Study of the Thickness Effect on the Conductive Behavior of Polymer-Based Nonlinear Insulating Dielectrics

With the swift advancement of high-voltage direct current (HVDC) transmission projects in China, the voltage levels of power systems have been continuously increasing, leading to increasingly severe challenges in terms of safety and reliability for insulation structures. Thicknesses of polymer insulation materials are usually different in various insulation structures such as HVDC cable, high-voltage bushing, cable terminations, and film capacitors. The thickness of samples prepared under laboratory conditions often differ from that encountered in real-world applications. Under such circumstances, the dielectric properties measured in the lab may not fully and accurately reflect the material's actual performance in practical environments. The equivalence or relationship between the conductive characteristics of polymer insulation materials under different thicknesses remains inconclusive. Therefore, it is pertinent to conduct research on the effects of thickness on the dielectric properties of polymerbased insulating materials. Considering the significant potential of nonlinear insulating materials in optimizing the electric field distribution of insulation structures, this paper selects silicon carbide (SiC) nanoparticles as the nonlinear filler and lowdensity polyethylene (LDPE) as the matrix material. Samples of SiC/LDPE nonlinear composites with different thicknesses were prepared by a mechanical melt-blending process. For the prepared samples with different thicknesses, the polarization current in the time-domain was measured under different electric fields, aiming to investigate the influence of sample thickness on the conductive behavior of the SiC/LDPE nonlinear composites. This study provides a certain reference for further exploring the thickness effect on the conductive behavior of dielectric materials.