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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