Dynamic behavior of space charge in epoxy/metal-oxide nano-composite

Epoxy resin (EX) has been widely used as electrical insulating materials in power systems. It is important to assess the situation of EX insulating materials. As a major factor to result in the deterioration of insulating materials, the space charge behavior in the EX materials is investigated in this paper. To investigate the effect of nano segmentation on the insulation performance and space charge behavior, the testing samples were made by adding two kinds of nano-scale metal oxides into EX materials, divided by the weight ratios of 3, 5, 7 wt%. A pair of aluminum foils attached to both sides of sample surface, make the electrode pattern. After being charged by a DC power source, Thermal Step Method (TSM) was utilized to determine the charge density and electric field distribution of the samples, which involved applying a thermal step (usually 30 °C) to short-circuited insulating samples and simultaneous measurement of current response in the external circuit. The space charge density and electric field distribution can be calculated in terms of the response current. Results obtained show space charge density and electric field distribution vary according to the ratio and dispersion of nano-scale SiO₂ added into the samples, providing valuable information for the improvement of insulating materials and a novel way to qualitatively assess the dispersion of nano fillers.