Appendix 4, section 6.1 equation 6

The biggest point here is that the spreadsheet you have made is simply incorrect and you should fix it. Those are not percentages for factors, and at some point, you will get the whole lot VERY muddled if you carry on like this. The various rating factors are decimal fractions of unity, if you want to use percentages the tabulated numbers must be multiplied by 100 so 0.82 becomes 82%. I would stay away from percentages if I were you because they are the least understood “simple” mathematical concept in the world. Even our dear Government and the BBC don't realise that a percentage change of a small number is still a small number, 382% increase of 10 is only 38.2, but of course, it sounds huge to make an impact, particularly if it is Covid deaths! Because of the low current in your cable, the temperature rise will be essentially zero. The rise is not linear with increasing current, because the cable resistance also increases with temperature. In your case, low current, high ambient temperature, almost all the change is due to the ambient number, very little by self-heating.

David CEng 

The biggest point here is that the spreadsheet you have made is simply incorrect and you should fix it. Those are not percentages for factors, and at some point, you will get the whole lot VERY muddled if you carry on like this. The various rating factors are decimal fractions of unity, if you want to use percentages the tabulated numbers must be multiplied by 100 so 0.82 becomes 82%. I would stay away from percentages if I were you because they are the least understood “simple” mathematical concept in the world. Even our dear Government and the BBC don't realise that a percentage change of a small number is still a small number, 382% increase of 10 is only 38.2, but of course, it sounds huge to make an impact, particularly if it is Covid deaths! Because of the low current in your cable, the temperature rise will be essentially zero. The rise is not linear with increasing current, because the cable resistance also increases with temperature. In your case, low current, high ambient temperature, almost all the change is due to the ambient number, very little by self-heating.

David CEng