الفهرس | Only 14 pages are availabe for public view |
Abstract Oil/paper insulation system is commonly used in large oil-immersed power transformers due to its superior dielectric and mechanical properties. Surface creeping discharges frequently occurred on the oil/pressboard interface which results in producing carbonized paths, which can deteriorate the insulation system as well as decrease the transformer lifetime. Increasing the creeping flashover voltage at the oil/pressboard interface means decreasing transformer failures as well as increasing its lifetime. In this thesis, the improvement of creeping flashover voltage at nanofilled oil/pressboard interface is carried out using nanotechnology. Different nanofilled oil/pressboard insulations, as well as nanofluid samples, are prepared considering three different types of nanofiller material with different concentration levels. These nanofiller materials are Al2O3, Pb3O4, and SiO2 where each one has a nanoparticles size of 25 nm. The creeping flashover voltage test is carried out on all the prepared samples considering needle-plane electrodes configuration. The evaluation of creeping discharge at oil/pressboard interface is based on the average flashover voltage. Also, the flashover voltages at 10% and 50% probabilities are obtained based on Weibull statistical analysis. The effect of different factors such as nanofiller material types and concentration levels on the electric field distribution as well as creeping flashover voltage at oil/pressboard interface are deeply investigated. The calculation of electric field intensity distribution along nanofilled oil/pressboard interface is calculated using FEM software. In the final stage, the evaluation of breakdown strength of kraft paper impregnated in nanofilled transformer oil is carried out. Also, the insulation resistivity of this system is measured considering the same adopted nanofiller material types and concentration levels. |