[TowerTalk] Does prevailing grounding scheme promote large ground loop?

[Jim Brown]

On Mon,7/25/2016 5:51 AM, jimlux wrote:
> What you want is everything that is "near" each other connected with 
> good conductors that are similar in length (so the inductance is 
> similar, and the voltage rise from the pulse is similar).
>
> If you have one piece of gear with a 10 foot cable to the lightning 
> impulse. And another piece of gear on the bench connected with a 100 
> foot cable to the lightning impulse, and then you interconnect the two 
> with a short jumper, you can see that there might be a problem.


The problem with this (and any) analysis of a lightning event is that it 
is FAR more complicated than anything we can compute, simply because the 
voltages and currents induced in any system (stuff wired together) will 
be different in each conductor depending on WHERE the strike is, the 
physical geometry of the conductors that make up that system, how energy 
from the strike gets to the earth, etc.

Remember that in any given lightning event, voltages/currents are likely 
to couple into our system (our home) via the power system, via the CATV 
system, via the telephone system, via our antennas, and directly onto 
all the wiring within our home. Voltages/currents will be very different 
between those multiple systems by virtue of THEIR geometry, how they are 
earthed and bonded, and THEIR proximity to the strike.

73, Jim K9YC