Tech referance on MV clearance in substations?

[hfrish]

I am looking for a source to referance on the standards for safe clearance of MV equipment energized parts (2300v)in a substation. How low can this voltage bus be installed and still be safe for people entering the sub.

I have a transformer with 2300vac primary and side mounted bushings. THe bus is insulated now but I want to referance a standard for clearance or a standard for limiting access.
Please advise.

 

[busbar]

In ANSI regions where the [1999] National Electrical Code prevails, Articles 110 part C and 490 specify various dimensions and guarding.