Never heard of a transformer having a short circuit rating. Can't even imagine what a transformer short circuit rating might be. The only way to evaluate a transformer is the damage curves.
25 to 40 times the base current per Table 16 of C57.12.00, depending on kVA. Applies to all distribution transformers up to 600 V secondary, so most padmounts are included.
I believe xfmrs complying with ANSI C57.12.xx need to meet short circuit requirements. decades ago (back in the day), I designed these and they were tested. Several shots including long duration, short and asymmetrical were required. The basic rating though I believe was derived as 1/(Per Unit Z). So for example a 4% xfmr would have 25 times rated short circuit capability.
1/Z would mean the current is limited only by the transformer impedance. That rule applies to Category II transformers. Categories III and IV are limited by the transformer impedance plus the user specified system impedance. If the user fails to specify an impedance, values from Table 18 are used. Of course a user always has the option to specify zero impedance. Category I transformers have tabulated values as stated above.
As far as duration:
Category I: t=1250/I^2 where I is the multiple of base current
Categories II through IV: t=2s
