18-24 panels per string, 120 x 250wp panels, so 6 x 20 panel strings, or 5 x 24 panel strings though 24 panels is often pushing the limit on the 1000V max Voc of the inverters.
3 phase 30 kW inverter, or more likely power-one Trio 27.4 STW with string level fuses and surge protection, or 2 x 15kW inverters.
AC cable drop needs to be under 1% at full power.
what you really need to do though is to download SMA sunny design and spend some time using that to configure the project, then just print out the pdf from that and hand it in.
Now, to actually optimise a system that's delivering 30kW AC, you'd want something more like 36kWp of panels, maybe more, but then you'd fall foul of the 30kWp limit beyond which you need to install costly export meters, and lose the automatic deemed 50% export rate, so it usually works out best to just stick with 30kWp of panels and keep the 50% deemed export payments as the factory is likely to be using more like 80-90% of the power, so gains financially from that arrangement.
ps the linked guide is out of date, you need version 3 on the MCS website.
