To study the influence of extrusion temperature on the mesoscopic morphology and comprehensive properties of high-voltage cable insulation masterbatch, and analyze its mechanism, insulating materials with different mesoscopic micro-morphologies were prepared by controlling the extrusion temperature of the insulating material. Then, combined with the microscopic characterization of the system, comprehensive electrical and mechanical performance testing, and simulation methods, the reasons for the performance differences of insulating materials are revealed and the mechanism is verified and analyzed. The results showed that at an extrusion temperature of 120 ℃, the insulation material could be fully plasticized without excessive melting, and the crystallinity and crystal size of the insulation material reached the optimal values of 42.28
In order to obtain the location information of defects in buffer layer of HV cable,at first,according to the surface morphological characteristics of buffer layer,the buffer layer states were devided into dry state,damp state,corroded state,and corroded-ablative state,and the change law of volume resistivity and relative dielectric constant during the development of defects from dry state to corroded-ablative state of buffer layer was studied via thin slice samples.Then the computing formula of the distributed capacitance and distributed conductance in the network of HV cables transmission line was derived.The feasibility of applying the FDR method to locate defects in the buffer layer of HV cables was also evaluated.Finally,a long cable experimental platform was built in the laboratory to study the effectiveness of the FDR method in locating buffer layer defects.The results show that the development of buffer layer defect mainly affects the distributed capacitance,and impedance discontinuity points generate in the process.FDR can locate the moisture and defects of the buffer layer,but the further distinction between corrosion defects and ablation defects needs to be combined with other state detection methods.
In response to the problem of uneven distribution of electric field and severe local electric field distortion in insulation partitions in high-voltage switchgear, functional material technology is introduced into the preparation of insulation partitions. Two optimization methods, internal insulation structure optimization and surface insulation structure optimization, are proposed. Based on the optimization method, a geometric model of the insulation partition is established. By changing the upper limit of the material’s dielectric constant Electric field and temperature field simulation calculations were conducted on parameters such as insulation partition thickness and surface coating thickness, and their effects on the optimization of electric field distribution were analyzed and compared. The research results indicate that compared to traditional homogeneous insulation partitions, changing the internal insulation structure and adding surface coatings can reduce the maximum field strength along the surface. When the thickness of the insulation partition increases to 12 mm, the effect is optimal, and the maximum field strength along the surface can be reduced by 69.8%; When the surface coating thickness is 1.5 mm, the effect is optimal, and the maximum field strength along the surface can be reduced by 68.5%. Finally, a comparison was made between the two optimization methods, and the differences in the effectiveness of regulating the electric field between the two were analyzed.
Aiming at the problems of large specific surface area of conventional flake boron nitride and sharp increase in resin viscosity when compounded with epoxy resin,we prepared spherical boron nitride and used it as a filler to compound with epoxy resin to prepare spherical boron nitride/epoxy composites.The preparation process and curing characteristics of spherical boron nitride/epoxy composites were studied,and the influences of the morphology and filling amount of flake/spherical boron nitride fillers on the mechanical and electrical properties of epoxy resin composites were compared.The results show that with the increase of reaction temperature,the curing degree change curve of epoxy resin shows"S"shape,and the curing process can be roughly divided into three stages of"slow-fast-slow".In terms of mechanical properties,adding a small amount of boron nitride can improve the mechanical properties of the epoxy resin composites;when the filling amount is high,spherical boron nitride/epoxy composites have better mechanical properties than flake boron nitride/epoxy composites.In terms of electrical properties,the relative dielectric constant of the epoxy resin composites increases with the increase of boron nitride content,and the dielectric loss factor is lower than 0.02;compared with the flake boron nitride/epoxy composites,the spherical boron nitride/epoxy composites have less"filler-resin"interface,lower relative dielectric constant and dielectric loss factor;adding an appropriate amount of boron nitride can significantly improve the volume resistivity and electric strength of composites.
本文综述了目前丙烯基电缆研发中的聚丙烯改性手段、电缆研发及投运情况以及聚丙烯电缆相关的规程规范,根据聚丙烯电缆研发现状,总结了聚丙烯电缆将来运行中可能遇到的问题并提出研究建议,为聚丙烯电缆后续的研究与商业应用提供参考.
