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Emergency overload current

This is the current which may be applied for time $\tau$ so that the conductor temperature at the end of the period of emergency loading reaches $\theta_{max}$.

The method only holds for values of $I_2\leq2.5I_R$

Symbol
$I_{c,2}$
Unit
A
Formulas
$I_R \sqrt{\frac{{h_{1R}}^2 R_{c,1}}{R_{c,2}}+\frac{1-{h_{1R}}^2 \frac{R_{c,1}}{R_{c,2}}}{\frac{\delta \theta_{c,t}}{\delta \theta_{R,\infty}}}}$Cableizer
$I_R \sqrt{\frac{{h_{1R}}^2 R_{c,1}}{R_{c,2}}+\frac{\frac{R_{c,R}}{R_{c,2}} \left(r_{2R}-{h_{1R}}^2 \frac{R_{c,1}}{R_{c,R}}\right)}{\frac{\delta \theta_{R,t}}{\delta \theta_{R,\infty}}}}$IEC 60853-2 emergency rating
Related
$\delta \theta_{c,t}$
Transient temperature rise conductor [K]
$\delta \theta_{R,\infty}$
Max permissible conductor temperature rise in the steady-state [°C]
$\delta \theta_{R,t}$
Conductor temperature rise at time t [°C]
$h_{1R}$
Factor $h$ emergency overload
$I_R$
Max permissible steady-state conductor current [A]
$r_{2R}$
Operating point ratio [-]
$R_{c,1}$
Resistance of conductor before emergency rating [$\Omega$/m]
$R_{c,2}$
Resistance of conductor at emergency load [$\Omega$/m]
$R_{c,R}$
Resistance of conductor at max permissible steady-state rating [$\Omega$/m]
$\theta_{max}$
Highest temperature of conductor over a load variation period [°C]