Abstract
Nano-modification is a prospective method for improving the electrical properties of transformer oil. In most situations, transformer oil combined with cellulose paper is used to construct an insulation system for power equipment, such as power transformers. However, the influence of nanoparticles on the electrical performance of oil-impregnated paper is still unclear. Therefore, in this paper, we identify the failure characteristics of both fresh and nano-modified oil/paper. Specifically, the accumulative failure characteristics of nano-oil-impregnated paper (NOIP) are experimentally determined. The space charge distribution and trap characteristics of fresh paper and NOIP were measured, and the effect of nanoparticles on the space charge behavior are then analyzed. Finally, we measure the microstructure of fresh paper and NOIP subjected to repeated impulses. The test results indicate that nano-titanium oxide (TiO2) particles have a limited effect on the breakdown voltage of NOIP. However, the particles can dramatically improve the resistant ability of NOIP against repeated impulses. For the NOIP with a nano-concentration of 0.25 g/L, the improvement reaches 62.5% compared with fresh paper. Under repeated applications of impulse voltages, the space charge density of NOIP is much lower than that of fresh paper. The deep trap density of NOIP is much higher than that of fresh OIP, whereas shallow trap density is relatively lower. Micropores are generated in paper insulation subjected to repeated impulses. The amount of the generated micropores in NOIP is lower than that in fresh paper. Nano-TiO2 particles suppress the accumulation of space charge in the oil paper insulation, which weakens the electric field distortion in the dielectric. However, nanoparticles reduce the accumulative damage caused by repeated impulses. The above two points are considered the main reasons to improve the resistant ability against repeated impulses.
Highlights
A novel approach to improving the properties of transformer oil has been developed by suspending nanoparticles in transformer oil
Nano-TiO2 particles had a limited effect on the U50 of nano-oil-impregnated paper (NOIP)
Nano-TiO2 particles can dramatically improve the resistant ability of NOIP against repeated impulses
Summary
A novel approach to improving the properties of transformer oil has been developed by suspending nanoparticles in transformer oil. The test results indicate that the insulating performance, heat dissipation performance, and anti-aging performance of nano-modified oil are improved to different degrees [1,2,3,4,5,6]. Segal et al successively found that the breakdown voltages of nano-modified transformer oils increase by different degrees (the test nanoparticles include Al2O3, TiO2, Fe3O4, SiO2, carbon nanotube and so on) [7,8,9,10,11]. The industrial application of nano-fluids still requires development due to these limitations, the application of nanoparticles in the insulation area is still considered as having potential [17,18,19,20,21]
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