Uprating of 400 kV overhead lines using conductor temperature sensors and ambient weather stations

The study aimed to evaluate the impact of topography on the current DLR approach, investigate additional ampacity potential, and validate the DLR methodology both with and without incorporating a yearly solar radiation profile. Results indicate that the existing DLR methodology increases the ampacity by an average of 35 % for the 400 kV line and 31 % for the 220 kV line, without exceeding the maximum permissible conductor temperature of 80°C. Incorporating the time-dependent global radiation profile further increases ampacity by 43 % and 46 % for the 400 kV and 220 kV lines, respectively. This enhancement is most pronounced during nighttime and winter periods when actual radiation is below the constant 900 W/m² previously assumed.

Although this extension introduces a higher risk of overestimation of ampacity, the analysis shows that thermal limits would not have been exceeded even under (n–1) contingency conditions. Therefore, the DLR approach can be safely expanded to include global radiation variability, provided that ongoing verification accompanies its implementation.