[TenTec] Another grounding thought and personal observation

[Bill Fuqua]

At 01:11 PM 8/12/2003 -0500, you wrote:
>Let me get this straight.    Charge starts to build, from the earth (you can
>hear the frying in the guys and tower)  unless there is some way to
>dissipate the static build up (corona balls, large dissipation brush, etc)
>this charge will continue to build until the charge energy is at such a
>large level that the air gap between the earth and clouds arcs over.


Talk about "snake oil" this dissipation brush thing is nuts. A bunch of 
sharp wires on the top of an tower is supposed to prevent lightning? If 
there is a high potential between these wires and the clouds it will cause 
field ionization of the atoms and molecules at the sharp tips of the wire. 
This will not dissipate the charge ( lots of coulombs stored between earth 
and clouds) at all unless
there is a tremendous discharge ( lightning).
         Where the lightning goes depends where the random paths of the 
cosmic rays that strike the atmosphere. The cosmic rays ( very high energy 
particles) leave ionization trails that cross each other and when these 
paths happen to make a connection between the clouds and earth there is a 
discharge. That is why lightning seems to be a bunch of connected straight 
lines.
         The guys that sell the dissipation brushes put these on top of a 
little Van de Graaff generators and then show that they get a much smaller 
arc off the dome than without the "brush". However, the charge on the dome 
of the Van de Graaff is very small and the rate at which it can be charged 
(current) is limited by the amount of charge the little rubber belt can 
carry from the grounded base to the dome.  The field ionization at the tips 
of the wires produces a corona that discharges the dome of the Van de 
Graaff and in effect reduces its voltage.  We use corona loading to 
regulate the dome (high voltage terminal) voltage on our large Van de 
Graaff accelerator. And when it discharges at 5 or 6 MV it makes quite a 
noise. Lightning involves many more coulombs of charge than the salesman 
would have you think.


73
Bill wa4lav