Effects of Nanoparticle Concentration and Surfactant on Dielectric Strength of Nanofluids

Power transformers require high insulation reliability. Insulation oil is widely used in power transformers because of its high insulation performance, low dielectric constant, heat transfer constant, and so on. Many studies have aimed to enhance the characteristics of insulation oil to make it more reliable. Nanofluids are currently receiving a lot of attention for their various novel properties in this area. Nanofluids are fluids that contain nanometer-sized particles called nanoparticles. It has been reported that several insulation oils containing various types of nanoparticles have an enhanced breakdown voltage. Various mechanisms have been advocated for this enhancement. There are some issues for the practical application of the nanofluid. One of the issues is how to maintain the dispersion state of nanofluids. The breakdown voltage of nanofluids tends to decrease because of the agglomeration of nanoparticles. In this study, AC breakdown voltage measurement was performed on the mineral oil-based nanofluid. The effect of the type of nanoparticle, the nanoparticle concentration and several surfactants was evaluated with regards to suppressing the agglomeration. The results show that the breakdown voltage of the nanofluids is strongly influenced by the type of nanoparticle and the nanoparticle concentration. The surfactants of different HLB were measured to improve the dispersion state. The precipitation wasn't found by adding a surfactant in which the HLB value was 10.5. Based on the obtained results, the mechanisms of nanoparticle effect and the relation between the breakdown voltage and above factors were discussed.