Three Factors That Can Change Your
“minimum” Earth Resistance:

What value of earth resistance is considered low enough? You’ll see that there’s no general rule usable for all cases. First, however, consider three factors that can change the earth electrode requirements from year to year:

1. A plant or other electrical facility can expand in size. Also, new plants continue to be built larger and larger. Such changes create different needs in the earth electrode. What was formerly a suitably low earth resistance can become an obsolete “standard.”

2. As more non-metallic pipes and conduits are installed underground, such installations become less and less dependable as effective, low-resistance ground connections.

3. In many locations, the water table is gradually falling. In a year or so, earth electrode systems that formerly were effective may end up in dry earth of high-resistance.

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