Pardon me, but this is the biggest collection of garbage on this subject
that I have seen. The braided copper conductors I have seen in explosives
storage were about 1/2 inch in diameter, and were braided to allow limited
flexing on installation. The individual wires were at least #12, and more
likely (from appearance) #10. Also, Army Ordnance, at least, thought they
were there for lightning grounding and dissipation, not just to calm the
fears of the peasants. Next time, get some facts before expounding .
At 11:17 AM 7/19/2006 -0700, you wrote:
> The first problem with braid is that the stuff forms a coating of
> copper oxide around each strand that is nonconductive. This coating makes
> each wire like a individual conductor with a resistance according to its
> gage. Now think of the flexing due to vibration, heat cycling, or any
> other thing which will cause the strands to rub against each other thus
> breaking the copper oxide surface. The crossover points of the braid will
> be alternatively be conducting and then reoxidizing to nonconducting
> state. This makes all the strands at different resistances which when the
> 20,000 to 200,000 amp surge hits them will cause some of them to take
> more of the current than others and vaporize. An avalanche effect occurs
> and you have meltdown and arcs.
> Second we have the idea that all the current will travel on surface
> with the skin effect. This is true for normal current amounts but at the
> current levels of lightning there are not enough free electrons at
> accommodate the current flow and the conductor depth comes into account.
> If not enough depth is available the current has to flow outside of the
> conductor in a arc as there is no where for all those electrons to go.
> The use of braided strapping to protect ammunition was to prevent a
> static discharge from detonating the charges not the high current of
> lightning. In the workers minds they thought it was for lightning but all
> you can do with lightning is shunt the current, not stop flow. Even if
> you shunt 99% of current there is enough voltage to arc at even micro
> amps which is enough to make fireworks out of your munitions. The only
> safe place was inside of conductive box with lid closed. (i.e. ammo
> boxes, metal lined bunkers, etc.)
> That leaves us with either large stranded (each strand #12 or
> larger) or solid conductors. Even solid has enough flex to allow a
> fold-over to work if you disconnect(or never use ) the ground opposite
> the hinge.
> Save your braid for your indoor station ground applications.
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Bill Aycock - W4BSG
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