| The insulators coated with RTV(hereinafter referred to as RTV insulators)have been widely used in power transmission lines in our country for their excellent properties of hydrophobicity and anti-pollution characteristics,and both the excellent mechanical and internal insulation properties of porcelain and glass insulators.With the increase of operation years,RTV insulators are affected by environmental factors such as surface discharge,ultraviolet and contamination.It would threaten the safe operation of power system with the operation state of surface coating decreasing gradually.At present,a lot of research on the aging characteristics of RTV coating has been carried out at home and abroad.However,the change principle of physical and chemical properties of RTV coating caused by aging is not clear,and the influence of coating thickness and corona discharge strength on the aging characteristics of the coating is not clear.In order to study the aging characteristics of RTV insulator surface coating thoroughly,sampling tests for RTV insulators and corona accelerated aging tests for RTV coatings are carried out in this thesis.Then the surface state,chemical properties,dielectric properties and pollution flashover characteristics of RTV insulators and corona accelerated aging coatings are studied.The main conclusions are as follows:(1)With the increase of operation years,the surface coating of RTV insulator appeared obvious aging phenomenon,and the molecular structure and the content of the surface elements in the coating changed significantly,which led to the decrease of the hydrophobicity,chemical and dielectric properties of the coating.The aging of RTV insulator coating gradually appeared faded and shedding,the microscopic morphology observed obvious trace of powder,gullies and holes.The absorption peak of Si-O bond and Si-CH3 bond,which represented the main chain and side chain methyl of silicon rubber respectively,gradually decreased,and the content of C elements in the surface coating gradually decreased,the content of O and Si elements increased gradually.Thus,the hydrophobicity of the coating on the RTV insulator gradually decreased,the relative permittivity of the coating gradually increased,the dielectric loss tangent value increased gradually,and the volume resistivity decreased gradually.Through analyzing the correlation of aging characteristics,the appearance characteristics,hydrophobicity,FTIR absorption peak area,and dielectric loss tangent were selected to characterize the aging properties of the coating.(2)The corona discharge strength and coating thickness affected the aging speed of the coating to a certain extent.The aging speed of the coating accelerated with the increase of the corona discharge strength,and slowed down with the increase of the coating thickness.With the increase of corona discharge strength,the diameter of the surface aging area of the RTV coating increased gradually,the roughness of the coating micromorphology increased gradually,the absorption peak of Si-O bond and Si-CH3 bond gradually decreased,the content of C elements in the coating gradually decreased,and the content of O and Si elements gradually increased.Thus,the hydrophobicity of the coating gradually decreased,the relative permittivity and dielectric loss factor gradually increased,and the volume resistivity of the coating gradually decreased.The effect of RTV coating thickness on the aging properties of coatings was opposite to that of corona discharge.By analyzing the correlation of the aging characteristics,the effectiveness of the appearance characteristics,the hydrophobicity,the FTIR absorption peak area and the tangent value of dielectric loss to reflect the aging characteristics of the coating were verified.(3)The surface characteristics,chemical properties and dielectric properties of RTV coating had obvious influence on the flashover voltage of the coating.The pollution flashover voltage of the RTV coating decreased with the decrease of the hydrophobicity of the coating,decreased with the decrease of the Si-O bond and the absorption peak of the SiCH3 bond in the infrared spectrum,and decreased with the increase of the relative permittivity of the coating,and decreased with the increase of the dielectric loss of the coating,and increased with the increase of the coating volume resistivity.The intensity of corona discharge and coating thickness also affected the pollution flashover voltage of the coating.The pollution flashover voltage of the RTV coating decreased with the increase of the corona discharge strength,and the effect of corona aging on the RTV coating increased gradually.The pollution flashover voltage of the RTV coating increased with the increase of the thickness of the RTV coating,and the effect of the corona aging on the coating gradually decreased. |
