Stefek Zaba wrote:

Andy - aren't the b*ggers - however sliced-n-diced-n-microprivatised -
still under a legal obligation to tell you what your earthing
arrangements are, and what the maximum supplier's earth loop impedance
is (even if the latter will almost always be the Conventional answer of
'0.35/0.8/yourproblem' respectively for TN-C-S, TN-S, and TT ;-) ?

Yes, there's a list of data they are obliged to provide in the BS 7671
Amendment 2 which I've just mentioned in another thread. Here's a quick
cut'n'paste. I've added the usual answers (for LV supplies) and some
comments in square brackets:

quote
Regulation 28 of the Electricity Safety, Quality and Continuity
Regulations 2002 requires distributors to provide the following
information to relevant persons free of charge:

- The maximum prospective short-circuit current at the supply terminals
[1-ph: 16 kA; 3-ph 25 kA; can be higher in the former LEB area]

- The maximum earth loop impedance of the earth fault path outside the
installation (Ze)
[TN-S: 0.8 ohm; TN-C-S: 0.35 ohm, TT: 21 ohm]

- The type and rating of the distributor’s protective device or devices
nearest to the supply terminals
[usually BS 1361 Type 2, 100A, or whatever records show for older stuff]

- The type of earthing system applicable to the connection
[TN-S, TN-C-S or TT, but their records may be inaccurate - consumers can
to some extent change the means of earthing without reference to the
distributor]

- The number of phases of the supply
[this tends to be either 1 or 3 ;-)]

- The frequency of the supply and the extent of the permitted variations
[50 Hz ±1%]

- The voltage of the supply and the extent of the permitted variations.
[230/400 V -6%/+10%; -10% after 2008, perhaps]
/quote

--
Andy