Sammo wrote:

I am the original poster with two 30m extension cables. You refer to
RCD protection.

I have got a plug-in RCD device but I know nothing about earth fault
loops. It is similar to the one in this illustration.
http://www.argos.co.uk/wcsstore/argo...IFN104773M.JPG

See my reply elsewhere in this thread for a fuller description of earth
fault loop impedance. Also see here for more background:

http://www.tlc-direct.co.uk/Book/5.1.1.htm

Where should my RCD device be plugged in to best avoid the problem of
earth fault loops:

(1) At the mains supply end where the first extension goes into the
mains socket.

Yes

(2) In the middle of the two 30m extensions.

No - but better than 3

(3) At the far end of the two extensions where the appliciance I am
using is plugged in?

no - but better than not at all!


Having the RCD at the start of the cable will mean the whole cable is
protected by it. So should you accidentally do the "hedge trimmer
through the extension lead" exercise, the RCD hopefully will cut off
power to the lead, rather than leaving live exposed conductors flopping
about in the wet grass under your ladder!



--
Cheers,

John.

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