Research On Insulation Technology Of Grading Ring Of Composite Insulator For Overhead Transmission Line

In recent years,with the relevant policies of ’ lucid waters and lush mountains are invaluable assets ’ and the continuous practice of fully implementing the development concept of harmonious coexistence between man and nature,the ecological environment has been greatly improved,and the number and scope of activities of birds have been expanding.Although overhead transmission lines have adopted a variety of bird-proof measures,due to the overlap between overhead transmission lines and the scope of bird activities,bird excretion,predation and flight activities will pose a great threat to the normal operation of transmission lines.Among the bird-related faults of transmission lines,bird manure flashover accidents account for the largest proportion,among which bird manure flashover faults caused by bird manure short-circuiting grading rings are particularly prominent.In this thesis,the insulation technology of grading ring is studied,and the air gap in the flashover process of bird droppings and grading ring is transformed into gas-solid combined gap,so as to improve the insulation performance of grading ring and reduce the probability of bird droppings flashover fault caused by grading ring,so as to reduce the bird-related accident of transmission line,which is of great significance to improve the safe and stable operation of power grid.In this thesis,the actual three-dimensional simulation model of insulation coated grading ring is established,and the influence of insulation coating medium and insulation layer thickness on the potential and electric field of composite insulator is studied.At the same time,considering the different lengths and different positions of bird droppings,the spatial electric field changes of composite insulators before and after the installation of insulation coated grading rings.Then,this thesis builds a 110 k V insulation-coated grading ring electric field test platform,and measures the spatial electric field of composite insulators under three installation methods: no grading ring,common metal grading ring and insulation-coated grading ring.Finally,this thesis conducts flashover breakdown test and ultraviolet photon number test on four samples of grading ring-coated insulating tape,plastic material,RTV silicone rubber,cross-linked polyethylene and HTV silicone rubber.The following conclusions are obtained:(1)The simulation results show that the installation of insulation-coated grading ring on composite insulators can improve the surface electric field distribution of composite insulators to a certain extent.The thicker the insulation coating layer of the insulation coating grading ring,the greater the surface electric field drop of the composite insulator;when the bird droppings are of different lengths and different positions,the insulation-coated grading ring can reduce the spatial electric field of the insulator to a certain extent,indicating that the grading ring-coated insulation layer can reduce the bird droppings flashover probability of the transmission line to a certain extent.(2)The electric field distribution of composite insulators without grading ring,common metal grading ring and insulation coated grading ring is in good agreement with the simulation results in the horizontal and vertical section directions,which verifies the influence of insulation coated grading ring on the electric field distribution of composite insulators.(3)The insulation coated grading ring can improve the breakdown voltage of the composite insulator to a certain extent,but it is affected by the insulation material itself,the coating process and the coating thickness.(4)Through the ultraviolet photon number test,it can be seen that there is little difference in the number of ultraviolet photons between the ordinary metal grading ring and the insulating coating grading ring when they are not pressurized;when different voltages are applied,the number of ultraviolet photons of the insulation-coated grading ring is less than that of the ordinary metal grading ring,indicating that the corona discharge phenomenon of the composite insulator after installing the insulation-coated grading ring is weaker than that of the ordinary metal grading ring.