Radiation shape factor for touching cables

Symbol
$\zeta_{od}$
Formulae
$\left(2-\frac{2\pi-4}{4\pi}\right) \epsilon_e$two cables touching
$\frac{3}{1-6\pi \eta_e}$three cables touching trefoil acc. to Anders 1995
$\frac{3}{1-\frac{6\pi A_e \epsilon_e \eta_{di}}{\epsilon_{di} A_{di}}}$three cables touching trefoil acc. to Anders 1997
$\frac{N_c D_o}{D_{di}} \frac{1}{1-\frac{\pi N_c D_o}{D_{di}} \frac{\epsilon_e}{\epsilon_{di}} \left(N_c-1\right) \left(1-\epsilon_{di}\right)}$n cables touching acc. to Weely 1988