High-temperature ampacity model for overhead conductors

A computer-based ampacity model that can predict the temperature of overhead conductors for temperatures as high as 250 C has been developed. The model is a revision of a program that has been reliably used for approximately 20 years to calculate the transient ampacity of a wide variety of conductor designs. The accuracy of the program has been determined by comparing the program predictions with temperatures that are measured on a full-scale energized outdoor test span. The accuracy of the program decreases as the average conductor temperature increases. As the conductor temperature increases, the spatial variations, both azimuthal and radial, are magnified and the task of calculating a single, average conductor temperature becomes more challenging. Typical variations in the conductor temperature were as high as 65 C in a single span when the conductor temperature approached 250 C. These temperature variations create difficulties when trying to either measure the conductor temperature with hardware attached to the line or predict the temperature with a computer-based ampacity model.