Research On The Indication Of Flashover Faults In Silicone Rubber Composite Insulators

In recent years,composite insulators are replacing porcelain and glass insulators due to their excellent water repellency and flame retardancy.This makes it particularly important to improve the efficiency of inspection work in this scenario.Electrochromic materials have been widely used in a number of fields and provide an important idea for improving the efficiency of insulator inspections.This thesis uses electrochromic materials as fillers in silicone rubber materials to provide electrochromic function and coating the surface of silicone rubber materials with insulating materials as a way of indicating flashover faults in silicone rubber.The different types of electrochromic materials have different colour change mechanisms and have different effects on the optical properties of the composite insulator material.Therefore,the selection of a stable and reliable electrochromic material that does not adversely affect the main properties of silicone rubber insulators,such as flame retardancy,water repellency and DC breakdown field strength,is essential for the study of flashover fault indication of insulators.In this thesis,basic silicone rubber materials were prepared using methyl vinyl silicone rubber as the base material for silicone rubber composites,fumed silica,hydroxy silicone oil and aluminum hydroxide as fillers,and the content of each component was adjusted to meet the performance standards for silicone rubber for insulators.The base silicone rubber material was prepared by adding non-electrochromic materials to the silicone rubber material,including the transition metal oxides vanadium pentoxide（V₂O₅）,nickel oxide（Ni O）,tungsten oxide（WO₃）and titanium dioxide（Ti O₂）,to produce a silicone rubber composite with electrochromic properties.At the same time,183 polyester insulating paint,1321 alkyd insulating paint and 921 silicone insulating adhesive were evenly and flatly applied to the surface of the silicone rubber material respectively to prepare the silicone rubber composite material coated with insulating material.The potential distribution and electric field strength of the silicone rubber composite insulator were simulated by COMSOL simulation software.The results show that under normal temperature,the insulator potential and field strength distribution is extremely uneven,and the insulator potential distribution gradually decreases from the high-voltage side to the low-voltage side,with the highest potential concentrated near the high-voltage side;under low temperature,the uniformity of potential and field strength distribution is slightly improved co Mpared with normal temperature,mainly concentrated in the uneven gas near the tips of the two end fixtures and the insulator skirt.This provides a viable basis for the application of umbrella skirt materials with flashover indication function.The silicone rubber composites were tested for basic properties,including flame retardancy,water repellency,DC breakdown field strength and broadband dielectric spectrum,to verify that the silicone rubber materials could still meet the main performance criteria of DL/T 810-2012 as composite insulator skirt materials after the addition of electrochromic materials.The results show that all the silicone rubber composites have an oxygen index of>27,which makes them flame-retardant;all the silicone rubber composites are highly hydrophobic and are basically of HC1 class;all the silicone rubber composites have a DC breakdown field strength of around 120k V/mm,which is much higher than the standard requirement of≥30 k V/mm.In this thesis the formation of a flash test system for silicone rubber composites,the design of the flash test base and the testing of flash along the face are carried out.Silicone rubber composites with different transition metal oxides and silicone rubber composites coated with different insulating materials were tested.The tests were carried out at room temperature,0°C,-20°C and-40°C respectively.It was found that the silicone rubber composites with different transition metal oxides showed different degrees of discharge traces after the flashover test and discolouration around the discharge traces on the surface of the material;the discharge traces of the silicone rubber composites coated with insulating materials were deeper and more obvious after the flashover than those of the uncoated specimens,and As the temperature decreases,the discolored traces of the silicone rubber composite become more observable,i.e.the overall performance of the flashover fault indication is enhanced.In summary,the silicone rubber compound with the appropriate amount of electrochromic material retains the properties of the silicone rubber insulator skirt material while providing observable flash fault indication,while the silicone rubber compound with the insulating material coating further enhances the observability of the discolouration marks,i.e.it has the initial flash fault indication function.