الفهرس 
1. INTRODUCTIONOnly 14 pages are availabe for public view
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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.