Analysis Of Equivalent Bending Rigidity Of Tensile Tower Suspension Point Conductors Based On Based On Electothermal Couping

Overhead transmission lines are prone to cracks and broken strands due to long-term vibration loads,affecting the safe operation of the power grid.Steel core aluminum stranded wire is a commonly used conductor for overhead transmission lines,and its strand structure is complex.Therefore,it is necessary to characterize its bending resistance with a "nominal" bending stiffness,that is,the Equivalent bending rigidity of overhead transmission lines.When the Equivalent bending rigidity near the suspension point of the conductor and the outlet of the fitting changes due to fatigue,the vibration level at that point will be amplified,thereby affecting the sag and air gap of the conductor.Aiming at the occurrence characteristics of transmission line breeze vibration,this thesis analyzes the Equivalent bending rigidity near the suspension point of the tension tower conductor,establishes a 3D model of the conductor,and uses a large sparse solution matrix as a calculation method to calculate the Equivalent bending rigidity of the conductor under different constraint lengths.On this basis,the influence of the number of broken strands and the displacement of broken strands on the equivalent stiffness is further analyzed.The calculation results show that within the elastic range,the Equivalent bending rigidity of the conductor decreases with the increase of the restraint length,increases with the increase of the tension,decreases with the increase of the number of broken strands,and presents a trend of first decreasing and then increasing with the increase of the displacement of broken strands.Taking the equivalent bending stiffness of the wire at the suspension point of the tension tower at room temperature as the design value,and taking this as the starting point,according to the current IEEE standard specifications,a wire equivalent bending stiffness experimental platform is designed.LGJ-70/10 is used as the experimental wire,and through experimental testing,the equivalent bending stiffness of the wire at the suspension point of the tension tower at room temperature is obtained.Conducting electrothermal coupling calculation in the ANSYS environment,the equivalent bending stiffness of the suspension point of the tension tower wire varies with the current carrying capacity within the temperature range of-40 ℃ to 20 ℃,and is compared with the design value.Through the simulation calculation of the wire electrothermal coupling,the temperature interval of every 10 ℃ in the range of-40 ℃ to 20 ℃ under different current carrying capacities is calculated,and the characteristics of the wire temperature changing with its current carrying capacity are obtained.By setting different ampacity,through the simulation calculation and analysis of the flow field and temperature field around the conductor,the quantitative relationship between ampacity,conductor temperature and equivalent Bending stiffness in the range of-40～20 ℃ is further obtained.According to the experimental and simulation data,the equivalent Bending stiffness of the conductor decreases with the increase of the constraint length,increases with the increase of the tension,decreases with the increase of the number of broken strands,and first decreases and then increases with the increase of the displacement of broken strands.When the ambient temperature changes,the equivalent Bending stiffness of the conductor in its elastic range increases with the increase of temperature,and the conductor temperature increases with the increase of current carrying capacity,which further indicates that the equivalent Bending stiffness of the conductor decreases with the increase of current carrying capacity.