I would be a bit wary of a 90A fuse on a 5.2A (100kVA at 11kV, 3-phase) rated transformer - especially as a 90A fuse is in all probability a back-up fuse rather than full range. All you will ever cover is a dead short on the transformer terminals - anything to deep in the transformer would risk the fuse behaving as spectacularly as the transformer when it develops a winding fault.
Bung
Life is non-linear...