Re: Does the earth "complete the circuit" to become ground?
From: w_tom (w_tom1_at_hotmail.com)
Date: 12/10/04
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Date: Fri, 10 Dec 2004 06:22:55 -0500
Look at high voltage transmission towers. Where is the
neutral? Each power circuit is composed of three 'hot' wires.
When at a substation, then three hot wires 'excite' wires on
other side of that transformer. There is no direct
connection. To understand how electricity gets from generator
to that transformer, it arrives as voltage between three 'hot'
wire phases.
Each phase is a sine wave. Each phase is 1/3rd of 360
degrees delayed from the next. A transformer can get voltage
when connected between two hot wires from the generator. Yes
it does get a wee more complex. Best to seek pictures of Wye
and Delta connections before the 'wee more complex' details
are discussed.
Generator outputs three sine waves - each delayed by 5.55
milliseconds (for 60 cycle power). All three are hot. There
is no return or neutral from generator to substation.
The word transmit or conductive return means same here.
Using earth as a return to a generator would create
unacceptable losses for same reason as explained in telegraph
/ telephone example. Generator connects to primary side of
transformer completely different from how secondary side of
transformer connects to the house and earth ground.
Furthermore 'ground' is confusing. Which ground? Earth
ground is only one ground in an electrical system.
Apparently your questions may be based upon what you are
looking at. What is it you see? That would better help
others to more accurately describe what currently you see and
are confused about.
"Thomas G. Marshall" wrote:
> w_tom coughed up:
>> No. Wires from power plant do not connect to your
>> building. There is no neutral wire leaving the power plant.
>> Your building is galvanically isolated from the power plant.
>> This was explained in previous posts. Earth ground (one of
>> many different grounds) does not become the conductor as also
>> explained in a previous post:
>>> Earth is not used by AC electric generators to transmit
>>> electricity for same reason.
>
> But this itself is vague. It says /transmit/. I was referring
> to simply using the ground as a return.
>
> And besides, R. Steve Walz just got done telling me:
>
> R. Steve Walz:
> If you drag around the hot, you have to drag
> around the neutral, or have a damned good
> ground stake.
>
> This implies what then? That either:
>
> 1. the generator is sending two wires
> or
> 2. the generator is sending one wire, and the ground is the
> return to the generator(?)
>
> The generators I've fooled around with always have two leads, just
> like a battery does. Where does that neutral lead of the power
> plant generator go. To the earth?
>
>> In the case of an electric
>>> system, where you find a transformer, instead think of that
>>> transformer as a battery (an AC battery). Then forget about
>>> everything from that transformer back to generator. You are
>>> now ready to discuss earthing from the perspective of that
>>> circuit.
>>
>> To understand the circuit, think of that utility pole
>> transformer as a battery. Pretend there is no other
>> connection. Pretend that utility pole 'battery' provides all
>> the power to you building. Now you are ready to understand
>> how your AC electricity works, and how earthing and other
>> different grounds works.
>
> Yep, that part was explained already. I'm trying to phathom the
> generator part now.
>
> That's fairly easy to understand. What I don't understand is how
> that "battery" can be fed by only a hot wire from the generator.
> How is that circuit completd?
>
>> You are confusing earth with ground. Earth is one type of
>> ground. A long previous post explained this in detail. Your
>> car, computer chassis, etc. have no earth ground. They have
>> other grounds (car chassis ground, household safety ground,
>> etc) Only some grounds have a connection to earth ground.
>>
>> They are grounds - car chassis ground (which has no connection
> to earth ground), safety ground, logic ground, floating power
>> supply ground (which also has no earth ground connection)
>> etc. Many electrically different grounds that can be
>> interconnected - but remain different and separate grounds.
>
> Yes, yes, yes, I understand all that. I've done car wiring, pc
> wiring, and even wired up counters using all TTL.
>
> But given that you need to *always* complete a circuit, how is
> the circuit completed from, say, a diesel generator at the plant
> outward to that transformer on the pole.
>
> A generator has two leads. One for power and one for.....the return?
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