Steve,
I am curious as to why all the building lightning rod systems I have seen on
barns and homes use stranded wire in a rope lay, from the rod to the ground
field?
Harger Lightning Protection sells many sizes of multi strand bonding
conductors. They identify them with their cross-sectional area measured in
cm. I also have a few Andrews hardline grounding kits that use stranded
wire.
Perhaps manufacturers sacrifice some performance for flexibility?
----- Original Message -----
From: <K7LXC@aol.com>
To: <ewing@alum.mit.edu>; <towertalk@contesting.com>
Sent: Tuesday, July 30, 2002 8:32 AM
Subject: Re: [Towertalk] Ground wire impedance
> In a message dated 7/29/02 10:26:52 AM Pacific Daylight Time,
> ewing@alum.mit.edu writes:
>
> > 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
> > cable
> > -- 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.)
>
> Two things. First, stranded wire is NOT acceptable for ground systems.
> Each strand will oxidize and then the strands will be electrically
insulated
> from each other. Use solid wire or copper strap only.
>
> Next, while the multi-strands do offer more surface area over single
> strand, if you need more earth contact you should use copper strap instead
of
> the multi-strand stuff. Using copper strap in rocky or other poor earth
> conditions instead of wire is a good way to improve the effectiveness of a
> potentially poor ground system. Another poor earth technique is to lay
ground
> rods horizontally if you can't get them in vertically.
>
> Cheers,
> Steve K7LXC
> TOWER TECH
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