Grounding a Separately Derived System

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Speedskater

Speedskater

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Cleveland, Ohio
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retired broadcast, audio and industrial R&D engineering
Grounding a Separately Derived System:

I have now read all of Article 250.30 twice or maybe three times and still not sure.

If a single phase isolation transformer inside a building (or residence) is wired as a 'Separately Derived System' how is it grounded?

a] To the building main GEC grounding system.
b] To a new and separate GEC grounding system.
c] Either 'a' or 'b'.

Are there any additional requirements?
 
A Separately Derived System's grounding electrode should be the nearest one of either a metal water pipe grounding electrode as specified in 250.52(A)(1) or a structural metal grounding electrode as specified in 250.52(A)(2).
If neither of those grounding electrodes are available, then any of the grounding electrodes specified in 250.52(A) can be used.

The grounding electrode conductor shall be installed per 250.30(A)(3).
 
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