On 10/03/2011 06:46 PM, Brian Lawson wrote:

And for Iggy...I've seen 120 volt hanging cables that were in very
damp conitions shorted, and they arc and catch fire and burn like a
dynamite fuse or like a July 4th hand-held "sparkler"...they don't
blow a fuse for about 5 feet.
We had the 4160 feed straight from the utility transformer (a couple
MVA size) short in underground cables. To balance return currents on
the conduit, they run every phase and neutral in each parallel conduit,
in this case 4 conduits in parallel. One of them developed a fault
underground. The chief electrician heard a nasty buzzing coming from
the switchgear room and stuck his head in, and saw blinding blue light
and concrete chunks flying around, and quickly beat a retreat. They
needed the utility to send a truck out to shut off the transformer, they
couldn't do that remotely without blacking out the whole region.

It trenched about 40 feet of concrete and was heading toward the
transformer when the utility got the transformer shut off.

Jon