In recent years, dry-type air-core reactors have frequently experienced inter-turn short circuits due to the aging of the inter-turn insulation. In this paper, we prepared epoxy/glass fiber samples and carried out an accelerated thermal aging test up to 840 hours. In different stages of aging, we tested the surface insulation properties, dielectric properties, thermal and mechanical properties of the samples. The results show that: Flashover voltage drops significantly, and when aging for 35 days, it has dropped by 12.4%. This is because aging is accompanied by the conversion of shallow traps to deep traps and the reduction of conductive channels, which slows down the charge dissipation rate and decreases the flashover voltage. Dielectric, thermal, and mechanical properties also show a deteriorating trend. Through the analysis of the changes in thermal and mechanical properties, it is inferred that thermal aging will damage the epoxy matrix more than the glass fiber. In addition, combined with the scanning electron microscope, Fourier transform infrared spectrometer, and X-ray photoelectron spectrometer characterization results, we believed that the main reason for the material deterioration is the detachment of the glass fiber and the break of the long chain of the matrix. This article has certain reference value for the subsequent engineering application and online monitoring of this material.
Alumina/epoxy resin (Al 2 O 3 /EP) composite material is widely used in the manufacture of insulators. However, the operation environment of long-term high-voltage direct current will destroy Al 2 O 3 /EP surface insulating performance. In this article, Al 2 O 3 /EP was modified by atmospheric pressure Ar and Ar/CF 4 plasma jet, and its aging effect was studied by investigating the physicochemical characteristics and the electrical performances of the sample 0 $ 100 days after modification. The experimental results show that after plasma treatment the surface roughness of the material increases; the O/C ratio on the surface of the material increases after Ar treatment, and the F element is grafted on the surface after Ar/CF 4 treatment. These changes lead to the increase of surface energy and hydrophilicity, and the improvement of electrical performance. The surface properties change within 100 days owing to the oxidation reactions and the variability of recombination chemical bonds and molecular chains after high-energy plasma treatment. The surface O/C ratio of the materials treated by Ar plasma is obviously reduced, the hydrophobicity is restored to some extent, and the electrical properties are also obviously weakened. In comparison, the properties of Ar/CF 4 plasma-modified materials do not change significantly.
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