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

[TimR]

Thanks everybody, that was very helpful.

[trader4]

e:

to that transformer? If it is 3 phase leg to neutral on the primary side, then the center tap should be above neutral on the secondary (house) side, right? Which would mean that house neutral is NOT at ground level. But I 'm pretty sure it is.

an example. Which two wires do we use? You only have the choice of leg t o leg, or leg to neutral.

e 240 volts line to line. Then center tap it, and you get 120 from each li ne to center.

So you too believe that the same amount of power that's delivered by 3 wire s with 3 phase would require 6 wires, twice the amount of copper to deliver any other way?

Remember when you insisted that it was illegal for employers to help pay for their employees Obamacare? Made an ass out of you on that one.

Remember when you didn't know the difference between how a 4 wire oven and a 3 wire is hooked up? Even with RBM, Bud and I all telling you that you were wrong. Made an ass of you on that one too.

And now we have your insistence that the two legs of a 240V service are not 180 deg out of phase. That no such usage of the wording would ever be used in engineering.

Well, here it is, from the IEEE. A paper delivered at a conference for power systems engineers:

4520128

Distribution engineers have treated the standard "singlephase" distribution transformer connection as single phase because from the primary side of th e transformer these connections are single phase and in the case of standar d rural distribution single phase line to ground. However, with the advent of detailed circuit modeling we are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary. Whic h now brings into focus the reality that standard 120/240 secondary systems are not single phase line to ground systems, instead they are three wire s ystems with two phases and one ground wires. Further, the standard 120/240 secondary is different from the two phase primary system in that the second ary phases are separated by 180 degrees instead of three phases separated b y 120 degrees.

There it is folks, in context, about the very specific point that krw claims is a lie.

Here's the essential cliff notes version, just for you krw:

"Which now brings into focus the reality that standard 120/240 secondary sy stems are not single phase line to ground systems, instead they are three w ire systems with two phases and one ground wires."

That's from an engineering paper presented at an IEEE conference. I suppose they are all idiots, liars, etc too, because they recognize that you have two phases that are 180 deg apart.

But keep digging your fools hole deeper if you like.

[krw]

Wrong.

No, unlike the stupid lying ass, Trader, I know the difference.

[trader4]

Here, so everyone can see who's a liar and who knows what they are talking about. From the IEEE (Institute of Electrical and Electronic Engineers), a paper delivered at a rural electric power conference:

"Distribution engineers have treated the standard "singlephase" distributio n transformer connection as single phase because from the primary side of t he transformer these connections are single phase and in the case of standa rd rural distribution single phase line to ground. However, with the advent of detailed circuit modeling we are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary. Whi ch now brings into focus the reality that standard 120/240 secondary system s are not single phase line to ground systems, instead they are three wire systems with two phases and one ground wires. Further, the standard 120/240 secondary is different from the two phase primary system in that the secon dary phases are separated by 180 degrees instead of three phases separated by 120 degrees. "

Anyone following the discussion can read it and see that the IEEE engineers are saying EXACTLY what I've been saying all along. It couldn't be any more specific and on point. That IEEE paper is

100% in agreement with everything I've said. Of course krw will snip it and ignore it, instead of learning.

[trader4]

And note what else it says. It has one hot leg labled "Phase A", the other "Phase B". That means there are two phases present. Next, look at the note: "The phase of hot leg 2 (Phase B) is in the opposite direction, ie 180 degrees apart from the phase of hot leg 1 (Phase A)."

Perhaps you can explain it now to krw that this document clearly shows two phases present and that they are 180 deg out of phase with each other. It's precisely in agreement with what I've been saying for two days now.

[krw]

Stop lying, Trader, and LEARN TO READ.

[makolber]

Here's what I'm not getting at the moment. What are the connections to tha t transformer? If it is 3 phase leg to neutral on the primary side, then th e center tap should be above neutral on the secondary (house) side, right? Which would mean that house neutral is NOT at ground level. But I'm pretty sure it is.

your confusion is becasue you don't understand how a transformer works. Th e pri and secondary are isolated from each other. The center tap of the se c has NO RELATIONSHIP to the primary. Think of the secondary as seperate f loating power supply not related to the primary. The center tap of the sec ondary is neutral or ground ONLY becasue it gets connected to ground. Sinc e it is connected to ground the two ends become +120 and -120 relative to n eutral.

