Transformer secondary XO Bonding

[Jerry Albertelli]

I have a 2400V to 480V three phase Delta/Wye transformer. On the secondary side of the transformer I am feeding a 1000KVA 480V to 208V three phase delta/Wye which subsequently is feeding I-Line Panels then buildings. Do I need to bond the XO on the 2400V secondary wye side to stabilize the phases before feeding the 480V three phase Delta???
Also, on the secondary side of the three phase 208V Wye, I know that I would bond the XO, However; would I bond the two XO's from the two different transformers together??

 

[iceworm]

I have a 2400V to 480V three phase Delta/Wye transformer. On the secondary side of the transformer I am feeding a 1000KVA 480V to 208V three phase delta/Wye which subsequently is feeding I-Line Panels then buildings. Do I need to bond the XO on the 2400V secondary wye side to stabilize the phases before feeding the 480V three phase Delta???
Also, on the secondary side of the three phase 208V Wye, I know that I would bond the XO, However; would I bond the two XO's from the two different transformers together??

Educate me a bit. I've only seen a few 2400V 3ph systems. All were 2400V Delta, most floating (ungrounded), a few were corner grounded. I've never seen a 2400Y - I'm sure they are out there, I've just not seen one.

All the Y-connected 2400V windings were 4160V Y. 2400 x 1.732 = 4160

Is the MV to 2400V transformer connected as a 2400/1386 Y secondary?

ice

 

[Jerry Albertelli]

I apologize....let me rephrase. It's a 2400V Delta to 480V Wye three phase.

 

[iceworm]

...Do I need to bond the XO on the 2400V secondary wye side to stabilize the phases before feeding the 480V three phase Delta??? ...

I apologize....let me rephrase. It's a 2400V Delta to 480V Wye three phase.

Yes, I was pretty sure the transformer was 2400D primary to 480Y secondary.

What I'm asking: What is the configuration of the 2400V system feeding the transformer? I don't know where you are getting this 2400V "XO" from. Is the 2400V system a Y configuration?

ice

 

[big john]

...Do I need to bond the XO on the 2400V secondary wye side to stabilize the phases before feeding the 480V three phase Delta...?

Sounds like you're asking whether you need to bond the 480 wye feeding the 480 delta?

If you are not using a neutral conductor, no you don't need to bond the Y, check out 250.20(B) But like you said, a ground reference will stabilize your system voltages so it's definitely a good idea, and it also removes the requirement for ground-detectors.

Also, on the secondary side of the three phase 208V Wye, I know that I would bond the XO, However; would I bond the two XO's from the two different transformers together?

You wouldn't. They will be incidentally connected together by the grounding-electrode system, but it's not necessary for them to be electrically bonded to each other to work properly.

 

[Jerry Albertelli]

Thanks....That's kind of what I figured, but I wasn't sure.....