Re: Lightning protection

w_tom wrote:
>
>
> That is also true of lightning. Lightning is not some DC
> pulse. Lightning is AC electricity - at numerous radio
> frequencies.

Isn't the definition of AC electricity whose current changes direction?
Are you saying all lightning strikes change direction?
>
>
> Ground wires from any surge protector must avoid sharp
> bends. As I have so often done, a published source:
> US Army Training Manual 5-690
> 3.4 Lightning protection subsystem (p 46)
> > d.1(i) Installation of surge arresters is shown for
> > grounded and ungrounded service ... In order to prevent
> > introducing excessive inductance and resistance in the
> > transient path to the surge arrester, No. 4 AWG (minimum)
> > insulated stranded copper wire of the minimum feasible
> > length must be used to make the interconnection(s) unless
> > otherwise recommended and guaranteed by the manufacturer.
> > Also, the interconnecting wiring must not contain loops
> > or sharp bends. Otherwise, the response time of the surge
> > arrester will be delayed and a higher clamp voltage than
> > that of the surge arrester will be impressed across the
> > protected equipment, thus increasing the possibility of
> > damage. In the event a very fast transient should occur,
> > it is quite likely that the surge arrester would never
> > turn on, and all of the transient energy would be
> > dissipated by supposedly protected equipment.

I wonder why they specify insulated wire. Uninsulated wire is easier to
inspect and easier to identify as a ground. Stranded wire has less
inductance than solid, but what about flat braid? I think it's
specified for commercial transmission towers because it has less
inductance than stranded wire.

If an Army technician had thirty feet of ground wire to connect
terminals ten feet apart, he might leave the extra twenty feet taped in
a coil halfway between. I agree that a loop like that would be bad. By
comparison, how bad would it be to have a sharp bend around a wooden corner?
>
> I never said the earthing wire for a lightning rod must not
> be surrounded by a building's girders. I only said the
> preferred method of routing that earthing wire is to keep it
> outside the building. This for reasons beyond the scope of
> this discussion which is impedance, the purpose of earthing,
> and characteristics of a lightning pulse that makes it so
> challenging.
>
An external ground wire would be easy to inspect and less likely to be
damaged by humans. Are there more technical reasons?
.

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