On a 75kva 3 phase transformer I use my Ugly's book to see that it is rated for 180 amps full load current. Looking at the allowable ampacities of conductors table I can see that using 75 C column and going to 180 amps that I can use 4/0 alum. or copper clad cable. When I inspected the transformer I found it to be wired with 4/0 paralled USE type cables. Was that over kill or why did they parallel the cables with 6 line conductors and 2 neutrals instead of using 3 line conductors and 1 neutral. I know it can't hurt to over size the wire (except cost and lug size in the panels). Thanks!

They problably did that because of voltage drop to a long distance load.

Codewarrior,
You are correct. I went back by there this afternoon and realized that the run is probably around 250 to 300 feet. So, they upsized to compensate for voltage drop. Thanks for the reply.

Glad I could be of help