"Neutral" as a correct term

[Gardner]

Is neutral the correct word to use on a 2 wire TN-C-S supply coming from a single 11kv-240 volt single phase 2 terminal secondary transformer? Or would it technically be called the earthed conductor instead?

 

[davesparks]

What is the number of the section?

Somewhere in the first few pages you'll find a section called definitions

 

[Leesparkykent]

What is the number of the section?

part 2 definitions, page 32 BYB

Edit: Ruston beat me to it :smile5:

 

[ruston]

part 2 definitions, page 32 BYB

Lol.:smile5:

 

[Gardner]

part 2 definitions, page 32 BYB

Edit: Ruston beat me to it :smile5:

Has me a bit more confused:

 

[Sisyphus]

Gentlemen,

If i may , this is what the '14 NEC has>

Neutral Conductor. The conductor connected to the neu-
tral point of a system that is intended to carry current under
normal conditions.

Neutral Point. The common point on a wye-connection in a
polyphase system or midpoint on a single-phase, 3-wire sys-
tem, or midpoint of a single-phase portion of a 3-phase delta
system, or a midpoint of a 3-wire, direct-current system.

Informational Note: At the neutral point of the system, the
vectorial sum of the nominal voltages from all other phases
within the system that utilize the neutral, with respect to the
neutral point, is zero potential.

~S~

 

[Gardner]

Gentlemen,

If i may , this is what the '14 NEC has>



~S~

So under NEC terminology, neutral is defined as a conductor which only has a phase cancellation relationship with two or more actives?

 

[davesparks]

So under NEC terminology, neutral is defined as a conductor which only has a phase cancellation relationship with two or more actives?

That's a question for an NEC forum really, we don't deal in those matters here.

 

[Gardner]

That's a question for an NEC forum really, we don't deal in those matters here.

But Id imagine Sisyphus does, which is why I asked. And I think you knew that...

 

[Richard Burns]

You have jumped in the definitions that Sisyphus posted from neutral conductor to neutral point.
In either case of BS7671 or 14 NEC the neutral conductor is one that has a (near) zero potential and is intended to carry current, as Lucien said in post 5.

In terms of your example if it is a TNCS supply then the neutral from the transformer would also be the earth conductor so the conductor would be a protective earth neutral conductor or PEN conductor.

 

[Besoeker]

This thread has veered off course and no longer neutral lol

As others have said, in context, it is defined as neutral by the regs. It has no potential and therefore neutral.

It has a potential difference to what is called live. Otherwise you wouldn't have any transfer of energy from source to load.
And you couldn't make your morning cuppa...........

 

[Gardner]

You have jumped in the definitions that Sisyphus posted from neutral conductor to neutral point.

I think he was just trying to help. I welcome any knowledge or new way of looking at something. He posted neutral point because by the looks of it in order for a conductor to be called a neutral under the NEC it must have a symmetrical phase angle relative to two or more live conductors. In order for uch to take place, it must originate from a central neutral point at the source.

In either case of BS7671 or 14 NEC the neutral conductor is one that has a (near) zero potential and is intended to carry current, as Lucien said in post 5.

From the definition in BS7671, the secondary of a two wire earthed AC supply should not be called a neutral conductor. A 2 wire DC yes, but not AC.

In terms of your example if it is a TNCS supply then the neutral from the transformer would also be the earth conductor so the conductor would be a protective earth neutral conductor or PEN conductor.

Correct, but in neither (TN-S or PME) case should it be called a neutral when referring to the regs.

 

[Richard Burns]

I think he was just trying to help. I welcome any knowledge or new way of looking at something. He posted neutral point because by the looks of it in order for a conductor to be called a neutral under the NEC it must have a symmetrical phase angle relative to two or more live conductors. In order for such to take place, it must originate from a central neutral point at the source.

You could well be correct here for the NEC, from the definition posted.
BS7671 mentions a neutral point but does not define a neutral point (clear as mud)

From the definition in BS7671, the secondary of a two wire earthed AC supply should not be called a neutral conductor. A 2 wire DC yes, but not AC.

If you look at chapter 31 in BS7671 this shows various arrangements for supplies and identifies the neutral conductor (if there is one) in these cases.
I am afraid I am not sure what you mean by the secondary of a 2 wire earthed ac supply.
A two wire earthed ac supply would be earthed on one side and this side would be a neutral conductor, the other side of the supply being the line conductor.

Correct, but in neither (TN-S or PME) case should it be called a neutral when referring to the regs.

In a TNS arrangement the conductor running from the earthed centre point of a supply to the incomer of an installation and intended to carry current would be a neutral conductor as it is not earthed along its length.

 

[Gardner]

You could well be correct here for the NEC, from the definition posted.
BS7671 mentions a neutral point but does not define a neutral point (clear as mud)

Correct, hence why I am being thrown off. Is neutral point the earthed point or the point which has current cancellation?

The NEC calls earthed conductors grounded conductors, reserving neutral for current cancellation.

If you look at chapter 31 in BS7671 this shows various arrangements for supplies and identifies the neutral conductor (if there is one) in these cases.
I am afraid I am not sure what you mean by the secondary of a 2 wire earthed ac supply.
A two wire earthed ac supply would be earthed on one side and this side would be a neutral conductor, the other side of the supply being the line conductor.

Under the definition of BS7671 it would not be a neutral conductor for an AC circuit. "...or the earthed conductor of a two wire DC circuit" Nowhere is AC mentioned when in regard to 2 wires on being earthed.

Let me check chapter 31.

In a TNS arrangement the conductor running from the earthed centre point of a supply to the incomer of an installation and intended to carry current would be a neutral conductor as it is not earthed along its length.

But if the 3 wire supply is single phase rather then 3 phase, is that point still neutral? It might not be for AC.

 

[shanky887614]

the return path is the neutral.

we get 230v between any live and n/e.

but nothing from n-e

on three phase we get 400v between any two/three phases/lives/hot


a three wire supply can mean one of two things.

scenario a

1. line
2. neutral
3. earth

scenario b

1. line 1
2. line 2
3. line 3

in scenario b its called three wire as that is all that is provided by the utilities company and the client must supply there own earth

 

[davesparks]

But if the 3 wire supply is single phase rather then 3 phase, is that point still neutral? It might not be for AC.

In our nomenclature you don't have a 3 wire single phase supply, single phase will always be 2 wire (we only count the live conductors)
A 3 wire supply could be 3phase or 2 phase (or bi-phase/ split phase)

 

[davesparks]

the return path is the neutral.

we get 230v between any live and n/e.

but nothing from n-e

on three phase we get 400v between any two/three phases/lives/hot


a three wire supply can mean one of two things.

scenario a

1. line
2. neutral
3. earth

scenario b

1. line 1
2. line 2
3. line 3

in scenario b its called three wire as that is all that is provided by the utilities company and the client must supply there own earth

Neutral is only the return path in single phase, and partially in a three phase + neutral supply.

A 3 wire supply is either 2 phase (bi-phase/split phase) or three phase, you only count the live conductors.