Electrical characteristics of the pressboard modified by nano‐TiO 2 for different electrical ageing stages

In order to seek the optimal mass fraction for the modified pressboards to improve electric ageing resistance ability, the samples modified by nano‐TiO 2 with 1, 3, 5 and 7% mass fractions were made in the lab. The electrical ageing experiments were carried on these samples. The dielectric properties tests, partial discharge (PD) and DC breakdown were executed on the samples to analyse the electrical ageing performance of the cellulose pressboards modified by nano‐TiO 2 . The interface charge accumulation and decay characteristics of the samples were also tested. The nano‐TiO 2 distributions and the surface morphology for the cellulose pressboards aged 0 and 40 h were observed by scanning electron microscope (SEM) to verify the modification effect, and the trap density characteristics of unmodified and modified samples were also described. The permittivity and the conductivity properties of the modified samples are more advantageous than the unmodified ones after electrical ageing. The electrical characteristics of the modified samples are better than the unmodified ones for different electrical ageing stages. The analysis of SEM images and trap distribution give a good verification to the improvement of the modified samples for different ageing stages.