Transmission of 3phase output power of solar

OK kcbiibk,
Here is a rundown for you.

15KW, 32.5 amp, 3p indicates you are using 337 volts.
830 meter = 2722 ft or approx 1/2 mile

Starting with an allowable voltage drop of 5%;
this allows 16 volt drop in the line.
At 32.5 amp this would be a total of 0.492 ohm or 0.181 ohm per 1000 ft.
But since the electricity must travel both ways we must half this value
giving an allowable conductor resistance of 0.091 ohm per 1000 ft.

This indicates 0 gage Cu wire or 00 Al wire to keep voltage drop below 5% at full power.
But 0 gage Cu is not a standard size.
Even if you could find it, it would be very expensive.
2 gage is readily available but would result in approx 8% voltage drop.
00 Cu (also available) would result in 4% voltage drop.

But because of the high price of Cu these jobs are usually done with Al.
A good choice would be 2 gage Al which would result in 7% voltage drop at full power.
Any decent 3p submerged motor will have no prob at 7% voltage drop.

I recommend the wire be buried.
This is the best lightning protection you can get.
The distributed capacity of a buried cable stops voltage spikes
and will tend to suppress any ringing.

There is no start up surge when using VFDs and 3p.
Set your ramp up for some 5 seconds and your start up current will be less than the run current.

Best wishes