Study On Anti-Flashover And Electrothermal Characteristics Of Overhead Transmission Line Insulation Drainage Line

With the rapid development of China’s power grid technology and the continuous improvement of the ecological environment,the frequent activities of birds on overhead transmission lines pose a great threat to the stable operation of the lines.The most important reason is that birds defecate and cause flashover of transmission lines.In order to reduce the occurrence of bird manure flashover accidents,this paper takes the insulated drainage line as the object,and uses the research methods of finite element simulation calculation and experimental law exploration to study the anti-bird manure flashover characteristics and electrothermal characteristics after the drainage line is coated with an insulating sheath.Firstly,this paper briefly introduces the insulation drainage line and conducts theoretical research on bird dropping flashover prevention.The theoretical calculation of electric field and temperature field involved is deduced and summarized.Secondly,the physical field simulation model of insulation drainage line is established.The influence of bird droppings and sheath parameters on the electric field distribution of insulation drainage line and the influence of insulation sheath on the temperature distribution of drainage line are studied by COMOSL Multiphysics finite element simulation software.Finally,the flashover characteristics of bird droppings and the temperature rise of the insulation drainage line were studied by simulating bird droppings with copper rods.The specific conclusions are as follows :(1)When the bird droppings are shortly connected to the cross arm,and the bird droppings are located above the drainage line,the electric field near the bottom of the bird droppings channel is distorted,and the closer to the cross arm;the closer the bird droppings are to the grading ring and the drainage line,the greater the electric field intensity at the bottom of the bird droppings,the surface of the grading ring and the drainage line.After the insulation sheath is coated,the electric field distribution near the bottom of the bird droppings and the grading ring can be greatly improved.As the thickness of the insulation sheath increases,the field strength of the grading ring and the bird droppings increases first and then decreases.As the thickness of the semiconductor layer gradually increases,the electric field on the surface of the insulation drainage line gradually decreases,while the electric field improvement near the grading ring and the bird dropping channel is not obvious.The material of the insulating layer mainly improves the electric field distribution on the surface of the insulating drainage line.The larger the relative dielectric constant,the lower the electric field intensity on the surface of the insulating drainage line.(2)As the thickness of the insulating layer increases,the heat transfer process becomes longer,and the temperature outside the insulating layer gradually decreases.The temperature inside the insulating layer is close to that of the conductor core,both of which decrease first and then increase.The thermal conductivity of the insulating layer material is an important factor affecting the temperature change and distribution of the conductor core,but it has little effect on the outer side of the insulating layer.(3)Compared with the commonly used insulation cable and insulation sheath,the insulation performance of the insulation drainage line in this paper is greatly improved.The breakdown test of insulation drainage lines with different insulation layer thickness and different semiconductor layer thickness is carried out.The test results show that the breakdown voltage increases by about 10 k V for every 1 mm increase in insulation layer thickness.After adding a semiconductor layer to the insulation drainage line,the breakdown voltage increases,and the breakdown point after breakdown is small,and the damage to the insulation drainage line is small.(4)The insulation drainage lines with different thickness and different current carrying capacity were selected in the temperature rise test.In the case of natural convection,as the thickness of the insulating layer increases,the heat dissipation area of the insulating drainage line is increased,thereby accelerating the heat dissipation;the umbrella skirt installed on the insulation drainage line is beneficial to the heat dissipation of the insulation drainage line;with the increase of current carrying capacity,the temperature of insulation drainage line increases gradually,and the accuracy of finite element simulation calculation is verified.Finally,the current carrying capacity of insulation drainage lines with different voltage levels and structures is calculated,and the simulation calculation is carried out by temperature field simulation.