Live earth neutral and the cut out fuse

[dokkan1080]

Learning and curious

At my home the neutral and earth are joined by the cut out fuse.

The neutral goes up to the meter and the earth goes straight to the board.

I can't wrap my head around how the earth and neutral are different?

When the cut out fuse is out ( some one broke the seal along time ago shhhh)

I have continuity on the incoming side of the switch between live and neutral and between the live and earth. And between the neutral and earth.

Is this because the live and neutral are joined in the meter? And because the neutral is also joined with the earth at the cut out fuse?

Its driving me mad

 

[buzzlightyear]

have continuity on the incoming side of the switch between live and neutral and between the live and earth. And between the neutral and earth.

There are combined known has TNCS
to others PME.

 

[buzzlightyear]

https://www.google.com/url?sa=t&sou...FjAWegQIRBAB&usg=AOvVaw3HgSKmtciFGMrVS4CUAK-H

 

[dokkan1080]

There are combined known has TNCS
to others PME.

And that gives continuity across everything :/?

Its hard to visualise it?

 

[buzzlightyear]

Its hard to visualise it?

https://www.google.com/url?sa=t&source=web&rct=j&url=https://professional-electrician.com/technical/protective-multiple-earthings-pme/&ved=2ahUKEwimw5Su1q3uAhWDRxUIHTV4CywQFjAMegQIAhAB&usg=AOvVaw3lf0mWZGbr5kMzr16p0e7M

 

[Lucien Nunes]

Earth and neutral are solidly connected together at the DNO's transformer. In TN-S you will read that as continuity via the distribution cables, but there will be a superimposed voltage due to the current flowing in the neutral from other installations, that may disrupt the meter. With TN-C-S regardless of what other connections exist, there is one in your own service terminal (head) so you will easily read sub 0.1Ω N-E and there won't be any potential difference.

There will also be some kind of a circuit L-N through the meter, as it requires power both in order to function and to measure the line voltage. Exactly how that will show up on a continuity test will depend on the exact circuitry inside that particular model of meter. A traditional induction meter with a rotating disc, you will read the resistance of the voltage coil between L-N. An electronic meter could have a number of different internal power-supply circuits that would give you different readings.

 

[dokkan1080]

Earth and neutral are solidly connected together at the DNO's transformer. In TN-S you will read that as continuity via the distribution cables, but there will be a superimposed voltage due to the current flowing in the neutral from other installations, that may disrupt the meter. With TN-C-S regardless of what other connections exist, there is one in your own service terminal (head) so you will easily read sub 0.1Ω N-E and there won't be any potential difference.

There will also be some kind of a circuit L-N through the meter, as it requires power both in order to function and to measure the line voltage. Exactly how that will show up on a continuity test will depend on the exact circuitry inside that particular model of meter. A traditional induction meter with a rotating disc, you will read the resistance of the voltage coil between L-N. An electronic meter could have a number of different internal power-supply circuits that would give you different readings.

So earth and neutral are the same they just go into different bars in this case...

The neutral is the return path so why does the circuit breaker operate when the earth is turned into the return path in the case of a fault....if they are the same

 

[pc1966]

I can't wrap my head around how the earth and neutral are different?

They are both nominally at 0V, and as Lucian pointed out in another post what makes the neutral neutral really is the fact that somewhere it is earthed.

The reason they are separated within most systems, and certainly within any installation in the UK complying with current regulations, is that the neutral is "live" in the sense it carries current during normal operations. So strictly speaking the L is "line" as the one at a high voltage relative to earth, but both L & N are "live" as they carry power normally.

So if you have the neutral go open due to a fault, one end goes to the supply voltage. If that is also used to earth exposed metalwork, then that metalwork becomes dangerous!

That is a real risk with the TN-C-S system you have (TN-C means combined N & E, TN-S means separate N & E) is a fault on the combined N & E section (known as CNE, PME, or PEN) makes the earthed metalwork in a house live. All of it.

In the house that is no real risk if it is bonded to extraneous parts like gas and water pipes, as all are at similar potential so you don't touch a dangerous difference inside. But outside it is a different matter and every year there are a few incidents reported to HSE due to this. The risk being greatest for some special cases like hot-tubs or electric cars where people might be wet and in contact with the true Earth as well as the metalwork.

 

[James]

A direct live to N connection will give a slightly bigger bang than a live to E connection.

Due to the N cable being. Thicker

 

[Lucien Nunes]

MCBs are in the line. They will trip just the same whether a fault is to neutral or to earth, they can't tell the difference. RCDs monitor the line and neutral, and trip if there is a difference in the current between them. Although neutral and earth are the same conductor as far as the service terminals, they are separate conductors by the time they reach the consumer unit and RCD. Therefore the RCD can sense whether some of the line current is not returning to the service terminals along the neutral (which must then logically be going to earth, either the CPC or the mass of earth)

 

[pc1966]

The neutral is the return path so why does the circuit breaker operate when the earth is turned into the return path in the case of a fault....if they are the same

The RCD look at the difference between the L and N on the load side. A return current (leakage, shock from touching live, etc) back to the N at the supply side, or to true Earth, will cause an imbalance and trip the RCD.

 

[pc1966]

Drat, just beaten by Lucian! again!

 

[buzzlightyear]

Drat, just beaten by Lucian! again!

you need to be quick in this game ,maybe you got big fingers like a giant .lol.

 

[Lucien Nunes]

We're all too helpful, fighting to save the world from imminent collapse due to electrical misunderstanding