Molded insulation materials are widely used from large electric power transformer apparatus to small electrical machinery and apparatus. In this study, by adding MgO with the average particle of several tens nm and the excellent thermal conductivity into molding material, we improved the problem of insulation breakdown strength decrease according to rising temperature in overload or in bad environmental condition. We confirmed the life evaluation by using the insulation breakdown and inverse involution to investigate the electrical characteristics of nano-composites materials. By using a scanning electron microscope, it is confirmed that MgO power with the average particle size of several tens nm is distributed and the filler particles is uniformly distributed in the cross section of specimens. And it is confirmed that the insulation breakdown strength of Virgin specimens is rapidly decreased at the high temperature area. But it is confirmed that the insulation breakdown strength of specimens added MgO slow decreased by thermal properties in the high temperature area improved by the contribution of the heat radiation of MgO and the suppression of tree. The results of life prediction using inverse involution, it is confirmed that the life of nano-composites is improved by contribution of MgO according to the predicted insulation breakdown strength after 10 years of specimens added 5.0 wt% of MgO is increased about 2.9 times at RT, and 4.9 times at 100 than Virgin specimen, respectively.

This research shows the electrical characteristic using excellent epoxy nano-composite of MgO 5.0 wt% and SiO2 0.4 wt% in mechanical strength test depending on nano-additive. First of all, volume resistance depending on nano-additive and temperature using high resistance meter (HP. 4329A) by increasing 10, 100, 1,000 V of applying voltage was measured. Moreover, temperature range of 25~120℃ with virgin sample was tested using TO-9B oven by Ando Company. The result showed that virgin and the samples added with MgO and SiO2 had similar value of volume resistance in low temperature and low electric field region and reduced with slow slope. The nano-composite`s volume resistance of sample added with MgO and SiO2 had higher value than virgin sample`s volume resistance in high temperature region more than 80℃. Moreover, the slope has steeply reduced. The volume resistance of sample added with MgO 5.0 wt% was 8.38×10(13) Ω·cm and it was 6.8 times more than virgin sample in high temperature at 120℃. The insulation characteristics were constant although filler has changed in low temperature region. But, in high temperature region, the value of volume resistance of sample with MgO 5.0 wt% was 7.6 times more than the virgin sample`s volume resistance.