Space Charge Distribution Characteristics for the Oil-Paper Insulating Modified by Nano-particles Under Different Temperature Differences

Nano-TiO2 is used to improve the electrical properties of oil-paper due to its small size and large specific surface area. However, due to the characteristics of the operating conditions for the oil-paper composite insulation system, the temperature differences always exist between the internal and external surface of the oil-paper structure, and the mechanism effect of nano-TiO2 on the space charge distribution characteristics for the oil-paper under the different temperature differences is not yet clear. Therefore, the space charge and electric field distribution characteristics for the modified and unmodified samples under different temperature differences are studied by pulsed electro-acoustic method. The experimental results show that the accumulation of charges is observed inside the samples at low temperature difference, but the unmodified one is more obvious. With the increasing of the temperature differences between the internal and the outside the cellulose insulation pressboards, the accumulation of hetero charges on the anode side causes the electric field to distort for the samples, but the electric field distortion rate of the pressboard modified by nano-TiO2 is less than that of the unmodified one. As a result of the addition of nano-TiO2, the oil-paper's field strength distribution is improved due to the reduction in space charge accumulation.