In flat formation, the separation between condcutors is the geometric mean of the three spacings ($s_{RS}$ represents the distance between the center of the phase R and phase S cable or duct).

In trefoil formation, the separation is equal to the axial spacing between the phases ($s_{c2} = s_c$).

$s_{\mathrm{c2}}$

mm

$\sqrt[3]{s_{\mathrm{RS}}s_{\mathrm{ST}}s_{\mathrm{RT}}}$