On 08 Apr 2008 21:04:35 GMT someone who may be Matthew Geier
wrote this:-

You don't drop a shorting bar across a live supply. The effect would be
some what spectacular and will probably throw molten metal around,
possibly causing nasty injuries.

An occasional poster to uk.railway has written of the time he spent
testing the various designs of such bars on live railway supplies
(as they have been used since the earliest days). IIRC one of the
parts of these tests was to see how the designs minimised the
chances of injuries.

While ideally they should be used just to ensure that supplies
cannot be re-energised I think that in an emergency they are still
used first. When radio communications become rapid, as they are in
some places, this may be changed/has been changed relatively
recently as it will then be at least as rapid to make a radio call
compared to getting hold of the bar, clambering out of the cab and
applying the bar.

People have been injured in the power industry by closing earthing
switches onto a live supply and then being splattered with molten metal
when the earth switch vaporised. (As they are not designed to switch live
and take the full fault current across their closing contacts)

Short-circuiting bars are not the same as earthing switches.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54