Gene,
does anyone run simulations or calculations on lightning strikes. A common
direct stike is 100 kA with a risetime of 8 us, correct? If so, using an
inductance of 200 nH/ft, the voltage drop along 1 foot of wire is 2.5 kV. And
we can
calculate the low frequency impedance of a ground system. Let's say it is 1
ohm. Now we have 100 kV between the tower base and earth ground.
Using some ball park numbers like this we should be able to determine the
currents and potentials at various points in the system. Then appropriate
series
Z and shunt Z can be applied to design for survival of equipment.
I'm thinking of doing it via design rather than blindly by code. I suppose
that there is nearly 100 years of experience contained in the codes that will
lead one to success. But perhaps a good understanding of the nuances can help
one to gain several dB of margin by some simple additions.
Can someone steer me to some numbers on lightning? Thanks.
Dave WX7G
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|