Non-resistance of earth

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karl riley

Senior Member
Everyone should read Mike Holt's email about the grounding conference he went to. A very interesting article from 1884 on the use of earth as the return conductor is there in PDF to download.

It brings out the fact that due to the cross-sectional area of earth, the resistance is close to zero; almost all the impedance is in the electrode/earth surface contact. So: earth good conductor considering the infinite paths; earth/electrode impedance too high to clear a 120V fault.

Karl
 
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bphgravity

Senior Member
Location
Florida
Re: Non-resistance of earth

Hello Karl,

I read that 1884 paper and found it quite interesting. It appears to me that initial system grounding was just a convienent way to return current to the source without having to run the extra conductor. Similar to the S.W.E.R. systems you find in rural countries.

It also appears to me that alot of the grounding methods used to make Earth work as a return conductor has been kept current right up to our most recent code even though this is not the purpose of most grounding systems of today.

I love the opening statement; "To earth-dwellers, and especially to that portion of the race who are practically interested in the form of molecular motion, which we call Electricity, there is no element or adjunct of electrical science more important in many respects than the terrestrial ball itself, when we consider it in its relationship to the electrical circuit-whether that circuit be inductive or conductive, we are impelled to the opinion that its consequence cannot be too highly estimated."

No one talks like that anymore.
 
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bphgravity

Senior Member
Location
Florida
Re: Non-resistance of earth

As far as I am concerned, anything North of Tampa and East of Lake Okeechobee is a foreign country.

I figured there would be a few of these systems in the US, however I do for sure they are quite popular in places like Australia and Africa.
 
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karl riley

Senior Member
Re: Non-resistance of earth

Woodyz, I got it in a routine email from Mike. Anyone know how he could see it? I am not very web savvy.

I think it's good to get clear that the resistance is in the grounding electrode/earth interface and not in the earth itself. This distinction has not been made very clear in the past.

Yes, I appreciate the old ways of speaking also, and I envy the days when you could go into your lab or outdoors and run a few experiemnts and solve some basic scientific questions. Still can at times, though.

Karl
 
roger

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Re: Non-resistance of earth

Woodyz, and anyone else, you can read Mike's letter and download the PDF by Clicking Here .


(EDIT)BTW, you can register to receive the newsletter HERE


Roger

[ May 14, 2005, 02:03 PM: Message edited by: roger ]
 
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