I suppose that's another difference between our codes!
Here, while larger conductors are often specified, the largest wire we're ever REQUIRED to run to a ground rod is #6, which is (seat-of-pants guess here) perhaps 12mm2.
A lot has been written on the topic, but it all boils down to this question: Just what doest the ground rod do? Whatever else it does, it certainly does not help to clear faults.
