A comparative analysis of dielectric properties of oil-paper insulation and polymer materials before and after thermal aging

Abstract

The shortcomings of oil-immersed transformer solid insulation like low high-temperature resistance of the insulation paper and the uneven distribution of electric field caused by the large difference of dielectric constants between insulation paper and transformer oil, restricted the development of transformer with smaller size and larger capacity. In view of this situation and the transformers demand for the dielectric physicochemical and mechanical property of insulation material, polycarbonate, polyester film and polyphenylene sulfide with high high-temperature resistance were chosen for the comparison analysis in this paper We did the 300-day thermal aging experiment on four samples in transformer oil under different aging temperatures of 90℃, 110℃ and 130℃, then analyzed the changes of their dielectric properties. The experiment results are as follows; the permittivity and dielectric dissipation factor of the three polymer materials are apparently smaller than those of the paper both before and after 300-day aging; the volume resistivity and partial discharge inception voltage of the three materials are higher than those of the paper both before and after aging; and the breakdown field strength of polycarbonate is higher than that of the paper both before and after aging, while that of polyester film and polyphenylene sulfide are slightly lower than that of the paper.