[Premium-Rx] Re: Lightning strikes

[George Georgevits]

John,

As I showed in my simple calculations, a single earth stake is virtually
useless against a direct strike, even in the most favourable soil
conditions. You have just provided direct experience showing this to be the
case.

Regards,
George Georgevits
Power and Digital Instruments Pty Ltd


-----Original Message-----
From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org]On Behalf Of J. Forster
Sent: Wednesday, 4 June 2003 3:02 PM
To: George Georgevits
Cc: Premium-RX LIST
Subject: [Premium-Rx] Re: Lightning strikes


  In the early 1960s I spent the summers in upstate New Your, on an island
in
the St. Lawrence River. The island was about 3 miles long and composed of a
large dune and some rock. The power and telephone lines ran along the ridge
that
formed the backbone down the center of the island. This is an area that has
some
pretty impressive thunderstorms.

Incident 1:  My dad and I were sitting in the boathouse, watching a
thunderstorm
through the open doors of the slips. In the corner of the boathouse was the
electrical service panels, with a large diameter wire going to a ground rod.
The
ground rod was several feet long and went into soil, sodden with water. The
land
was barely not a swamp and had been reclaimed behind a seawall.

Lightning apparently hit the wire along the island's ridge and a huge spark
jumped from the electrical service box to the ware in the boat slip, a
distance
of approximately 15 FEET. It was a nice, big, fat spark. I know because I
was
about 10 feet away from it.  So much for ground rods in wet soil.

Incident 2:  The next summer, the family were in the house, which was some
distance from the boathouse (300'). The power and telephone went underground
from the boathouse panel described above through an old, tar covered cable,
to
the house. One evening, another thunderstorm came by and another giant spark
jumped from a light switch on the wall to a ho air heating vent, below the
switch by about 4 feet.  So much for cable insulation being only good for
100s
of volts.

Moral:  Beware of lightning. There is no such thing as a good grounding
system.
If in doubt, make your ground bigger.

BTW, the (vacuum tube) electronics of the day survived both quite nicely.

-John




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