Substitution coefficient P to calculate loss factor by circulating currents

Definition for flat arrangement is according to IEC 60287-1-1 clause 2.3.3
Definition for rectangular arrangement is according to publication 'General Calculations Excerpt from Prysmian Wire and Cable Engineering Guide' (2015)

Symbol
$P_{X}$
Formulas
$X_{e}+X_{m}$flat
$X_{e}+\frac{X_{m}}{2}$rectangular