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Ground Fault at 208V switchboard

Ground Fault at 208V switchboard

Ground Fault at 208V switchboard

(OP)
The lighting switchboard is derived via 480V/208V transformer from 480V main switchboard. The transformer is DYn and the secondary is solid grounded.
I'd like to use 208V line-line voltage to small motor and 120V phase-neutral to lighting fitting each.
 Both feeder breakers on lighting switchboard(208V,3ph) will open against ground fault ?
 

RE: Ground Fault at 208V switchboard

You don't show the transformer neutral being connected to ground (which it normally must be). If the neutral is grounded, the branch circuit breakers will open for ground faults.

RE: Ground Fault at 208V switchboard

In NEC land, to serve line to neutral loads, the neutral must be solidly grounded.  No ifs, no ands, no buts.  With a solidly grounded neutral circuit B would only need a single pole breaker.  Also, in NEC land, there are very few, extremely specialized, exceptions to the rule that a 208Y system shall be solidly grounded.

Elsewhere in the world other rules may apply, but your voltages strongly suggest that the NEC or a very similar code will govern.

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