On 18/05/2011 22:21, jgharston wrote:

Just had a quick look at my (20-year-old) lecture notes,

Two changes of regs since then; time to ditch the old notes I reckon.

Obstacles and placing out of reach are shock protective measures against
direct contact (now known as basic protection) only. They're not
relevant to indirect contact (now called fault protection), so are
something of a red herring in this thread.

And yes, as Owain has said, they're now applicable only to supervised
installations (skilled or instructed persons), which rules them out for
normal domestic installations. [See section 417 in the 17th ed.]

To answer The Scullster's original question: shock by indirect contact
means contact with parts which are live as the result of a fault.
Automatic Disconnection of Supply was traditionally provided by the
blowing of a fuse (or fuses), later by MCBs or alternatively by ELCBs
and RCDs where Zs is too high to assure operation of an OPD.

--
Andy