Analytic Method to Calculate and Characterize the Sag and Tension of Overhead Lines

The mechanical behavior of overhead conductors is described by a catenary function, stress-strain relations, the relation among three types of strains, and a tension balance equation. These functions are consolidated to form a single equation. The tension of a conductor in a ruling span is determined by solving this equation. It is a polynomial function of degree 4 or less and can be easily solved in Excel or by a simple code. For some special cases, analytical solutions can be found. This method is versatile. It covers a broad range of engineering applications, such as producing a stringing chart, establishing tension-temperature relations after load, determining the effect of creep, calculating the thermal-knee point, performing auto sagging, evaluating the temperature gradient effect, etc. It is also a powerful R&D tool, providing great insight into the mechanical behavior of overhead conductors. Many interesting features of conductors can be revealed or verified by it. The method aids in the investigation of the abnormality or failure of conductors observed in the field and in laboratories.