On 1/13/12 5:39 AM, Stan Labinsky Jr. wrote:
> John, your understanding that short is better is correct, however, taking a
> path right through your house is not, never, ever!
> Consider also that the outside path, if accomplished with bare wire will
> create a more intimate connection to earth which is what you want. I'd
> suggest that at the corners of the run, that you drive ground rods.
> Lightning doesn't like sharp bends, but having the rods at those points will
> augment the strike energy's access to ground.
I don't know if there's any truth to the "lightning doesn't like sharp
bends"... I'd like to see some physics behind that.
90 degree bends don't have much inductance over the length of the wire
(that is, measure the inductance of a meter of wire in a straight line,
and then measure it after being bent in a 90 degree arc, or a sharp
angle, and it will be the same).
There are mechanical reasons why bends are bad: the electromagnetic
forces tend to pull the turn apart.
Something to think about, length wise... Either route is "long" in terms
of the inductance (i.e. it's many microhenries). Either route will
have many kilovolts of drop with a typical lightning rise time of 1-2
V = L di/dt... If the full 20kA stroke is the i, you're looking at di/dt
of 20E9 Amps/sec... 20kV per microhenry.
As Jim pointed out.. the whole goal is to get everything that is
physically close to move together, so you don't get large "box to box"
currents (or arcs). It's inevitable that one side of the house is going
to be different than the other.
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