Question 6.AE.1: Determine the temperature rise △Th of a single-phase transfo......
Determine the temperature rise △T_h of a single-phase transformer provided V_3=0.10\ pu=10%, T_{\mathrm{amb}}=40^{\circ} \mathrm{C} \text {, and } T_{\text {rated }}=100^{\circ} \mathrm{C} \text {. Assume } k_{\mathrm{avg}}=0.90 \text { and } \ell_{\text {avg }}=1.75
The rated temperature rise is \Delta T_{\text {rated }}=T_{\text {rated }}-T_{\mathrm{amb}}=T_{\text {rise rat }}=60{ }^{\circ} \mathrm{C}. For the harmonic with order h=3 and amplitude V_3=0.10 \mathrm{pu} \equiv 10 \%, one obtains (through linear extrapolation) the weighted-harmonic factor by replacing V_{ph}=V_{p1} by 10:
\sum_{h=3} \frac{1}{(3)^{0.9}}(10)^{1.75}=20.98resulting with Fig. 6.14 in the additional temperature increase due to the 3rd harmonic (average) \Delta T_{h=3}=3.3 \% \text { or } \Delta T_{h=3}=1.98{ }^{\circ} \mathrm{C}.
