In alt.engineering.electrical Andrew Gabriel wrote:

| Yes, although we have 3 types of supply arrangement for earthing
| used on public supplies. (Note that on 240V, there's often far
| more distance between the consumer and the transformer than
| you'll find in the US on 120V supplies.)

Our supplies to homes are also 240V. We just ground it in a different
way through the use of a center tap and an additional wire, which gets
the neutral designation. For an equivalent _balanced_ load in the US,
we should see no more voltage drop than in the UK. And that voltage
drop will be effectively halved between one of the hots and the neutral.


| TN-S:
| Neutral is grounded only at the transformer, but a separate
| earth conductor is carried in the supply network and brought
| into the home from that same grounding point.
|
| TN-C-S (also known as Protective Multiple Earthing):
| A single PEN (Protective Earth and Neutral) conductor from
| the transformer serves as both neutral and ground connection
| in the supply network. The PEN conductor must also be earthed
| regularly throughout the supply network, and it requires very
| high integrity connections to ensure the risk of it breaking
| is very low (this is a legal requirement). Once the supply
| reaches the consumer, the PEN conductor is split into separate
| neutral and earth conductors in the installation.
|
| TT:
| The supplier grounds the neutral as for TN-S, but doesn't
| provide the consumer with any earthing connection. The
| consumer needs to make their own ground connection for earthing
| (and shouldn't cross-connect this to the neutral).
| TT is only found on old rural overhead supply networks, and
| they are upgraded to TN-C-S when due for refurbishment.
|
| Even if the supplier does provide an earth connection (TN-S
| or TN-C-S), the installation can choose to ignore it and be
| wired as a TT system. This is sometimes done for submains
| to outbuildings and outdoor electrics, even when the main
| installation is TN-S or TN-C-S.
|
| These earthing system arrangements are covered in the uk.d-i-y
| FAQ: http://www.diyfaq.org.uk/electrical/...al.html#system

Nice info!

I'm curious about this: is it legal in the UK for a home to feed their supply
into their own transformer and ground the secondary at that point as a new
system?

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