Abstract
The objective of this work was to investigate the effect of the impurities (such as metallic and carbon particles) on reducing the dielectric strength of the transformer oils. In addition, the effect of morphology, element composition, size and concentration of these impurities on reducing the dielectric strength of the transformer oils are investigated widely. The measurements of the breakdown voltage that was considered the indicator to the dielectric strength of the insulating oils were performed with different voltage types. In addition, the simulation of the particle movements in the insulating oils are carried out using constructed MATLAB script and the electric field distribution were traced using COMSOL program. Some parameters influenced on the movement of the particle in the insulating oil such as the particle shapes, the viscosity of the insulating oils, the shape of the applied voltage, and the electrode configuration. The dynamic behavior of the impurities under impulse voltage was simulated to study its motion and the influence of this motion on reducing insulating oil dielectric strength. Statistical study using the t-test was performed to determine the significance of the results and its comparison. Moreover, Weibull distribution was applied to predict the life time of the insulating oils. The DC voltage type was very danger due to the establishment of a continuous bridge between the electrodes. The impurities played an important role for reducing the dielectric strength of the insulating oil due to the field developed in the presence of impurities seemed to be non-uniform.