Abstract
Despite being discovered more than 20 years ago, nanofluids still cannot be used in the power industry. The fundamental reason is that nano-insulating oil has poor stability, and its electrical performance decreases under negative impulse voltage. We found that C60 nanoparticles can maintain long-term stability in insulating oil without surface modification. C60 has strong electronegativity and photon absorption ability, which can comprehensively improve the electrical performance of insulating oil. This finding has great significance for the industrial application of nano-insulating oil. In this study, six concentrations of nano-C60 modified insulating oil (CMIO) were prepared, and their breakdown strength and dielectric properties were tested. The thermally stimulated current (TSC) curves of fresh oil (FO) and CMIO were experimentally determined. The test results indicate that C60 nanoparticles can simultaneously improve the positive and negative lightning impulse and power frequency breakdown voltage of insulating oil, while hardly increasing dielectric loss. At 150 mg/L, the positive and negative lightning impulse breakdown voltages of CMIO increased by 7.51% and 8.33%, respectively, compared with those of FO. The AC average breakdown voltage reached its peak (18.0% higher compared with FO) at a CMIO concentration of 200 mg/L. Based on the test results and the special properties of C60, we believe that changes in the trap parameters, the strong electron capture ability of C60, and the absorption capacity of C60 for photons enhanced the breakdown performance of insulating oil by C60 nanoparticles.
Highlights
Numerous studies on nano-insulating oil have been conducted since Argonne Laboratory proposed the concept of nanofluids in 1995 [1]
Given that C60 particles have a certain solubility in insulating oil, surface modifiers were not used in the experiments
The average particle size of the newly prepared C60 modified insulating oil (CMIO) is 305.7 nm, and the average particle size of the CMIO kept for 12 months is 320.1 nm
Summary
Numerous studies on nano-insulating oil have been conducted since Argonne Laboratory proposed the concept of nanofluids in 1995 [1]. No nano-insulating oil that can be used in the power industry has been discovered owing to the constraints caused by the following factors. Matching surface modifiers must be used to ensure the long-term stability of these nanoparticles [2,3,4]. Surface modifiers may deteriorate and fall off in long-term complex environments (such as heat, electricity, and magnetism), which weaken the dispersion of nanoparticles. An improper amount of surface modifier may adversely affect the viscosity, as well as the physical and chemical stability, of the modified oil and even the heat transfer performance of nanoparticles [4]
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