Abstract
Electrodes are damaged by external forces, mechanical wear, and electrochemical corrosion during long-term operation in power systems, resulting in rough electrode surfaces. Space charge injected into the liquid by a rough electrode under a strong electric field causes electric field distortion and leads to breakdown. Moreover, the charge injection is associated with the energy barrier at the electrode-liquid interface. The combined effect mechanism of nanoparticles and electrode surface condition on the insulating characteristics of transformer oil was investigated using various surface condition aluminum plate electrodes. The breakdown voltages and space charge patterns in pure transformer oil and Al2O3 nano-modified transformer oil under impulse voltage were measured in this study through Kerr electro-optic field mapping measurement. The test results indicate that the breakdown voltage of nano-modified transformer oil depends on voltage polarity and electrode surface conditions and the charge injection shows the same mode in pure transformer oil using different surface condition electrodes, but the magnitude of charge injection differs considerably. Due to nanoparticle’s ability of shielding space charges of different polarities and the charge injection of different surface condition electrodes, they have different effects on the breakdown process of transformer oil between different surface condition electrodes. An interfacial model was formed to explore the mechanism of the effect of nanoparticles and electrode surface conditions on the insulation performance of liquid dielectrics and analyze the breakdown process using the space charge injection behaviors.
Highlights
Transformer oil with high insulation strength is widely used as an insulating material
Studies have shown that nanoparticles can effectively enhance the insulation strength of liquid dielectrics by trapping space charge, which hinders the development of streamers
We can see that the breakdown voltage of nano-modified transformer oil is higher than before modification obviously
Summary
Transformer oil with high insulation strength is widely used as an insulating material. Much research has been performed in efforts to further improve the dielectric strength of transformer oil. The complex mechanism of electrical breakdown in liquids is still not completely understood.. It has been proposed that the insulation performance of transformer oil can be improved by modification with nanoparticles. Studies have shown that nanoparticles can effectively enhance the insulation strength of liquid dielectrics by trapping space charge, which hinders the development of streamers.. The space charge restricts the dielectric breakdown strength, which is mainly reflected by charge injection and charge transfer. An electrode injects space charge into a liquid dielectric under high voltage, which affects the electric field distribution in the liquid dielectric and influences its breakdown voltage.
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