground, its goal in life is to pump as much electricity as possible through the connection."

The electricity does not flow to earth. It returns to the utility transformer through the N-G bond at the service and through the service neutral wire.

------------------------------- The author consistently misidentifies neutral wires as "ground" wires. His pictures show neutrals along with distribution wires. He does not explain how the earth is used in power distribution. He does not appear to understand power distribution.

This piece is fatally flawed.

[gfretwell]

An interesting thing for me was I still had current in my ground electrode conductor with the service disconnect open. My ground electrode was actually sinking unbalanced current from the pole.

Like the old adage says, current doesn't take the path of least resistance, it takes ALL paths.

[bud--]

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.