TT system - Reg 411.5.1

[davesparks]

How would TN-S work if there’s no reference to earth?

If there is no reference to earth, and it is intentionally designed to be this way then it would be IT, It won't be TT.
If there is no reference to earth when they is supposed to be then it will be dangerous.

 

[Deleted member 26818]

If there is no reference to earth, and it is intentionally designed to be this way then it would be IT, It won't be TT.
If there is no reference to earth when they is supposed to be then it will be dangerous.

Yes, which is why they are saying, reference one of the line conductors to earth.

 

[Bobster]

How would TN-S work if there’s no reference to earth?

It's not TT due to the fact that the reference point isn't transferred through the mass of earth. I.e from a rod at a house to the DNO tx.

A generator with a Rod is TN-S as in all intents and purpose it can be treated as a transformer secondary. Albeit with a low potential earth fault current.

You wouldn't rod a genny and then run phases to whatever you were feeding without a CPC just to install a second rod there. (This instance it would be TT)

 

[stevethesparks]

Sorry to resurrect this thread but has the original question ever been answered elsewhere?

 

[UKPN]

Just looking at the second part of this reg with the statement " The neutral point or the midpoint of the power supply system shall be earthed. If the neutral point or midpoint is not available or not accessible, a line conductor shall be earthed"
My question is... I assume they are talking about the connection at the transformer sub station and if so why did they feel the need to add this, as I haven't seen it there before now?

Its all part of the wiring regs poking their nose into DNO matters. Just disregard it.

 

[Julie.]

Its all part of the wiring regs poking their nose into DNO matters. Just disregard it.

Not really.

Many end users have their own transformers taking in at a mv or hv supply

To them, the earthing arrangements are very much to do with them, and not the DNO.