Basic 3 phase question
You can't get 480V however hard you try out of a 240/415 (these days actually 230/400 nominal in Europe btw). If you have a load connected between phases and a fault occurs to Earth, it has to be on one side of the load (well, for simplicity for now) which means one side is a 240V short and the other side is just 240V through the load (so a lower current than normal), so the shorted side is your fault current to consider.

If it's somewhere inside the load (e.g. a primary transformer winding that grounds somewhere along its length) you're going to have to consider two 240V loads commoned to Earth, so 240V across each side. So if you think about it, shorting the middle of that hypothetical winding will overcurrent both sides by some relatively modest degree (in fact, 240/(415/2)) probably without tripping overcurrent protection but tripping an RCD due to the current to Earth. Which is one reason these days we have both overcurrent and RCD protection.

Forget about 480V. It just doesn't exist in a 3 phase system.