Abstract
Insulating oil modified by nanoparticle (often called nanofluids) has recently drawn considerable attention, especially concerning the improvement of electrical breakdown and thermal conductivity of the nanofluids. However, traditional insulating nanofluid often tends to high dielectric loss, which accelerates the ageing of nanofluids and limits its application in electrical equipment. In this paper, three core-shell Fe3O4@SiO2 nanoparticles with different SiO2 shell thickness were prepared and subsequently dispersed into insulating oil to achieve nanofluids. The dispersion stability, breakdown voltages and dielectric properties of these nanofluids were comparatively investigated. Experimental results show the alternating current (AC) and positive lightning breakdown voltage of nanofluids increased by 30.5% and 61%, respectively. Moreover, the SiO2 shell thickness of Fe3O4@SiO2 nanoparticle had significant effects on the dielectric loss of nanofluids.
Highlights
Adding well-dispersed nanoparticles into insulating oil can effectively improve the insulation properties and thermal conductivity of insulating oil [1,2]
Fe3 O4 @SiO2 nanoparticles: A total of 3.0 g of iron oxide was dispersed into 500 mL of ethanol and ultrasonic treated for 1 h at room temperature, 2, 4, and 8 mL of tetraethyl orthosilicate (TEOS) were added to the mixtures to obtain Fe3 O4 @SiO2 nanoparticles with different SiO2 shell thickness
Preparation of nanofluids: The three Fe3 O4 @SiO2 nanoparticles were dispersed into a type of insulating oil, the FR3 mechanized from Cargill, by ultrasonic treatment
Summary
Adding well-dispersed nanoparticles into insulating oil can effectively improve the insulation properties and thermal conductivity of insulating oil [1,2]. Grzelczak et al shows the preparation methods of gold nanoparticles with different sizes [12], and it has been proven that the nanoparticle size and morphology have an important effect on the dielectric properties of materials [13,14]. It is difficult for a single nanoparticle to meet the requirements of increasing breakdown voltage and reducing dielectric loss of insulating oil. Most of the works ignored the influences of core-shell nanoparticle size on the dielectric properties of nanofluids, and the method of prepared nanofluids with high breakdown voltage and low dielectric loss still has never been reported. The Fe3 O4 @SiO2 nanofluids showed high insulation performance as well as low dielectric loss factor, which indicates significant application in the power industry
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