Research On Mechanical Failure Behavior Of Insulators And Fittings During Galloping Of Ultra-High Voltage Transmission Lines

With the release of the 14 th Five Year-Plan for the development of the power industry,ultra-high voltage transmission lines have emerged to address the imbalance between power supply and demand.Transmission lines may be subject to wind induced conductor galloping,which usually lasts for a long time and poses a serious threat to the operation of the power transmission system.It can easily cause major accidents such as inter phase tripping,insulator flashover,wire breakage,metal damage,and tower collapse.The flashover accidents between the tower head and the conductor caused by the oscillation of the insulator string,and the line faults caused by the failure of hardware,this seriously threatening the safe operation and normal power supply of the transmission system,causing huge economic losses.Therefore,it is has great significance to analyze the mechanical failure behavior of insulators and fittings during the galloping of ultra-high voltage transmission lines.At present,researching on insulators of different materials is mainly based on conventional performance such as tensile performance,electrical flashover,and aging performance.However,there is relatively little research on the bending bearing capacity of insulators under extreme conditions and the impact of different materials on conductor galloping;The research on fittings also focuses on wear experiments and finite element analysis of single type fittings,without comparing and analyzing fittings of different parts and functions.Therefore,this article takes experiments and simulations as the main research methods,starting from the bending strength,anti-galloping performance of insulators,and the failure and fracture problems of different hardware fittings,and is divided into three parts for research and discussion.Firstly,three-point bending tests were conducted on insulators made of ceramic,glass,and composite materials.Combined with the load displacement curve,the data was calculated and processed using formulas,and the bending strength of the three insulation materials was compared and analyzed.The bending strength of composite insulators is as high as 1092.64 MPa,which leads to the conclusion that composite insulators have the best bending performance.A macroscopic analysis was conducted on the fracture morphology of composite insulators.In addition,methods for improving the bending performance of ceramic and glass insulators have been proposed based on the material properties and structural processes of the insulators themselves.Secondly,the fracture causes of the failed fittings in practical engineering applications were discussed by means of macro morphology,scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and other characterization analysis.The fittings at the end of insulators exhibit rock sugar like cleavage characteristics,and based on the actual service status of the transmission lines,it is speculated that it is mainly cleavage fracture caused by brittle fracture under long-term tensile load;The fracture surface of the pre-twisted wire presents a large number of dimples,which is a plastic fracture feature.Because it encloses the conductor and is synchronized with the irregular galloping of the conductor in the harsh environment,it mainly bears the horizontal load,causing plastic fracture;The clamp fittings show the characteristics of brittle fracture,and the fracture position is located at the bending point of stress concentration.It is inferred that the bending position is prone to failure fracture.Finally,the finite element modeling method were introduced and establish a transmission line coupling system model considering insulator strings and spacers under wind load,detailing the values of each parameter.Based on the dynamic characteristics and galloping characteristics of the conductor,the influence of span,initial angle of wind attack,number of spans,and ice type on the galloping of the conductor is investigated,and the optimal parameters are obtained.Through the ABAQUS platform,a refined finite element model of transmission line insulator strings was established and to change the material properties of the insulators.The study found that different material insulator strings had little impact on conductor galloping and has no inhibitory effect on the wind deviation of the conductor.