Delta Delta Transformer grounding

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tim89s

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Brush Prairie WA
I am installing a Delta Delta Transformer for one piece of equipment. Primary is 3 phase 480 volt, secondary is 3 phase 380 volt. I am confused about grounding the secondary. Do I need to establish a ground? If I don't establish a ground and a phase conductor goes to ground nothing will happen until another ground fault occurs, right? Do I simply take B phase to ground?

Thanks in advance
Tim
 
You can corner ground the secondary, remembering to use a white or gray wire, with no limitation on what phase you ground.
But if you leave the secondary ungrounded you are required by NEC to provide a ground detector. It does not have to take any action, just alert you so that you can fix the first fault before a second fault causes problems. There are other problems that can happen with an ungrounded system, and if you do not require it, best to avoid it.
 
I am installing a Delta Delta Transformer for one piece of equipment. Primary is 3 phase 480 volt, secondary is 3 phase 380 volt. I am confused about grounding the secondary. Do I need to establish a ground? If I don't establish a ground and a phase conductor goes to ground nothing will happen until another ground fault occurs, right? Do I simply take B phase to ground?

Thanks in advance
Tim


You can either 1, corner ground it or 2, leave it ungrounded and use a ground detector to detect faults.
 
If there are any drives involved, you might want to do some research on them as they can be particular about ungrounded and corner grounded systems.
 
If you leave it as an ungrounded system and the installation is under the rules in the NEC, you will need a ground detector per 250.21(B).
 
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