[TowerTalk] [Bulk] Re: [Bulk] Re: copper or galvanized ground rods in red SC clay

Grant Saviers grants2 at pacbell.net
Sat Jan 9 21:38:03 EST 2016


Roger,

I think I understand your point, that there are nonsense tower grounds 
with a few ohms at DC that are useless for strikes.  OTOH, I think a 
high DC resistance to "far earth ground" is not a property of a good 
lightning grounding system.

Agree that this type of meter measures essentially DC resistance 
although at several hundred Hz, selected to avoid power system 
interference & harmonics.

Agree that inductances of the tower + ground system are the controlling 
property in a strike re voltage bounce.

Assume the design follows the recommended grounding that has 2 or 3 
ground rods in multiple radial strings, with buried connecting wires.

Do you propose that it is not necessary to achieve the recommended 5 to 
10 ohms of resistance in a tower ground system?

What is your measurement technique to determine if the actual 
construction is likely to be effective?

Grant KZ1W


On 1/9/2016 14:39 PM, Roger D Johnson wrote:
>  This type of meter is designed to measure the resistance of grounds 
> at power
> line frequencies. Unfortunately, lightning is an RF phenomenon with 
> energy up
> into the Mhz range. At these frequencies, the inductance of the ground 
> system
> is more important than the resistance. Relying on this type of meter 
> to construct
> a lightning ground is not recommended.
>
> 73, Roger
>
>
> On 1/9/2016 5:11 PM, Grant Saviers wrote:
>>
>> I bought a Duoyi DY1000A Ground Resistance Tester, cost about half of 
>> what I could rent one for and 1/10 of what Greenlee wants. It seems 
>> to be very repeatable and comes with a cal loop.  For $10 more this 
>> model does more
>> http://www.ebay.com/itm/DUOYI-Leakage-Current-And-Grounding-Resistance-Clamp-on-Earth-Tester-DY1200-/321969345083?hash=item4af6de523b:g:I3MAAOxy69JTDW~A 
>>
>>
>> One thing in laying out rods is to have the wires in a radial (star) 
>> connection to the tower, no loops or cross connections. Then each rod 
>> or string of rods can be measured (actually it is a little more 
>> complicated than that, it's explained in the manual).
>>
>> Grant KZ1W
>>
>>
>>
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