Difference between Neutral and Ground

roadey_carl

Joined Jun 5, 2009
125
Hello everyone!

I am an electrical engineer and I have a good knowledge of theory of circuits from theoretical point of view. I would like to learn more about safety and this is my question: why do not use neutral as a a ground wire? As far as I understand they are connected any way at a main panel. From theoretical point of view they have the same potential and if we disregard wire impedance they essentially are the same wire. I am sure that there is a reason to put so much extra copper in wiring, but what is the reason?

Thank you in advance,

Barmaley
The reason they do this is so we can use earth protection devices.
Electricity suppler in the UK use 2 core cable from the transformer into the building and you connect your fuse board upto the fused side, live and neutral, your earth connects into the neutral before the fuse board. so in the UK we do use the neutral as the earth wire. we call it TN-C-S Terra ( Earth) Neutral Combined Separated.
 

studiot

Joined Nov 9, 2007
4,998
so in the UK we do use the neutral as the earth wire. we call it TN-C-S Terra ( Earth) Neutral Combined Separated.
This is only part of the story.

TN-C-S (usually a PME system) is unusual and not the preferred TN-S system and is only available in special circumstances.

The TN-C system is also available for private generation facilities.

The letters have the following significance

The first letter (T) indicates that at least one point of the supply is connected directly to earth.

The second letter (N) indicates that exposed metalwork is connected to the supplier's earth.

The third letter (S) indicates the neutral and earth are totally separate systems, (C) indicates they are combined.

The -C-S indicates multiple cross connections between earth and neutral (hence PME = protective multiple earthing)

go well
 

Wendy

Joined Mar 24, 2008
21,914
No, you have this wrong. There is no circumstance where the ground wire should carry current, ever, in the USA or EU.
 

JMW

Joined Nov 21, 2011
122
A couple of points. GFI's operate by sensing the difference in current between the hot and neutral legs. If there is a difference in current, they open the hot lead. A difference indicates there is a current flow, hopefully through the 3rd wire, but maybe through the operator.
They do NOT need a ground lead to operate. Had this discussion with an snipe O3. (He bought dinner). As for grounds and neutrals, this discussion does not apply to PR, here we use the carrier as neutral. I have a metal pole on the property. A ground wire is welded to the pole but is broken at the ground rod, I was told this ground is not necessary as the house has a rod, the pole is buried and there is a guy wire. Even so it is a bit disheartening to see a black wire with with white tape, butt connected to the carrier.
We don't have copper wire thieves here, we use AL.

Regards,

Jim W
 
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