Thanks for your comments - that's along the same lines as feedback I have had from our relay supplier.
The ratio is an exact match (1000/1), CT resistances are both quoted at 75deg C and the FLC of the circuit is around 870A. I will check with the vendor re the magnetising current of the new CT.
The reason for replacing the existing neutral CT (mounted within switchboard) is that it was damaged during modifications being made to the generator incomer cubicle.
