Underground cable IEC 60287-1-1 1

[7anoter4]

I don't know any standard of underground laid cable ampacity calculation which would take into consideration Ground drying effect except IEC 60287-1-1.
But here is a problem. Using formula shown in 1.4.2.1 as the critical temperature rise of the soil [Dx] is added to upper part of the ratio [numerator] it seems this critical temperature rise will permit a further increasing of the current without exceling the permissible temperature. It seems very weird to me.
How is it possible increasing the [dry soil] resistance will enhance the permissible current ?

 

[juleselec]

It doesn't - if you look closely at the denominator, you will see that T4 is multiplied by v (the ratio of dry to wet soil). This has the effect of making the ampacity with partial soil drying-out lower than without it.

 

[7anoter4]

Thanks,juleselec.