I don''t have a picture of the trans. right now ,but they are being built for us for the purpose of stepping up from 240 to 480, single phase, with the center tap on the secondary for us to be able to ground the secondary. With the 1st piece of eq. after the trans being only 3 ft. away, I'd like not to land on OC. first if possible. ( Cost $.) Just trying to clarify if I make it a GROUNDED PHASE secondary I need only primary protection. Also wanted to make sure with this grounded phase secondary we can still leave the trans. with an EQ GR along with the phase conductors and still only need primary protection.[/QUOT
Thanks for the reply. From what you are saying is that you are having a custom transformer built with a delta sec that has a center tap of which you intend to use the centertap as your ground. The one gray area that I can see is if you were to use the center tap to serve a 1ph load which I know that you are not going to but let's say that you just for grins then you would have a 3ph4w sec which requires a sec OCPD. They do this because sec currents are not seen in proportion on the primary as they would and a basic 3,ph3w.
When the centertap is used for grounding will the pri OCPD respond to an arcing or bolted ground fault accordingly? I would confirm that it would. I don"t think there would be any issues with overload protection. But I would confirm that the inst short circuit protection would respond to ground faults since you may be looking at really a 3ph4w because of your grounding the centertap where tthe pri OCPD may not respond to a ground fault.