Transformer throat connections greater than 15kV

[kewo]

What is the problem with having throat connections greater than 15kV on a transformer?

From C57.12.10-1997:
"9.6 Throat connection
A throat connection or connections may be provided for windings of 110 kV BIL (15 kV nominal system voltage) or less."

 

[7anoter4]

I don't know this ANSI standard, but there are some manufacturers supplying Non-Segregated Phase Bus Ducts up to 38 kV rated. As they declare their product is according to ANSI also. See -for instance:

http://www.farah.com.jo/pdf_BusWay/Non-Segregated Phase Bus Duct.pdf

I think you may contact them and ask this question.