Wired up a few of these, although mostly single phase.
You need to provide earthing arrangements that would be adequate with the suppliers earth connected., but permanently connected in parallel.
All live conductors, which includes the neutral must be switched.
There should be a frequency indicator, rather than a voltage indicator connected to the generator. This either has a traffic light (red, amber, green) display or a single flashing amber light display, where the PTO speed is adjusted so that the light flashes very slowly.
These generators were usually supplied with change over switches, sized to the output of the generator. In a lot of cases these were not suitable, because the switch needs to be rated to match the maximum possible load, which was often much greater than the generator output.
An isolator should be fitted to the incoming supply before the changeover switch, which should be turned off before the C/O switch is operated. Looks like you already have this in place.
It can be handy to have an indicator lamp to show when mains power is restored.
Educate the farmer on how much tractor power these things can take. They think they take next to nothing, since the shaft can easily be turned before load is applied. Make sure they know better than to switch the C/O with the genny up to speed and a heavy load connected. I once saw a farmer do this, and the tractor was nearly flipped onto its side.
