Study on aging characteristics of oil-immersed paper and polymer material based on dielectric loss

The dielectric constant and the high temperature resistant performance of solid insulation used in oil-immersed transformer would limit the capacity and size of an oil-immersed transformer. In this paper, kraft paper and polycarbonate has been aged under 90 °C, 110 °C and 130 °C up to 300 days, simultaneously an electric pre-stressing of 3 kV/mm is performed. The dielectric spectroscopy (here refer to the change tendency of tanδ along with the change of frequency and temperature) was investigated at different aging stages. The results show that the tanδ of polycarbonate are less than that of insulating paper/board under different frequency and temperature; For kraft paper, dielectric loss tanδ from 10^-2 Hz to 10⁰ Hz and dielectric loss tanδ versus temperature both can be as indicators for the degradation evaluation of insulation, but for polycarbonate only dielectric loss tanδ from 10^-2 Hz to 10⁰ Hz can be as indicators for the degradation evaluation of insulation. Meanwhile, the aging temperature is higher, the tanδ is greater.