We are installing a scoreboard in center field. We have to provide the 120 amp receptacle at the point of installation.

I have a 20 amp breaker located at an adjoining field.

The run would need to be 275 - 300 feet.

Depends on the load of the scoreboard, but to get an even remotely usable receptacle out there you will need at least #6cu. #4 would be better.

Better to use a higher voltage, that I am sure is available, such as 240, or perhaps 208, 277 or even 480. Would be able to use a much smaller wire, have a small 1500 or 2000 watt (VA) transformer to provide the 120 volt closer to the scoreboard.

This is what I have done on any sports field. However, this will need the consult of a qualified electrician to size and install.

The first question is what is the load? Looking for a voltage drop of no more than 5%, #8 cu at 300 ft will support a load of 13 amps. If this recpt is for the convenience of the serviceman, and will mostly support a radio or a battery charger or a drill, this should be fine. A 240/120 2kva transformer costs about $500, and needs a wire to it. 8/3 uf is about $1.50 per foot.

If you are digging a trench put three wire in it, best in conduit.