Mark

[trader4]

to each other

d by 3 sets of coils at the power plant).

Yes you have to snip them because they are irrefutable and show that you;re wrong.

Typical, more name calling when you've lost an argument. Is the IEEE lying too? Here from the peer reviewed IEEE, a paper presented at a conference of power engineers:

4520128

"Distribution engineers have treated the standard "singlephase" distributio n transformer connection as single phase because from the primary side of t he transformer these connections are single phase and in the case of standa rd rural distribution single phase line to ground. However, with the advent of detailed circuit modeling we are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary. Whi ch now brings into focus the reality that standard 120/240 secondary system s are not single phase line to ground systems, instead they are three wire systems with two phases and one ground wires. Further, the standard 120/240 secondary is different from the two phase primary system in that the secon dary phases are separated by 180 degrees instead of three phases separated by 120 degrees. "

Or how about this:

A split-phase (240/120V) power system is a 3-wire, single-phase, mid-point neutral system, which consists of two 120V "voltage sources"; connected out

-of-phase by 180 electrical degrees with a neutral connection between them.

Or this:

"The phase of hot leg 2 (phase B) is in the opposite direction, ie 180 deg apart from the phase of hot leg 1 (phase A)"

"The secondary of the distribution transformer has a grounded center tap and is wound in a manner that supplies two 120V AC phases which are 180 deg out of phase with each other (split phases)"

They even go on to talk about using a oscilloscopet to look at them and say:

"This indicates that the two 120V AC voltages are 180 deg out of phase"

Go ahead, snip those truths too and keep making an ass of yourself.

[nestork]

Mark:

I find the first diagram on this web page that was posted by SRN helpful:

It shows the primary side of the distribution transformer connected between the 7200 VAC carried by the single phase wire and ground.

What I can't figure out here, tho, is that if the distribution transformer on the telephone pole is connected to ground, then it's connected via the ground wire that goes down the pole and is wrapped around the base of the telephone pole. So far as I know, that ground wire is not insulated, so that anyone that touches that ground wire would get a 7200 volt shock, which would surely kill them.

So, I think that wiring diagram is mostly correct, but I think there's a problem with the primary side of the transformer connected to ground via the telephone pole's grounding wire.

[trader4]

Don't let krw see that. The reference clearly says that with a spit-phase 240v/120v service, there are two phases present and they differ by 180 degrees. He says that just can't be.

Even if it were only connected that way, you would only get a shock if the ground wire were broken and you grabbed the energized end. Otherwise if you grabbed an intact wire, the only voltage present would be whatever there is due to the small resistance of the wire, which would result in a small voltage drop across the wire run. The 7200 volts is across the transformer. The 25 ft of copper wire only drops a few volts, depending on the current flowing in it and the resistance of the wire.

Actually the transformer is typically connected to a primary neutral. The primary neutral is in turn connected to ground much like on the secondary (house) side. It's not necessarily at every transformer, but periodically along the run. Other transformers connected to the same neutral, but from different phases, will balance out and reduce the current flowing in the neutral.

Yes, IMO, they should have shown the primary connected to a neutral, not just ground.

[makolber]

ment. What are the connections to > that transformer? If it is 3 phase leg to neutral on the primary side, > then the center tap should be above neutr al on the secondary (house) > side, right? Which would mean that house neut ral is NOT at ground level. > But I'm pretty sure it is. > > your confusion is becasue you don't understand how a transformer works. > The pri and sec ondary are isolated from each other. The center tap of > the sec has NO REL ATIONSHIP to the primary. Think of the secondary as > seperate floating pow er supply not related to the primary. The center > tap of the secondary is neutral or ground ONLY becasue it gets connected > to ground. Since it is c onnected to ground the two ends become +120 and > -120 relative to neutral. > > Mark Mark: I find the first diagram on this web page that was posted b y SRN helpful:

