Hi all,
let me bring a different perspective. In the aircraft world we have a
lightning tests that stress interface wiring travelling some distance WRT
local wiring.
The reason we do this is because when lighting strikes the plane, the
fuselarge(?) carries MANY amps, and there is a voltage drop between any two
points. If a piece of equipment is connected to a another some distance away,
the interface lines can see many hundreds, even thousands of volts.... Even
the capacitive coupling between the equipment case and the surroundings is
enough to see this effect.
If this situation is on the ground, and lightnig strikes a part of the
building that causes PE current to flow in the buiding ground. The wires
connecting to other equipment will ride the shift in ground potential. the
greater the distance, the larger the shift. It does not have to be in a
seperate building.....
Since only data/com lines travel some distances, thay are most likely to
encounter this threat. I suspect that this is where the requirement comes
from. Now as for what levels to apply....
Have a great weekend,
Derek Walton
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