# Attainment factor for groups of cables

This is the attainment factor for groups of cables the cable or duct external surface, i.e. the ratio of the temperature rise at time i to the rise in the steady state.This function is used in calculating cyclic rating factor for groups of cables.

Note: The parameters $L_{cm}$ and $D_o$ are in meters.

Symbol
$\gamma_t$
Formulae
$\frac{-\operatorname{expi}\left(\frac{-{D_o}^2}{16\tau \delta_{soil}}\right)+\operatorname{expi}\left(\frac{-{L_{cm}}^2}{\tau \delta_{soil}}\right)+\left(N_c-1\right) \left(-\operatorname{expi}\left(\frac{-{d_f}^2}{16\tau \delta_{soil}}\right)+\operatorname{expi}\left(\frac{-{L_{cm}}^2}{\tau \delta_{soil}}\right)\right)}{2\ln\left(\frac{4L_{cm} F_{mh}}{D_o}\right)}$
Related
$d_f$
$D_o$
$\delta_{soil}$
$L_{cm}$
$\tau$
Used in