It shows the primary side of the distribution transformer connected between the 7200 VAC carried by the sing le phase wire and ground. What I can't figure out here, tho, is that if the distribution transformer on the telephone pole is connected to ground, the n it's connected via the ground wire that goes down the pole and is wrapped around the base of the telephone pole. So far as I know, that ground wire is not insulated, so that anyone that touches that ground wire would get a

7200 volt shock, which would surely kill them. So, I think that wiring diag ram is mostly correct, but I think there's a problem with the primary side of the transformer connected to ground via the telephone pole's grounding w ire. -- nestork

OK..

in the diagram, the top of the primary is connected to 7200Volts and the bo ttom of the primary is connected to ground. THe voltage on the wire connec ted to ground is close to 0. It doesn't matter that some of the current pa ssing through that wire started out at 7200 Volts. As long as the wire is connected to ground, it is ground. So someone can touch that wire with no problem.

BUT.. if the ground connection to the wire should come loose, then the wire will have a high voltage on it and would be dangerous, becuase it has curr ent in it "that is trying to get to ground" and can't.

That is actually the same danger in the 3 wire dreyer circuit. The ground and neutral share the same wire and if the connection to that wire comes lo ose, the "ground wire" will have dangerous voltage on it.

On the pole transformer, ther bottom side of the primary coil is connected to ground, but the wire you see running down the pole is NOT the ONLY conne ction to ground. All the grounds in the entire distribution system are con nected together so if the ground to one particular pole should come loose, the wire is still probably at ground due to all the other connections. But if I saw a loose ground wire running down a pole, I still would not want t o touch it.

Mark

[nestork]

Mark:

But, if what you're saying is true, then there is power flowing to ground through the primary coil of every distribution transformer in the USA and Canada 24 hours per day, 7 days per week, 365 days per year.

And, with a voltage of 7200 volts driving that current, it would seem to me there would be a significant current flowing in the 40 or 50 foot cable going down from the transformer to the ground.

Why don't those cables get warm to the touch?

Is it entirely the impedance of the primary coil in the transformer? There is a 24 VAC doorbell transformer in every house in the USA and Canada. 120 Volt power is flowing through the primary coil of those transformers 24/7/365 and yet no one seems to be concerned about that power wastage. And, the only thing that makes sense here is that the impedance of the primary coil is so high that the current flow to ground is actually very small. Ditto for household transformers.

[Nightcrawler®]

They used to provide a protective cover for the transformer ground. In the old days it was a U-shaped channel milled out of wood.

[trader4]

All the power isn't flowing in those ground wires. You typically have a neutral that is shared by multiple transformers. Each transformer isn't connected to the same phase, they are connected to phases in a distributed fashion. That means that the current in the neutral is only the unbalanced portion. If you had 3 transformers for 3 groups of houses, each on a seperate primary phase, with equal loads, the neutral current would sum to zero.

And then you have the neutral grounded periodically along it's run, with a heavy, properly sized, ground wire, capable of handling the current through it.

[Danny D'Amico]

For some reason, I didn't see this thread, and assumed it hadn't posted. So I apologize for not having answered any issues.

I've learned a lot.

For example, the ground and the neutral, in my house, are connected together in the main panel, but not in the sub panels.

I've learned the neutrals are different than grounds in other ways. For example, they never branch (they always stay with their associated hot wires). They only meet at the main breaker panel.

The grounds, on the other hand, go all over the place. Plus, most of the time, they're not insulated (although they may also be green).

[Danny D'Amico]

Here's a PNG of that diagram, for reference:

In the dryer thread, it was noted that most USA circuit breakers are *not* arrayed in AB-AB-AB format; but in AA-BB-AA-BB format.

I'm not sure what that means though...

[Danny D'Amico]

Here are six distribution wires, by the way ... :)

[Danny D'Amico]

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! :)

[Danny D'Amico]

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).

[trader4]

It's referring to where the two legs/phases show up in the panel. But, I'm not sure what AB means either. You need to define what the perspective is. Just saying AB is meaningless, because it could mean A is on the left, B on the right, or it could mean A is above, B is just below it. In any case, what you have, is the latter. That is what is shown in your diagram. Otherwise you would get zero from a double pole breaker instead of 240V.