451 / 2022-03-15 22:45:18

Study on AC breakdown characteristics of epoxy impregnated fabric based insulation materials

epoxy impregnated fabric based insulation materials， breakdown characteristics，wettability，ac voltage，dry-type insulation

Purpose/Aim

Dry-type insulation is made of epoxy resin casting, so the epoxy wettability of fabric based insulation material and its breakdown characteristics after impregnation are the basis of design of dry-type insulation. In this paper, the epoxy wettability of three kinds of typical fabric based insulation materials, namely non-woven polyester fabric (NPF), aramid paper (AP) and Dacron-Mylar-Dacron (DMD), and their breakdown characteristics under AC voltage after impregnation were tested and analysed. The research results will provide useful opinions in material selection for dry-type insulation.

Experimental/Modeling methods

Epoxy wettability of materials were test firstly. The AC electrical breakdown strength of materials were tested using electrodes recommended by the standard GB/T 1408.1-2016. The microstructures and carbon marks of samples after breakdown for three materials were observed to explain the results.

Results/discussion

The wettability for NPF is the best, that for AP is the middle and that for DMD is the worst, which can be explained by microstructures of material. The AC breakdown strength of epoxy impregnated DMD is the highest, that of AP is the middle, and that of NPF is the lowest, but all of them are lower than that of pure epoxy resin. The reasons for differences in breakdown characteristics for the three materials are discussed in three aspects, namely the difference of relative permittivity between materials, the material structure and the anti-thermal capability of material.

Conclusions

The NPF has the best wettability, AP has the middle wettability and DMD has the worst wettability. The AC breakdown strength of epoxy impregnated DMD is the highest, that of AP is the middle, and that of NPF is the lowest, but all of them are lower than that of pure epoxy resin. The difference of relative permittivity between materials, the material structure and the anti-thermal capability of material are responsible for the differences in breakdown characteristics for the three materials under AC voltage.