Finite Element Analysis Of Connection Performance Of Overhead Transmission Line

The wire and the strain clamp assembly of overhead transmission line plays an important transmission role in the power grid,the connection performance of the aluminum conductors steel reinforced(ACSR)and the strain clamp after crimping is the guarantee for the safe operation of the line.In recent years,with the continuous advancement of transmission line construction projects in China,the transmission line crimping and overhead construction technology is gradually mature.However,during the crimping process,the ACSR breaks and the aluminum tube bulges after overhead occur from time to time,which extremely worsens the connection performance of the system and is difficult to ensure the safe service of the transmission line.Therefore,this paper takes the 630/45 wire and its matching strain clamp as the research object,deeply analyzes the typical defects of overhead line,and explores the causes of the wire crimping fracture and strain clamp bulging defects and their impact on the connection performance of the system by means of numerical analysis and test,the main work of this paper is as follows:(1)Using ABAQUS finite element simulation software,combined with the elastic-plastic deformation theory,the finite element model based on the national standard crimping method is established by using the back calculation equivalent friction method,the pressing deformation process of the wire and the strain clamp is simulated and calculated,and the accuracy of the model is verified combined with the tensile curve measured by the test.(2)Taking the installation spacing,the aluminum tube crimping length and the crimping times between the wire and the strain clamp as the analysis object,the pressing deformation process of the ACSR under different process parameters is calculated,and the effects of these process parameters on the wire fracture are compared and analyzed.The results show that too small wire installation spacing is easy to cause the fracture phenomenon of the steel core when the plastic strain increases to the fracture limit value;With the increase of the length of nonstandard aluminum tube,the pressing times of the ACSR increase,which will gradually increases the fracture risk of the ACSR;Under the same length of aluminum tube,increasing the number of crimping can make the deformation of aluminum strand more uniform and the stress of the steel core lower,which can reduce the fracture risk of the ACSR.(3)Based on the crimping model,a simplified fracture tensile model of the ACSR is established,and the influence of the ACSR fracture on the connection performance of the system is analyzed.The results show that when the ACSR is broken,the grip force of the system cannot reach the rated standard,which fully shows that the wire fracture will seriously deteriorate the connection performance of the transmission line.Therefore,in order to prevent the breakage of the wire during pressing,this paper puts forward effective preventive measures,that is,before crimping,the installation spacing between the wire and the strain clamp should be checked to ensure that the spacing is greater than 5 mm;When the crimping length of non-standard aluminum tube exceeds the qualified range specified in the national standard,the crimping times can be increased to improve the crimping fracture of the ACSR.(4)The freezing simulation test is carried out to analyze the causes of the bulging phenomenon of the connecting aluminum tube of overhead line,and the finite element model of different bulging degrees of the connecting aluminum tube is established to explore the influence of the bulging of the connecting aluminum tube on the connection performance of the system.The results show that the bulging of aluminum tube has little effect on the connection performance of the system,but the rain corrosion will weaken the mechanical strength of the steel core and affect the connection performance.Therefore,this paper formulates the defect elimination measures of injecting conductive grease in the non-pressure area,and verifies its feasibility through test.