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Neutral and phase.

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electricity86

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The neutral is usually connected to earth, whether on the electicity company, or inside the wall at our homes.

We therefore treat the neutral as ground (0V reference).
Is it correct to say that:
- When the current is possitive - the upper half of the sine wave - then electrons move from neutral to phase.
- when current is negative - lower half of sine wave - electrons move from phase to neutral.

When the neutral is connected to earth, then how come it can source electrons during the half sine wave?
 

Sceadwian

Banned
The electron flow during postive/negative phase is correct.

The reason you can get some slight current between neutral and ground is because each outlet in a house is part of a branch. Electricty flowing through any other part of the branch is going to produce a slight voltage in the neutral wire due to the resistance of the wire (no matter how small) alternatly if the neutral is grounded at same the pole or the power plant not directly at the breaker box in the house there's going to be a slight difference between the two grounds.
 
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MikeMl

Well-Known Member
Most Helpful Member
The electron flow during postive/negative phase is correct.

The reason you can get some slight current between neutral and ground is because each outlet in a house is part of a branch...
That's not what the OP asked about. His question was about current flow from L1(which he called "phase") to N.

For the purpose of this discussion, N is always 0V. During the time when L1 is NEGATIVE with respect to N, electrons flow from L1 toward N (electrons always swim upstream :D)

When L1 is POSITIVE with respect to N, electrons flow from N to L1.

btw- Conventional current (the kind you read about in textbooks and engineers talk about) always flows from POSITIVE to NEGATIVE. I wish people would forget all about electrons carrying charge...
 
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Sceadwian

Banned
I told him the electron flow directions he stated was correct.
- When the current is possitive - the upper half of the sine wave - then electrons move from neutral to phase.
This is 100% true. That is the direction of the electron flow.

- when current is negative - lower half of sine wave - electrons move from phase to neutral.
This is also 100% true. That is the direction of the electron flow.

Now that I re-read it the last question doesn't make sense.
When the neutral is connected to earth, then how come it can source electrons during the half sine wave?
In the stated example neutral and ground are the same thing there is no difference so tieing neutral and ground together will not affect anything as they're already the same. I was thinking real world with the neutral never being quiet the same as ground.
 
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MikeMl

Well-Known Member
Most Helpful Member
...
Now that I re-read it the last question doesn't make sense.
In the stated example neutral and ground are the same thing there is no difference so tieing neutral and ground together will not affect anything as they're already the same. ...
The OP was confused about current flowing between two electrical nodes that have different potentials.

His confusion is evidenced by the following statement:
"When the neutral is connected to earth, then how come it can source electrons during the half sine wave?"
 
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Sceadwian

Banned
The reason for that confusion confuses me =)
 

crutschow

Well-Known Member
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When the neutral is connected to earth, then how come it can source electrons during the half sine wave?
Whether the neutral is connected to earth or not makes no difference. The earth doesn't source the electrons, the neutral wire going to the transformer supplies the electrons. The earth is just sitting there, providing a ground reference for the line.
 

Sceadwian

Banned
Crut, if the earth is grounded at the same point the neutral is grounded your assumption is wrong. The Earth and the Neutral simply become the same point.
 

electricity86

New Member
Hey guys and thank you very much for your answers.
First, I'm glad you confirmed what I said regarding current'd direction.

When I ask how come the Neutral, which is connected to earth, can source electrns during half cycle of sine waveform, I meant to the possitive half where V_phase is larger than V_neutral (earlier you approved that in this possitive half, electrons flow from N to L1).

crutschow, I understand my mistake, its the transfomer's Neutral end that sources the electrons (just like the transformer's L1 end).
If Earth is connected to N, and electrons flow through the N wire, they dont flow also through EARTH on their way to the load?
 

electricity86

New Member
The electron flow during postive/negative phase is correct.

The reason you can get some slight current between neutral and ground is because each outlet in a house is part of a branch. Electricty flowing through any other part of the branch is going to produce a slight voltage in the neutral wire due to the resistance of the wire (no matter how small) alternatly if the neutral is grounded at same the pole or the power plant not directly at the breaker box in the house there's going to be a slight difference between the two grounds.
I didnt quite understand what two grounds are you talking about? N and Earth? or the beginning of N's wire at the power company and the end of N's wire at outlets at our homes?
 

