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[Towertalk] Ground wire impedance

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Subject: [Towertalk] Ground wire impedance
From: (Martin Ewing)
Date: Mon, 29 Jul 2002 13:24:16 -0400
There seems to be some debate over multiconductor wire for grounding.  As I see 
it, the only advantage of stranded cable is mechanical flexibility.  I don't 
think "skin effect" (current flowing on the surface) has much to do with 
stranded wire, since the strands are all touching and are all in each other's 
magnetic fields. What is good is to maximize the surface area of the whole 
-- by making it into thin/wide strap (or hollow tube) instead of a filled 
circular cross-section, keeping the same amount of copper per foot.   That 
minimizes the inductance.  (Yes, that amounts to the skin effect argument - 
placing all the copper near the surface of the conductor.)

There's an interesting discussion of grounding (mostly medical, not lightning) 

-Martin AA6E

> From:

...First, the connection between your
> equipment ground and the outdoor ground should be a low 
> impedance ground.  I'd recommend using #4 welding cable 
> (it's what I use) rather than the 3/0 cable. The welding 
> cable is made up of about 500 strands of 30awg wire.  If 
> you do the calculation, you'll see that it has more 
> surface area (electron flow on the outside of a wire's 
> surface) than the larger but fewer strands of the 3/0).

Martin Ewing AA6E
Branford, Connecticut

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