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Re: [TowerTalk] Fwd: UV and WX deterioration of THHN insulation, and eff

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Fwd: UV and WX deterioration of THHN insulation, and effects
From: Patrick Greenlee <patrick_g@windstream.net>
Date: Thu, 29 Dec 2016 07:36:56 -0600
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Hans, thanks for the pat on the back for Pat.

Why would the corroded layer conduct enough to carry a sizable amount of current when it is in parallel with good copper? Think of various resistors connected in parallel. The highest ohm values carry the least current.

Surely the skin effect doesn't force the insulation to conduct or in the case of bare wire in contact with the air does the air get "forced" to conduct by the skin effect and drive up the resultant impedance? Of course not. There is a continuum of impedances which taken in aggregate are the presented impedance of a conductor.

If anthropomorphism will help make a point lets visualize sentient electrons which when given a choice from among the various paths will tend to choose the path of least resistance making for very little current flowing in the insulation or the air next to a bare conductor. Why would these smart electrons choose to avoid the air surrounding a bare wire and avoid the insulation but flock to a corrosion product of low conductivity? Don't answer, SKIN EFFECT, as that puppy won't hunt since if skin effect could do that it would have current flowing in the insulation or the air in contact with a bare wire.

Wouldn't the current flowing in the various portions of a wire with surface corrosion exhibit current flow in the corrosion only in proportion to the inverse of its impedance? Think resistors in parallel. Does not the current apportion itself by the relative resistances of the paths such that the low value resistors get the most current and the really high value resistors get a small portion?

Patrick        NJ5G

On 12/28/2016 6:51 PM, Hans Hammarquist via TowerTalk wrote:
  I think Partick has a point. Why is the current trying to go through the 
insulating top layer of the copper wire.

Now, if you study the skin effect and apply the formulas you will find out that the skin 
effect on an insulating layer is very, very deep to the point that hardly any (actually 
non to pay attention to) is going via the insulator. Same thing with the oxidized layer 
on a bare copper wire. The skin effect "sends" all (almost) to the conducting 
copper wire. The only time there might be a problem is if the corroded layer is 
conducting enough to carry a sizable amount of current and thereby cause attenuation. I 
doubt that the THHN isolation can deteriorate to a conducting phase.

Aluminum wires have the advantage that aluminum oxide is not conducting unlike 
copper oxide, the red oxide, is.

Man, this start to be complicated. Better find that North Seeking Owl.

Hans - N2JFS

-----Ursprüngliche Mitteilung-----
Von: Patrick Greenlee <patrick_g@windstream.net>
An: towertalk <towertalk@contesting.com>
Verschickt: Mi, 28 Dez 2016 8:57 am
Betreff: Re: [TowerTalk] UV and WX deterioration of THHN insulation, and effects

Skin effect... If skin effect can force conduction into the outer limit
of the wire (the chemically altered part with poor conductivity) then
why doesn't the skin effect force conduction out into the insulation and
really have poor conduction? (or in bare wire out into the surrounding air)



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