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.

• For systems with three phases, we take the maximum value of the geometric mean of the spacing for any two cables, $\sqrt{s_{RS}s_{ST}}, \sqrt{s_{RS}s_{RT}}, \sqrt{s_{RT}s_{ST}}$.
• For systems with three phases and phase-split, we take the mean value between the maximum for each group, calculated as above.
• For systems with two phases and phase-split, which are usually in square arrangement, we take the mean value of the distances between the phases.

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
$D_{\mathrm{oc}}$
$d_{\mathrm{x}}$
$s_{\mathrm{c2}}$
$t_{\mathrm{sc}}$
$t_{\mathrm{scb}}$
$t_{\mathrm{scs}}$
Used in
$a_{\mathrm{m}}$
$\Delta _{\mathrm{1}}$
$\Delta _{\mathrm{2}}$
$GMD$
$\lambda_{\mathrm{0}}$
$\lambda_{\mathrm{1es}}$
$\lambda_{\mathrm{2}}$
$\lambda_{\mathrm{3}}$
$X_{\mathrm{s}}$
$X_{\mathrm{S1}}$
$X_{\mathrm{S2}}$
$X_{\mathrm{S3}}$
$y_{\mathrm{p}}$