I see we have another Member from Belgium, come to join us.
Welcome to ECN, jooles!.
I've never heard of a Distribution system that uses a fuse in it's Earthing conductors before.
And personally, I would think, that if the Dist. system was referenced to Earth for safety reasons, this sets a very dangerous precedent indeed!.
Should the fuse operate, you effectively lose your earth continuity and therefore any path for Fault currents.
Fusing of Earth conductors, over here, (NZ) is a practice that is dis-allowed by Regulation, in fact not even the Neutral is allowed to be fused.
I'd be very interested to see what a few of our other European members have to say on this Fused Earth system, is this a European thing?.