Cableizer ®

Ambient temperature

The ambient temperature is the temperature of the surrounding medium under normal conditions, at a situation in which cables are installed, or are to be installed. It includes the effect of any local source of heat, but not the increase of temperature in the immediate neighbourhood of the cables due to heat arising therefrom.

It is essential that current ratings should be valid for the maximum temperatures given. The lower values are for winter ratings if required. The values correspond with the temperature limits of winter and summer, alternatively rainy and dry seasons. When no information about the depth of laying is given, the standard depth is to be taken as 1 m.

The following table is taken from IEC 60287-3-1 ed. 2.0

Climatein air
min
max		in 1 m
min
max
Tropical25552540
Subtropical10401530
Temperate0251020

Symbol
$\theta_a$
Unit
°C
Used in
$\alpha_{c,t}$
Transient temperature coefficient conductor material [1/K]
$\Delta \theta_{0t}$
Air temperature increase [K]
$\delta \theta_{c,\infty}$
Steady-state temperature rise conductor [K]
$\Delta \theta_{max}$
Maximum permissible conductor temperature rise [K]
$\delta \theta_{max}$
Conductor temperature rise at the end of the period of emergency loading. [°C]
$\delta \theta_{R,\infty}$
Max permissible conductor temperature rise in the steady-state [°C]
$\Delta \theta_x$
Critical soil temperature rise [K]
$I_c$
Conductor current [A]
$k_l$
Temperature rise factor in air
$k_t$
Temperature rise ratio [p.u.]
$T_{4iii}$
Thermal resistance ambient [K.m/W]
$T_{bulk}$
Bulk temperature [K]
$\theta_{at,L}$
Air temperature at outlet [°C]
$\theta_{at,z}$
Air temperature z [°C]
$\theta_c$
Temperature conductor [°C]
$\theta_{c,ins}$
Field limited conductor temperature [°C]
$\theta_{c,t}$
Transient temperature conductor [K]
$\theta_{de}$
Temperature duct outer surface [°C]
$\theta_e$
External temperature object [°C]
$\theta_{film}$
Film temperature [°C]
$\theta_{fo}$
Temperature optical fiber [°C]
$\theta_{hsj}$
Temperature protective jacket [°C]
$\theta_{init}$
Air temperature without load [°C]
$\theta_{to}$
Temperature wall (outer) [°C]
$\theta_{to,z}$
Temperature wall (outer) z [°C]
$\theta_x$
Critical soil temperature [°C]
$W_{a,L}$
Heat removed by air at outlet [W/m]
$W_{a,z}$
Heat removed by air z [W/m]
$W_{fo}$
Heat fiber optic cable [W/m]
$W_{hs}$
Heat dissipation heat source [W/m]