Temperature screen/sheath

The formulae to calculate the loss factor for screen and sheath $\lambda_1$ use the resistance of the sheath $R_{sh}$ or screen $R_{sc}$ at its maximum operating temperature. Because the temperature of the sheath or screen is a function of the current, $I_c$, an iterative method is used for the calculation.

With crossing heat sources, a temperature rise of $\Delta\theta_{0x}$ applies at the hottest point.

$\theta_c-T_1 \left(W_c+\frac{W_d}{2}\right)$