Abstract
In this study, Ag conductive nanoparticles were successfully grown on ZnO semi-conductive nanosheets (abbreviated as ZnO@Ag) by combined sol–gel and liquid-phase chemical reduction methods. Both ZnO and ZnO@Ag are chosen as inorganic fillers, respectively, and EPDM is used as the matrix. The microstructures and electrical performances of the EPDM-based composites with different content of fillers have been systematically investigated. The results show that no nonlinear conductivity can be observed in pristine ethylene-propylene rubber (EPDM); however, obvious nonlinear conductivity appears in ZnO/EPDM composites with 10 wt. % ZnO. Especially, after introducing 10 wt. % ZnO@Ag into EPDM, the nonlinear conductive characteristics become much more remarkable compared with 10 wt. % ZnO/EPDM. As the content of ZnO@Ag and measured temperature increase, the threshold field strength that corresponds to nonlinear conductivity decreases gradually. Besides, the increase in conductivity accompanies a decrease in breakdown field strength. Compared to pristine EPDM (breakdown strength of 133.6 kV/mm), the breakdown field strength of 30 wt. % ZnO@Ag/EPDM reduces to 75.86 kV/mm at 30 °C and 51.36 kV/mm at 70 °C. In addition, both the dielectric constant and dielectric loss gradually increase with the increase in ZnO@Ag filling content due to the semi-conductive/conductive characteristics of fillers. As a consequence, this study provides an effective way to induce nonlinear conductivity for EPDM, and ZnO@Ag/EPDM composites may be used to homogenize the electric field and improve the performances of cable accessories.
Highlights
High-voltage DC (HVDC) has the advantages of large transmission capacity, long transmission distance, low line cost, and small power loss compared with high-voltage AC (HVAC) transmission systems.1–4 As the physical foundation and key equipment for the construction of the DC power grid, the HVDC cable is an important foundation for the construction and development of the DC power grid
The results show that no nonlinear conductivity can be observed in pristine ethylene-propylene rubber (EPDM); obvious nonlinear conductivity appears in ZnO/EPDM composites with 10 wt. % ZnO
It can be seen that compared with 10 wt. % ZnO/EPDM, much more inorganic fillers can be observed in the cross-sectional image of 30 wt. % ZnO@Ag/EPDM, the dispersion of ZnO@Ag fillers is still uniform without obvious agglomeration, and no obvious interfacial defects such as cracks and voids can be observed, which lays a good foundation for the following test
Summary
High-voltage DC (HVDC) has the advantages of large transmission capacity, long transmission distance, low line cost, and small power loss compared with high-voltage AC (HVAC) transmission systems. As the physical foundation and key equipment for the construction of the DC power grid, the HVDC cable is an important foundation for the construction and development of the DC power grid. The improvement effect of this solution is limited and will increase the manufacturing cost and operating cost.7 Another method is to change the properties of the insulation materials of cable accessories to solve the problem of uneven electric field distribution. Field grading material with good nonlinear electrical conductivity can be used to alleviate local electric field concentration, and the electric field parameters can be changed intelligently as the electric field changes.. Field grading material with good nonlinear electrical conductivity can be used to alleviate local electric field concentration, and the electric field parameters can be changed intelligently as the electric field changes.8–10 This method has attracted the attention and research interest of the majority of scholars. 10 wt. % ZnO/EPDM composites were studied in this work
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