transformer overcurrent protection

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paul hodge

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Location
atl
I have a question on transformer overcurrent protection. Please explain when the transformer secondary does not require overcurrent protection? Primary overcurrent is based on 125% of fla of transformer? Correct? What other conditions are required?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Paul,
If you have the primary protected at 125%, then there is no protection required for the secondary of the transformer, however the secondary conductors will require protection per 240.21(C) unless this is a two wire to two wire single phase transformer or a 3 phase delta to delta transformer.
Don
 
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