13,200v transformer neutral and grounding.

[Shumake]

We have a system to install, it's a 1ph 480-13,200v step up transformer and a 13,200-120/240v step down transformer. The engineer has 3 phase coming into the first disconnect off an existing 480v transformer and pulling 1ph off disconnect for our step up transformer including 2 conductors and a ground, he then has 3conductors and ground leading from step up to step down transformer. Is the third conductor here supposed to be the neutral all the way to step down transformer? Or would we just pull the neutral off the step down transformer at our site and bond everything there? Any input will be greatly appreciated.

 

[Smart $]

Without knowing the exact HV configuration of each transformer and the wire connections, speculating one of the three wires is a neutral would be a good assumption. The next best assumption is a spare wire. Not much left to assume after that.

 

[big john]

The 120/240 transformer is a separately derived system and will create its own neutral so there'd be no reason to drag a separate one out there.

This sounds like a mistake. Seems to me it could be done with either two 15kV conductors or one 25kV concentric neutal cable and a separate equipment ground.

 

[Shumake]

on my step down transformer footprint page it shows my H and X taps but no XO tap which had me concerned.

 

[big john]

There may not be an official X0, it depends on the configuration of the transformer.

But if they are only showing 2 lowside taps I would also definitely put in an RFI about that.

 

[Shumake]

Thank you