When a non-magnetic armour is present, $d$ is replaced by $d_e$ in the following formulas.

Symbol
$\Delta _{\mathrm{1}}$
Unit
-
Formulae
$\left(\frac{d_{\mathrm{s}}}{2 s_{\mathrm{c}}}\right)^{0.92 m_{\mathrm{0}} + 1.66} \left(1.14 m_{\mathrm{0}}^{2.45} + 0.33\right)$trefoil arrangement and non-flat formations
$4.7 m_{\mathrm{0}}^{0.7} \left(\frac{d_{\mathrm{s}}}{2 s_{\mathrm{c}}}\right)^{0.16 m_{\mathrm{0}} + 2}$flat formation, outer cable leading phase)
$0.86 m_{\mathrm{0}}^{3.08} \left(\frac{d_{\mathrm{s}}}{2 s_{\mathrm{c}}}\right)^{1.4 m_{\mathrm{0}} + 0.7}$flat formation, center cable phase
$- \frac{\sqrt{m_{\mathrm{0}}} \left(\frac{d_{\mathrm{s}}}{2 s_{\mathrm{c}}}\right)^{m_{\mathrm{0}} + 1} \left(0.74 m_{\mathrm{0}} + 1.48\right)}{\left(m_{\mathrm{0}} - 0.3\right)^{2} + 2}$flat formation, outer cable lagging phase)
Related
$d_{\mathrm{e}}$
$d_{\mathrm{s}}$
Used in
$\lambda_{\mathrm{1es}}$