Main bonding at outbuilding

[Engineer54]

Steel armour can be used for bonding on tncs but you have to consider the heating effect of diverted neutral currents flowing through the armour as this will affect the cables ccc .

Can, but will be extremely rare, considering the CSA of the steel armouring needs to be multiplied by 8 X that of copper, ...you'll virtually never see it being used beyond that of a cables CPC...

Why would diverted neutral currents (which will only be seen at time of a fault) flowing in the armouring affect the design CCC of a cable??