Question { MSEB, 152742 }

Do you know how to measure the earth resistance? if so
explain it

Answer

The Fluke 1625 earth ground tester is able to measure earth ground loop resistances for multi grounded systems using only current clamps. With this test method, two clamps are placed around the earth ground rod or the connecting cable and each are connected to the tester. A known voltage is induced by one clamp, and the current is measured using the second clamp. The tester automatically determines the ground loop resistance at this ground rod.



Ideally a ground should be of zero ohms resistance.
There is not one standard ground resistance threshold that is recognized by all agencies.

However, the NFPA and IEEE have recommended a ground resistance value of 5.0 ohms or less.

The NEC has stated to “Make sure that system impedance to ground is less than 25 ohms specified in NEC 250.56. In facilities with sensitive equipment it should be 5.0 ohms or less.”

The Telecommunications industry has often used 5.0 ohms or less as their value for grounding and bonding.

The goal in ground resistance is to achieve the lowest ground resistance value possible that makes sense economically and physically.