I agree there is little chance of a lightning flash from a guy line or
other part of the tower installation as long as the ground systems of
all components are tied together and all are adequate to limit the
voltage to less than the thousands of Volts required for a spark or
flash between components. Voltage difference between the tank and guy
or other conductor is the key variable that determines whether or not a
flash may occur. Preventing a flash is much easier than protecting the
rig gear from damage.
In the case of the guys, that high voltage might develop if the
turnbuckles, eyes, and other points of small area contact are not
bypassed by a proper ground wire. In any case, protecting the rig
components, which are sensitive to much less overvoltage than might
cause a flashover, requires grounding the guys at a point above
turnbuckles, etc and above the snow line (to prevent corrosion). That
ground should be tied back to the rest of the tower ground. PolyPhaser
offers advice regarding this.
The copper gas line, underground, probably is a good ground. But, it
probably connects to the tank through a regulator, and I don't know if
that is a good idea.
Now, I need to examine the propane tank here and see how or if it is
grounded and whether it is inside the protected volume of a nearby dipole.
By the way, a recent book on lightning, _Lightning: Physics and
Effects_, Dr. Vladimir A. Rakov and Dr. Martin A. Uman, 2003, Cambridge
University Press, offers updated information about the protected
volume. For structures under 20 meters high, a 45 degree cone offers
about 90% protection against direct strike; a 23 degree cone offers
about 99% protection. The rolling sphere concept is a better way to
determine protected volume around taller structures.
73 de WOØW
Keith Dutson wrote:
>I have a similar situation here where the guys run close to the propane tank
>and the anchor is about 30 feet from the tank. No problem has been
>encountered since installation in 1998.
>Actually I do not think there is significant danger with a propane tank and
>lightning since the copper service line runs straight to ground from the
>73, Keith NM5G
>[mailto:firstname.lastname@example.org] On Behalf Of Rick Bullon
>Sent: Saturday, April 29, 2006 9:35 PM
>Subject: [TowerTalk] OT: Propane Tank near lightning ground
>I am building a new house here, the house is close to the tower and the
>propane tank will be real close to the ground rods.
> Do I need to worry about the tank exploding if I get a lightning strike to
>the tower? The tank will be on a couple of large concrete flat blocks and
>not in contact will the ground.
>I feel the is a stupid question but I have to ask just so I can sleep in the
>new house at night
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