GUIDE FOR THERMAL RATING CALCULATIONS OF OVERHEAD LINES

The present guide provides a general method for calculating the thermal rating of overhead lines. It is intended for updating and expanding the Cigré Technical Brochure 207, which only covered the thermal behaviour of overhead conductors at low current densities (<1.5 A/mm2) and low temperatures (<100ºC), and did not consider variations in weather conditions or current with time. In the recent years, various modeling improvements have been developed that take account of these time variations and also of higher currents and higher temperatures, and these have been incorporated into the overall thermal model. Convection and solar radiation models have been improved, as well as more reliable data on the radial and axial temperature distributions, with new examples. These are key factors for the use of dynamic rating systems.