On 2/2/15 10:15 AM, Mike Fahmie via TowerTalk wrote:
Fortunately, wiring used in lightning protection does not have to carry
sustained current so the thermal mass of the wire can be used as a thermal time
constant to increase its carrying capacity.
Using "Lightning and Lightning Protection", 1979 as my reference, the impulse
carrying capacity of #6AWG copper wire is 200 KA for 300 microseconds, fusing at 300 KA
in the same time. The same text states that 99% of strikes are less than 60,000 amperes
and with shorter durations.The Codes may require heavier wire, but it seems that 4 or 6
AWG is sufficient for most eventualities.
-Mike-
you can look up the Preece or Onderdonk equations too..
Large diameter wire is required for mechanical reasons: it won't get
broken accidentally, or it's strong enough to resist physical damage
from electromagnetic forces.
a 10 turn coil of AWG10 about an inch in diameter explodes with a fast
10kA pulse (see "quarter shrinker")
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