> I've seen accounts of an extremely  substantial arc being drawn between
> telephone exchange busbars fed from 50V N,000 Ah lead acid batteries -
> probably 2000-3000 Ah.
> In one case technicians had unbolted locating clamps while the busbars we=
re
> carrying telephone exchange current - probably hundreds of amp, and did
> not realise that there were strong attractive forces present. Oops. The c=
ircuit
> was eith unfused or the fuses were happy to sustain the arc and it had to=
 be
> extinguished by 'other means'.
>=20
> In another incident someone shorted between two busbars with a metal
> vacuum cleaner suction tube. !

That would be impressive.

The other story I have heard along similar lines was from a guy who had als=
o been in the telephone exchange area of work, and they would get the appre=
ntice to unto the battery terminals. Invariably this involved a spanner of =
length long enough to span the two terminals on a battery, and the operator=
 was supposed to put a suitable insulating barrier over the other terminal.=
 Almost invariably the apprentice didn't, and on graduation they would be p=
resented with the terminal clamps from the cable with the ends of the spann=
er welded to them. The middle section of the spanner was long lost in molte=
n globules on the floor...



--=20
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