Investigation and Performance Evaluation of High Thermal Conductivity Resin for Multi-Resin Primary Insulation in Generators

The advancement of generators to elevated voltage levels and increased capacity poses significant problems to the reliability of their insulation systems, with the thermal conductivity of the primary insulation material emerging as a critical concern. This study involved the preparation of epoxy resin composites infused with individual and composite particles of silica, hexagonal boron nitride, and alumina using the melt blending process. The thermal conductivity, microstructure, dielectric properties, and breakdown characteristics of the material were assessed using a thermal conductivity meter, scanning electron microscope, permittivity test, and AC breakdown field strength experiment. The findings indicate that doping a single particle significantly enhances thermal conductivity in boron nitride and alumina, with particle size and quantity being the primary contributing factors. The multiparticle composite system has established a more comprehensive thermal conductivity network via a synergistic effect, achieving a maximum thermal conductivity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.3621 ~\mathrm{W} /(\mathrm{m} \cdot \mathrm{K})$</tex>, which is 72.42 % greater than that of pure epoxy resin. Scanning electron microscopy investigations indicated that the multi-scale particle distribution in the composite system might significantly diminish interfacial thermal resistance. Permittivity studies indicate that nano-fillers can improve interface polarization, and the dielectric characteristics of the composite filler system are markedly influenced by nano-BN. Field strength measurements indicate that a minimal quantity of silicon dioxide and 50nm boron nitride can enhance breakdown performance. While <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1 \mu ~\mathrm{m}$</tex> boron nitride in the composite system diminishes the characteristic breakdown field strength, it improves data stability. This research offers experimental foundations and theoretical guidance for enhancing the thermal conductivity of primary insulating materials in generators.