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TRANSFORMER OCP NEC ART 450

TRANSFORMER OCP NEC ART 450

TRANSFORMER OCP NEC ART 450

(OP)
Hello,
I have a question concerning NEC ART 450. I want to put two xfmers in series. one is 480 to 12470 which then feeds into another that is 12470 to 208.
My question is this: how do I deal with OCP for a xfmer that is 480 on one side and 12470 on the other? Table 450.3 (A) says it is for xfmers over 600 volts.
As I interpet the NEC, I will need OCP for the primary for both xfmers (the 480 side of one and the 12470 side of the other).
Any help would be greatly appreciated.
Thanks!

RE: TRANSFORMER OCP NEC ART 450

Use the highest voltage.  

David Castor
www.cvoes.com

RE: TRANSFORMER OCP NEC ART 450

If power flow is always the same direction, the NEC requires protection at 480V feeding the first transformer, protection at 12.47 kV for the conductors to the second transformer and protection for the 12.47 kV side of the second transformer and finally 480 V protection for the transformer and 480V load cables.  The 12.47 kV protection for the cable and transformer could be the same set of fuses or circuit breaker/relay.  

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