Power Transformer & Switchgear Terminal marking requirement per ANSI-IEEE/NEMA Standard

[power2engineer]

I have a question about ANSI C37.20 - Switchgear standard and C57.12.70 Terminal marking for Power Transformers.

My Project involves a Low Voltage (480V, 2500A, 3 Phase) circuit breaker switchgear close coupled with a Power Transformer rated 2500KVA, 13.2KV/480V on the Right hand side of the Switchboard. I am having a debate with the manufacturer about orientation / layout of Switchgear horizontal bus and Transformer Low voltage terminal markings.

C37.20 - 6.1.1.1 (attached) Calls for Switchgear Bus lay out to be X1, X2, X3, Xo from FRONT to BACK
Where as Power Transformer Terminal marking Standard C.57.12.70 - 5.5.1 & 5.5.3 (attached) as the Transformer HV winding is non-standard on the Right side and Low voltage winding is on Left side looking from FRONT of transformer the transformer terminals should be backwards X3, X2, X1, Xo from FRONT TO REAR.

I am insisting that bus arrangement should be X1, X2, X3, Xo FRONT TO REAR for Switchgear and they should match the transformer bus arrangement same way X1, X2, X3, Xo. The manufacturers wants to reverse the Switchgear bus arrangement to match the NON-standard transformer bus arrangement of X3, X2, X1, X0.

What is the right way to do this?

 

[stevenal]

I wouldn't get too hung up on terminal numbers, it's phase designation that counts. If A phase comes off terminal 1 of the transformer and continues on to terminal 3 of the switchgear, show it clearly on the drawings and move on.