Stefek Zaba wrote:

(not sure what significance the supply being TT would have on PSC mind
you)

A terminogical inexactitude, to a degree. The earthing derangements will
make naff-all difference to the PSC for an L-N fault, but will clearly
affect the current which'll flow for an L-to-E (or, since the
distinction is crucial here, actually an L-to-protective-conductor)

I guess I was kind of hinting (gently) that the term PSC implies a L-N
short, rather than L-E.

Hence the fact that it is TT (from an earthing arrangement point of
view) will make no difference, although to be fair the likelihood of a
TT setup being out "in the sticks" a long way from a substation is
greater, and hence _may_ have a higher supply impedance as well.

fault. It's precisely becuase the impedance of a local earth rod can't
be expected to be low enough to get a hefty enough fault current to flow
that UK regs [note trimming of followups :-] require a 100mA RCD on all
TT installs.

As you know anyway ;-)

;-) (yes painfully... having just spent a fortune on a big pile of CUs
and RCDs ready for the great CU replacement party....)



--
Cheers,

John.

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