[TowerTalk] Fwd: Re: Re: lightening strike

[Jim Lux]

On 7/12/13 5:51 AM, Bill Weinel wrote:
> On Thursday, July 11, 2013 07:31:59 AM Jim Lux wrote:

>> The bonding wire needs to be big enough to carry the maximum expected
>> fault current without melting.  The worst case for this is not
>> lightning, but a local medium voltage power line shorting to your
>> wiring, because it could source several hundred amps for seconds, before
>> something trips.  Lightning has really high peak currents, but the pulse
>> only lasts 50 milliseconds, so there's not much energy dissipated in the
>> grounding conductor. (AWG 10 is big enough to handle all but the largest
>> lightning strokes without melting)
>
> True. That's why I prefer larger conductors for the 'just in case' scenarios.
> Thanks for the corrections and observations Jim.
>


And I find that I made a mistake too.. the lightning pulse is typically 
about 50 micro seconds long, not 50 milliseconds.  1-2 microsecond rise 
time from 10% to 90% and then a fall time  50 milliseconds to 50% is a 
standard test waveform.