Thermal-stress-sag Coupling Power Flow Calculation and Safety Assessment of Overhead Line under Extreme High Temperature Environment

The frequent occurrence of extreme high temperature weather in summer results in a rapid increase in power grid load, heavy load or overload of power grid overhead lines or transmission channels, and poses significant challenges to the safe operation of the system. Therefore, this study investigates the relationship between high temperature meteorological conditions, conductor temperature, stress, and sag of overhead line. By incorporating the thermal-stress-sag coupling characteristic equation of overhead line into traditional power flow calculations, we enable the prediction of system power flow as well as line temperature, stress, and sag under extreme high temperature environments. Additionally, we establish safety overrun risk indexes for four types of lines to quantitatively evaluate the operational risks associated with thermal sag under extreme high temperature conditions. Finally, the effectiveness of the proposed method is verified by a modified IEEE39-bus power system.