Definition for flat with/without transposition is according to IEC 60287-1-1.The same definition can also be found in 'General Calculations Excerpt from Prysmian Wire and Cable Engineering Guide' (2015), the parameter is called $X_M$ instead of $X_s$.
Definition for variation of spacing is according to IEC 60287-1-1.
Definition for PAC/GIL is analog to cables without transposition.
$\omega \frac{\mu_0}{2\pi} \ln\left(\frac{2s_c}{d_s}\right)$ | cables without transposition |
$\omega \frac{\mu_0}{2\pi} \ln\left(\frac{2a_m}{d_s}\right)$ | cables with regular transposition |
$\omega \frac{\mu_0}{2\pi} \ln\left(2\sqrt[3]{2} \frac{s_c}{d_s}\right)$ | cables with regular transposition in equidistant flat formation (special case of the above) |
$1.25X_e$ | unknown variation of spacing between sheath bonding points |
$\frac{a_{S1} X_{e1}+a_{S2} X_{e2}+a_{S3} X_{e3}}{a_{S1}+a_{S2}+a_{S3}}$ | known variation of spacing between sheath bonding points |
$\omega \frac{\mu_0}{2\pi} \ln\left(\frac{2S_m}{D_{encl}-t_{encl}}\right)$ | PAC/GIL |