Research On The Design And Improvement Of UHV Carbon Fiber Closed Clamp

The closed clamp is the most commonly used tool to replace the porcelain or glass insulator of the transmission line.In the use process,it takes the place of the original insulator piece to bear the vertical load of the hanging point,so it needs to have high mechanical strength.At present,the closed fixture is mainly processed by two materials:aluminum alloy and titanium alloy.However,with the increase of voltage level(more than500 k V),insulator size and weight become larger,conductor load increases,aluminum alloy closed clamp is no longer applicable due to its low strength,and titanium alloy closed clamp becomes the first choice.However,in UHV transmission lines,due to the increase of conductor load and span,the titanium alloy closed clamp can meet the strength requirements,but its weight has reached more than 27 kg,which is very inconvenient for workers to operate,resulting in a great reduction of insulator replacement efficiency,affecting the safe and stable operation of UHV transmission lines.Therefore,it is of great significance to improve the lightweight of UHV closed fixture.Carbon fiber composite has the characteristics of high specific strength and high specific modulus,which is widely used in aircraft,automobile,sporting goods and other fields.Applying carbon fiber composite to UHV closed fixture can greatly reduce the weight of closed fixture.However,this kind of material has poor impact resistance and low interlaminar shear strength,so it is rarely used in large load-bearing components.However,for the UHV closed clamp,it needs to bear the larger bearing capacity of insulator.It is difficult to apply carbon fiber material to the design of new clamp,and the mechanical properties should meet the requirements.Therefore,this paper will design the shape structure and lay structure of UHV carbon fiber closed clamp,so that the clamp can meet the requirements of mechanical properties while achieving the goal of lightweight.In this paper,the UHV closed clamp used to replace 420 k N porcelain insulator is taken as the research object,and an UHV carbon fiber closed clamp shape structure is designed,and the laminated structure is adopted.According to the characteristics of the main bending moment and shear force of the closed fixture,the paper puts forward three commonly used bending and shear ply angles of the carbon fiber closed fixture.Based on the technical parameters of UHV closed clamp,the safety factor of UHV carbon fiber closed clamp is set as 3,that is,the maximum bearing load is 240 KN.By compiling the user subroutine USDFLD of ABAQUS and combining with the method of progressivedamage strength analysis,the strength and rigidity of three kinds of UHV carbon fiber closed clamps with different ply angles are compared and analyzed.The results show that the three ply angles of the closed fixture can not meet the strength requirements,and the failure position occurs at the ends of the two wings of the fixture,which belongs to shear failure.Based on the analysis results,this paper puts forward a kind of carbon fiber layer structure with outer layer for UHV carbon fiber closed fixture,and the thickness of outer layer is 10 mm,considering two different angles of outer layer.Based on the same analysis method,the two kinds of closed carbon fiber clamps with different angle of overlay are compared and analyzed.The results show that the closed carbon fiber clamp with an angle of overlay of ±45° bears the largest load and meets the strength requirements.In this paper,the relationship between the strength of the closed fixture and the thickness of the outer layer is further studied.The results show that there is an optimal thickness of the outer layer to maximize the strength of the closed fixture,that is,when the thickness of the outer layer is 14 mm,the load of the closed fixture is the largest.Therefore,the carbon fiber closed clamp is made of 14 mm thick cladding structure.According to the standard of DL/T 875-2016,the mechanical test of UHV carbon fiber closed clamp is carried out,and the test results meet the requirements of the standard.Through the test,the displacement load curve of the finite element calculation in the elastic deformation range is verified.After the rigidity calculation,the error between the test and the finite element rigidity is within 10%,which meets the engineering accuracy requirements.It shows the validity of the finite element analysis method and the feasibility of the structural design of the carbon fiber closed fixture in the elastic deformation range,which has important reference value for the design and mechanical performance analysis of the UHV carbon fiber tools.The lightweight effect of the carbon fiber closed clamp is obvious,which is 36.46% lighter than the UHV closed clamp used to replace 420 k N porcelain insulator.