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Re: Grim Safety Reminder
Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>
Tesla list wrote:
> Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> I have seen, off 11kvac (RR Catenary,) sustained arcs to
> 3 feet or so. Pans were faulty, would rise, then drop, pulling the
> arc out. My Aunt & Uncle were hiking a power line, saw an arc
> to pine tree. Being Good Doobies, they noted the pole number,
> called it in. Power Co said 'thanks. Good to know where. We've
> been hunting that one but could not find it. Too intermittent.
> Common cause is 'switching surge', which can put a megavolt spike
> on a 200kv line: these travel until dissipated, OR they find a
> point to spark over. Or lightning can do the same.
> Tesla list wrote:
> > Original poster: "John H. Couture by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
> > The cable installer may not have been "very stupid". He may have been a
> > victim of the stupidity of safety engineers that do not understand the
> > spark". Sparks from distribution lines can be several meters long. Refer to
> > "The Long Spark" page 231 of "Lighting", Volume 1, edited by R.H.Golde,
> > Academic Press, 1977.
> > I have read of several of these accidents and investigated a couple of
> > electrocutions. The long spark is created under special conditions that are
> > not well understood. People can be several meters from the power lines and
> > still get zapped.
I've been following this with interest and respect, as I once saw the
results of a horrible accident myself. I also have seen very long arcs
following an accidental short, but hadn't leard of the "long spark"
matter before. That's interesting, but seems to go counter to something
I've seen. When I was going to Caltech in the late 40's we took a field
trip to some of the SCE high sierras hydro plants. At the first of
those, built in 1913 as I remember, there's a 220 kV line going out
toward LA. The output conductors go out through an open window, and the
clearance is much less than 10 feet. The operator showed us a stunt
which he obviously did to impress all visitors. He took a "hot stick"
which wasn't more than 6 feet long and used the conductive hook end to
draw arcs from the HV! His hand wasn't more than 6 feet from the hook,
and the wood must have been somewhat damp as the stick was sitting in
the open room, with some spray from the turbine outflow. Point is, that
if guys were still pulling this stunt after over 30 years I would think
someone would have been fried along the way and the demos would have
ended abruptly. ?????????