this. trying to get 30A at 120V at the end of 1200' would give the op a rather large wire size (guessing 250-350 mcm)
Yes, st 120v. But, reread what I posted, 10a at either 480v or even less at ,600v.
You may want to cost out (2) 5kva transformers, one to step up from either 120 or 240 to 480v with a step back down at the other end from 480v to 120. Current for 5kva at 120v will be 41.7a (plenty) and sizing the conductor between the transformers based upon10.4a at 480v.
It may be posible for you to a also compensate for any voltage drop if the transformers included HV taps.
Stepping up to 600v may also be an option