Re: [IRCA] Measuring "AC resistance" of ground rods to earth

[CHARLES HUTTON <charlesh3@xxxxxxx>]

Nick:
 
I have a folder of grounding info which will have some test results. I'll figure out a way to get it to you.
 
In the meantime you might want to google for "Rudy Severns grounding". He's N6LF if I recall correctly. Some of his test results appeared in QEX and also were presented at Dayton a few years ago.
 
Chuck
> Date: Wed, 18 Jul 2007 04:45:29 +0000> To: irca@xxxxxxxxxxxxxxxx> From: Nick_Hall-Patch@xxxxxxxxx> Subject: Re: [IRCA] Measuring "AC resistance" of ground rods to earth> > At 21:04 17/07/2007, you wrote:> > > -------------- Original message ----------------------> >From: Nick Hall-Patch <nhp@xxxxxxxx>> >. Most of the traditional> > > methods use power line frequencies; however, I've used the three> > > point method using an AC generator at various frequencies up to 5> > > MHz, and ended up getting really confused with the results> > > (decreasing conductivity with frequency....). Ran out of time, and> > > never went back to it.> > >> >Nick> >> >Did you mean decreasing conductivity with increasing frequency? If > >so, that's the way it's supposed to work. Otherwise, something > >weird happened if conductivity decreased at lower frequencies.> > Umm, bad phrasing there on my part, which implied the measurement of > ground conductivity.> > If I recall correctly, what the three point method measures is the > resistance between a ground rod and the earth, and with more > conductive soil, that resistance would be lower. Conductivity and > resistance are DC measurements, and the results using the three point > method and a DC source were about as expected (multiple rods gave a > low resistance, a single 8" rod gave high resistance)> > Using AC you'd actually be measuring impedance I would guess. I > believe there's capacitive reactance in parallel with that resistance > between the rod and the earth, and I'd expect that reactance to > become lower as the frequency went up, and the overall impedance would drop.> > Instead, I saw the "impedance" from rod to earth go up with > increasing frequency, so I must be misunderstanding something, or > calculating incorrectly.> > If you know of any published results for a test like this, please > refer me to it, so I can see where things went wrong (if they > did). Now to find the spare time to follow up on it.> > best wishes,> > Nick> > > > > > __________________________________
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