Ground System Resistance Testing

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bkg73123

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Estimator
I need help with the following please:

Ground system design is a direct buried copper wire ground ring with ground rod every 20 feet.
Spec states: "The ground system resistance is designed to achieve no more than 10 OHMS. Testing shall be performed in accordance with industry standard resistance testing. The supplier shall provide an earth electrode subsystem with a maximum resistance to earth of 10 OHMS. Measured with a Biddle 3 Terminal device."

Question:
What test method and procedure would be used in this situation?

It sounds like they want to test the installed system resistivity to ground, which would be different than a stand alone soil resistivity test.
A soil resistivity test was performed using ASTM G-187 Sandbox Method with a result of 26,500 Ohms-cm.
I am not sure how this relates to the test I need to perform per the spec requirement.

Thank you!
 
You can consult IEEE 142 table 13 which will give the formula for resistance to ground value. It sound like the client may want a fall of potential earth ground test (three point test). I would perform a soil resistivity earth ground test (four point test).

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MrJLH said:
You can consult IEEE 142 table 13 which will give the formula for resistance to ground value. It sound like the client may want a fall of potential earth ground test (three point test). I would perform a soil resistivity earth ground test (four point test).

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Like this where the "test subject" is the entire constructed ground ring?
 
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