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What is the permissible value of earth resistance!
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Answer Posted / rajkumar.d
There is a good deal of confusion as to what constitutes a
good ground and what the ground resistance value needs to
be. 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 recom- mended 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 sen- sitive equipment it should be 5.0 ohms
or less.”
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