Sceadwian

Banned
I didnt quite understand what two grounds are you talking about? N and Earth? or the beginning of N's wire at the power company and the end of N's wire at outlets at our homes?
If N is grounded at the junction box N and outlet Gnd are the same thing, except the bulk majority of the current is being drawn in/out of the the N wire, the Gnd wire is left 'unloaded' Use a multimeter set to measure AC between the GND and Neutral of any household circuit that's loaded and you'll see a voltage potential guaranteed.

If Neutral is grounded only at the power station and not locally there will still be a difference in the local ground and the substation, they're never exactly the same over any significant distance. Without a local ground reference though the potential will likely be bigger.

These are practical considerations not theoretical ones. The real world puts theory to shame.
 
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Nigel Goodwin

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Hey guys and thank you very much for your answers.
First, I'm glad you confirmed what I said regarding current'd direction.

When I ask how come the Neutral, which is connected to earth, can source electrns during half cycle of sine waveform, I meant to the possitive half where V_phase is larger than V_neutral (earlier you approved that in this possitive half, electrons flow from N to L1).

crutschow, I understand my mistake, its the transfomer's Neutral end that sources the electrons (just like the transformer's L1 end).
If Earth is connected to N, and electrons flow through the N wire, they dont flow also through EARTH on their way to the load?
I would strongly suggest you stop confusing yourself by talking about electrons, it doesn't really help at all.
 

RODALCO

Well-Known Member
Generally the utilities have two systems in different parts of the world.

1 The M.E.N. system (Multiple Earth Neutral System) Used in most British countries e.g. U.K. New Zealand, Australia.
Here are the Neutral and Earth tied together at the star point of the distribution transformer, at distribution pillars and the switchboard of the consumer. The voltage between the two is minimal except when a neutral conductor is broken, the earth wire will carry the return current to the star point of the TX. Earth rods are required also in this case

2. The System where the Earth is not connected to the neutral. used in most European Countries. The neutral can carry a voltage of a couple of volts, depending upon the loading drawn by the circuit.
The Earth at the installation is on Earth rods and earth rods at the distribution TX, these are not tied to the Neutral point.

It depends how well balanced the load is if a Neutral carries current or not.
 

crutschow

Well-Known Member
Most Helpful Member
If Earth is connected to N, and electrons flow through the N wire, they dont flow also through EARTH on their way to the load?
If the neutral only connects to earth at one point, the answer is no.
 

electricity86

New Member
Thanks alot friends.

If I understood correctly, there are the next two options and they go like that:



If its correct, then something is not quite understood in the upper case (Earth's connected to N also in swithboard).
If the current flows back to or from the electricity power, the voltage of the N's end in the switchboard side wouldnt be 0V, but V_L1*sin(ωt)/(Load+R_parasitic)*R_parasitic (voltage divider forumula).
How is it settled then?
 

electricity86

New Member
It was said here that if the earth is also connected to the neutral in the switchboard, then the netral voltage is minimal and close to 0V, which is the earth's voltgae.

As you can see in the bellow picture, which i fixed, the neutral voltage stays the same when Earth is connected to it in swithboard and when isnt.

So how come connecting the Earth to the neutral in switchboard helps reducing the neutral voltage at our outlets?

 

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unclejed613

Well-Known Member
Most Helpful Member
most 3-phase systems are ground (or earth) independent, if they're delta-wired (windings wired in a Δ). at the transmission end and at the user end, they are converted using transformers to a wye (the configuration of the windings resembles a Y ) configuration with 3 phases and a ground reference from the center of the Y. so at the generating station and at the termination they are Y wired, which has a ground reference. along the transmission lines they are Δ wired which is independent of ground.
 

electricity86

New Member
Thanks friend.
It still doesnt clarify what was said that connecting ground to N in switchboard reduces N's voltage.
Thats why i'm trying to figure out.
 
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