Is a 3-phase transformer bank considered 3 separately derived systems?

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CelectricB

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Location
Texas Panhandle
Occupation
MEP Designer
Why is a 3-phase transformer bank not considered 3 separately derived systems & thus require a GEC for each hot? Please let me know if this question doesn't make sense and why.
 

ron

Senior Member
Although others have already made the point, I'll just add this picture to help others if need it. Try to draw out the three phases of the three phase transformer bank and where the GEC connects to. Even if it where three single phase transformers, connected as a three phase output, it would be the same.

1620779902625.png
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
450.3 Overcurrent Protection.
Overcurrent protection of transformers shall comply with 450.3(A), (B), or (C). As used in this section, the word transformer shall mean a transformer or polyphase bank of two or more single-phase transformers operating as a unit.
 
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