In multi-core cables, the axial separation depends on the construction of sreen and sheath.

In single-core cables, the axial separation depends on the laying: In trefoil formation, the separation is the axial spacing between the phases: $s_c = s_{cf}$ whereas in flat or individual formation, the separation is the geometric mean of the spacing between the cables or ducts.

Symbol
$s_{\mathrm{c}}$
Unit
mm
Formulae
$d_{\mathrm{x}} + t$multi-core cables with common screen/sheath
$d_{\mathrm{x}} + t + 2 t_{\mathrm{sc}} + 2 t_{\mathrm{scb}} + 2 t_{\mathrm{scs}}$multi-core cables with separate screen and common sheath
$D_{\mathrm{oc}}$multi-core cables with separate screen/sheaths
Related
$D_{\mathrm{oc}}$
$s_{\mathrm{c2}}$
$t_{\mathrm{sc}}$
$t_{\mathrm{scb}}$
$t_{\mathrm{scs}}$
Used in
$a_{\mathrm{m}}$
$\lambda_{\mathrm{1es}}$
$\lambda_{\mathrm{2}}$
$\lambda_{\mathrm{3}}$
$X_{\mathrm{s}}$
$X_{\mathrm{S1}}$
$X_{\mathrm{S2}}$
$X_{\mathrm{S3}}$