Influence of paper ageing on space charge dynamics in oil impregnated insulation paper under DC electric field

The formation of space charge in oil/paper insulation system can lead to material degradation in the high electric field region and affect system reliability. The solid insulation in transformer is difficult or can not to be replaced. The influence of paper ageing on space charge dynamics in oil/paper insulation system was analyzed in this paper. The accelerated thermal aging experiment of insulation paper was conducted under 130 °C for different times. The aged papers were impregnated with the new oil to form oil/paper insulation samples. Space charge dynamics of oil/paper sample with paper aged for different times are investigated using the PEA technique under dc electric field (30kV/mm) at room temperature. The results show that with paper ageing conducted, more polar or conductive products will lead to charges easier to be injected into the oil/paper sample. The paper ageing increases the total amount of space charge injected into the sample during voltage-on process. Compared with the oil/paper sample with new paper, the maximum values of electrical field strength for oil/paper sample with seriously aged paper are more than 70 higher than its average electric field strength.