Study on AC breakdown and broadband dielectric response properties of transformer oil-based nanofluids

The research of the transformer oil-based nanofluids has been a hot topic with greater thermal conductivity and dielectric strength. Researchers haven't come to any unanimous conclusion on strengthening mechanism of insulation characteristics. In this paper, AC breakdown and broadband dielectric response properties are studied to explore the strengthening mechanism of insulation characteristics. SiO2 nanoparticles are adopted to modify the transformer oil. Compared to the pure oil, the insulation characteristic of the transformer oil-based nanofluids is improved significantly. The electric double layer structure is used to explain the phenomena and broadband dielectric response tests verify the supposition. When the carriers move forward under external electric field, their energy will be lower due to the capture of EDL. The energy of carriers will be lower continuously until the concentration reach the maximum. As a result, the breakdown voltage of transformer oil increase slightly. When the concentration continue to increase, the interface areas begin to overlap. Conducting path forms gradually so as to lower the breakdown voltage. This paper provides a new idea to explore nanoparticles modification mechanism.