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Neutral and phase.

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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.

You've misunderstood was was said - the earth wiring inside the building is connected to the neutral wire, it's not earthed separately at both ends.

It's called a PME earth.
 
You've misunderstood was was said - the earth wiring inside the building is connected to the neutral wire, it's not earthed separately at both ends.

It's called a PME earth.

Thank you very much for correcting me.
So there is the first earth connected to N in the electricity company and there is the second earth connected to N at our homes, which differ from each other.
- Connecting the second earth to N at our homes helps reducing the N's voltage that differs from 0V since it has parasitic resistance?
- This second ground has the same potential as the first ground (first = in electricity company)? or is it lower/higher?

Thanks again.
 
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Not quote elec, the power companies neutral and the houses ground aren't actually directly connected. It's different in various parts of the world, but here in the US at least every house get's it's own transformer. The power companies hot and neutral wires go into the transformer and the house gets an isolated hot an neutral out. You can't leave a houses electrical system floating like that so the neutral line is grounded, either at the pole or the house (or both) I'm not quiet sure. So your diagram is missing the transformer.
 
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Not quote elec, the power companies neutral and the houses ground aren't actually directly connected. It's different in various parts of the world, but here in the US at least every house get's it's own transformer. The power companies hot and neutral wires go into the transformer and the house gets an isolated hot an neutral out. You can't leave a houses electrical system floating like that so the neutral line is grounded, either at the pole or the house (or both) I'm not quiet sure. So your diagram is missing the transformer.

Thanks!
I'll add the transfoermer to my notebook :)
When you say the pole, you mean the transformer's netural output right?

So grounding the netural either at pole or at home, does keep your neutral line from floating, but I dont think that it prevents from voltage loss on the wires, since the voltage loss happens between the Elec. comapany's neutral and transformer's netural input, is it right?
 
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Most devices will work +/- 10% of their rated working voltage so line losses are seldom a problem if the wiring is properly rated.
 
Thanks alot friend.

When the earth is not connected at the building, it means that the whole building doesnt have earthing?

If this is the case, then what is connected to the third,lower hole in the outlet at the building?
 
A totally separate ground wire. Usually they're long conductive rod(s) driven into the ground. Sometimes plates, I'm a little vague on the details of how to come up with a good electrical ground, mainly because it's highly dependent on the local geography and soil conditions.
 
A totally separate ground wire. Usually they're long conductive rod(s) driven into the ground. Sometimes plates, I'm a little vague on the details of how to come up with a good electrical ground, mainly because it's highly dependent on the local geography and soil conditions.

Thank you again Scedwian. :)
So there could be three different grounds envolved in this?
1. Earth that is connected to N in the electricity company.
2. Earth that is connected to N in the transformer's Neutral output.
3. Earth that is connected to the Earth hole of the outlet at home.

Is Earth #3 connected also to the N wire?
Since Earth #2 (if exists) is already connected to the N wire and keeps him from floating, i'm not sure if Earth #3 is connected to.

Thank you alot!
 
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Power stations do not transmit power (3 phase) + Neutral. Have a look at overhead long distance power lines. You will only see three sets of wires.

Once the high voltage lines (eg. 440KV) gets tapped down at substations, the transformers are wired Delta/Star. The Delta side is for the three Live wires. The Start side is for the lower voltages, where the start point acts as the neutral.

Power transmission
Three Phase Power
 
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shown is a quick crude drawing of what happens between the generator and your house. the thick lines are windings. the thin lines are wires.
 
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sorry, pic didnt upload.... lets try again
 

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sorry, pic didnt upload.... lets try again

Are you trying to show on your picture that the generator at the power station has a Neutral point connected to the star point of the transformer?

Sorry, I don’t agree with you. A motor can act as a generator. Do you connect neutral to a 3 phase motor? No. The same for the generator at the generation end. It does not have the neutral point. Neutral is only tapped out at the far end (domestic use for example) where a group of houses are connected as you indicate on your picture.

Load balancing plays a very important role in the distribution of power, but that’s far to technical for me to explain.
 
Thank you very much both of you.
reading your posts was really learnful.

SPDCHK, So what connects the generator at the electricity company to the ground?
It must have a reference point to ground, mustn't it?

You meant that its suppose to be like that?
actransmission-jpg.29730
 

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Well in the U.S the last transformer would be drawn a single phase, (split phase with center tap, 3 wires) output with two hots and one neutral. Potential between the two hots is nominally 220vac and potential from either hot to neutral is 120vac. Showing a Y output transformer winding is not correct for the common house U.S. installation.

Lefty
 
as i said, it's a crude drawing...... the generator could even be delta wired too (Tesla'a patent has it wired wye), but the distribution point and the transmission system was basically what i was getting at. the secondary of the distribution point doen't necessarily have to be a wye with a ground either, as each of the 3 windings could feed the primary of a split-single phase transformer, where the secondary of the split phase has a center tap which is the neutral for two 120V sections which are 180 degrees out of phase, giving 120V for each half, and 240V total between the hots. this is the standard house service.

3 phase service (for large offices and light to heavy industrial) takes the points of the wye (or star) as the 3 phases, and the center tap as neutral. there's 120V between each phase and neutral, and 208V between phases. the neutral is grounded at one place, at the "service entrance", there are special applications that use 3 phase delta transmission directly to the end user, one of which is the motors for driving pumps for sprinkler systems in high rise buildings (obviously this isn't at the normal voltages in the tens and hundreds of thousands of volts, but at the 480V that is used for the motors).
 
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It's normally connected to earth to prevent it floating at high voltages. Without an earth connection the 230V supply could float at any voltage, if someone connected a 10kV autotransformer to it and the secondary got shorted to earth, the mains would float at 10kV which would destroy the insulation and cause a fire.

Bonding ensures that the highest voltage relative to earth is the phase voltage.

The secondary of the distribution transformer could even be delta wound, a neutral point could be formed by a zigzag transformer placed nearer to where the load is. Delta is better than star for low voltages and high currents and zigzag transformer are good for harmonic reduction as well as creating a neutral point.
 
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