Abstract The electric field control of insulating devices for high-voltage systems has been widely concerned, and engineering efforts are devoted to achieving the lowest possible electric field strength at a fixed system voltage, and to achieve as uniform electric field distribution as possible. Polymer materials with nonlinear conductance properties are widely used to solve the problem of electric field concentration, for example, to achieve electrical stress control of components such as cable accessory insulation, high-voltage rotating electrical machine stator system insulation, and high-power insulated gate bipolar transistors. In this paper, the method of homogenizing electric field in the application of electrical devices is introduced from two aspects of geometric stress control and nonlinear stress control. The nonlinear conductivity characteristics of inorganic fillers such as zinc oxide and silicon carbide and the formation mechanism of nonlinear conductivity of polymer matrix composites are introduced in detail. Based on the theory of percolation and interfacial conduction, the effect of doped filler content on nonlinear electrical conductivity was expounded. Taking the contact resistance of doped fillers, the number of contact interfaces, and the number of grain boundaries as the starting point, the influence mechanism of filler morphology and size on the carrier transport of nonlinear conductive composites was summarized. The application and performance control mechanism of multi-dimensional filler co-mixing and filler surface modification in the field of nonlinear conductivity materials are introduced, and the research results of nonlinear conductivity materials in high-pressure applications are summarized. It is also pointed out that the modified composite materials have complex structures and limited application in many cases, and the carrier transport mechanism has not been unified yet, so further research is still needed. The main conclusion of this paper is that the filler content in the composite has a certain impact on the formation of the nonlinear conductive seepage path, the injection of carriers and the interface effect between the filler and the matrix, thus affecting the difficulty of forming the nonlinear conductive characteristics of the composite. The influence of filler morphology mainly depends on the contact resistance between fillers. Filler size mainly affects the probability of carrier conduction path formation and is also related to interface resistance. The influence of grain size can affect the contact voltage through the number of filler contact interfaces. The filler co doping mainly regulates the difficulty of forming the conductive network structure, and the introduction of metal elements can dramatically increase the number of carriers. The surface of fillers can improve the dispersion of fillers in the matrix, thus enhancing the interaction between polymers and fillers. However, there is still no unified understanding of the influence of filler dispersion on the nonlinear electrical characteristics of composites. Nonlinear conductive materials can effectively control the electric field distribution of IGBT, GIS, cable accessories and other components, and provide guarantee for the safe operation of electrical insulation devices. It is pointed out that a lot of research is needed to broaden the range of preparation methods that can be used to synthesize nonlinear conductive composites, and improve the tensile strength and toughness of the materials. Surface modification of fillers is another relatively new research field. It can achieve uniform dispersion of high content nano fillers in polymer matrix, which is a direction that can be further studied. Polymer grafting is also an area of future research. In short, the excellent characteristics and high efficiency of emerging methods will promote the upgrading of domestic related technologies and industrial development.
Meng Zhaotong,Zhang Tiandong,Zhang Changhai等. Research Progress of Nonlinear Conductive Materials for Electrical Insulation[J]. Transactions of China Electrotechnical Society, 2023, 38(21): 5691-5711.
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