I know it's long ago this was current, but I stumbled upon a scientific paper dealing with this matter. It's from Sri Lanka, but the theory should work for the whole world.
(Don't open this if you aren't really interested: It is a scientific paper)
http://elect.mrt.ac.lk/Lightning_IEE_99.pdf It turns out that Trumpy was right. I was wrong.
![[Linked Image]](https://www.electrical-contractor.net/ubb/redface.gif)
You need two earth rods, which are separate from the neutral. This means that the the transformer insulation is exposed to the lightning voltage and must withstand this voltage.
Apparently, lightning is reposible for many transformer failures.
