Owen Duffy wrote:
"Rick (W-A-one-R-K-T)" wrote in
news

On Sun, 15 Jul 2007 17:23:13 +0000, Walter Maxwell wrote:


This topic has aroused my curiosity. As a grounding device, why would a
solid rod be better than a hollow pipe, except for the current carrying
capability?

Good afternoon, Walt.

The thing is, the current carrying capability for transient events like
lightning strikes should be about the same for the same diameter pipe or
rod, since most of the current is carried in skin effect anyway.


I think that is flawed thinking.

A lighning down conductor needs to carry something like 20kA for 100ms, so
it needs to be substantial enough that it doesn't melt and remains in place
to protect against the next strike.

Owen

The fusing/melting current for 1/2" copper pipe is probably well above
20kA, even for 100ms pulses. A more interesting potential failure mode
might be from the mechanical forces due to the magnetic field. (see,
e.g., quarter shrinking or can-crushing)