Study On Partial Discharge Characteristics Of Cellulose Insulation Pressboard Modified By Nano-TiO₂

Oil immersed power transformer is widely used in power system due to its advantages such as low loss,good heat dissipation and excellent insulation performance.The oil-paper insulation composite structure determines the safe and stable operation and service life of power transformer.The partial discharge?PD?is the main reason for the deterioration of oil-paper insulation of transformer.With the increasing voltage level of power grid,the damage caused by partial discharge to the oil-paper insulation inside the transformer is more prominent.Therefore,in this paper,the nano modified insulation pressboard is prepared by nano control technology to suppress the generation of partial discharge and improve the partial discharge performance of oil-paper insulation.The main research work is as follows:?1?According to the technological process of insulation pressboard production,the nano-TiO₂was used to modify the insulation pressboard in the laboratory.The modified insulation pressboard samples with different particle sizes?5nm,10nm,20nm and 30nm?and mass fractions?1%,3%,5%and 7%?of TiO₂ were prepared,and the samples were treated with vacuum oil soaking.According to the national standard,the tensile strength of the modified insulation pressboard was tested,and the surface morphology of the modified insulation pressboard was observed by scanning electron microscope?SEM?.?2?The partial discharge test platform was built.According to the analysis test results of PDIV and breakdown field strength of insulation pressboard,when the mass fraction of nano-TiO₂was 3%and the particle size was 10 nm,the PDIV and breakdown field strength of modified insulation pressboard were the highest,which were 22.8%and 25.5%higher than those of unmodified insulation pressboard.The partial discharge waveform of the modified insulation pressboard was collected.By comparing the partial discharge waveform,it was found that the partial discharge waveform of the insulation pressboard modified by nano-TiO₂ of 3%mass fraction and particle size of 10 nm was the lowest,which was 26.5%lower than that of the unmodified insulation pressboard.?3?In order to further explore the advantages of the partial discharge performance of the modified insulation pressboard with the mass fraction of nanoTiO₂ of 3%and the particle size of10 nm,the accelerated electrical aging experiment of the insulation pressboard was carried out.The partial discharge inception voltage and relative permittivity of the insulation pressboard were measured.The partial discharge pulse current and phase resolved partial discharge?PRPD?of the insulation pressboard were collected during the aging period,and the surface morphology of the insulation pressboard during the aging period was observed by SEM.The results show that nano-TiO₂ can significantly improve the partial discharge performance of insulation pressboard under electrical aging.The optimal proportion of improving the partial discharge performance of insulation pressboard is nano-TiO₂ with particle size of 10nm and mass fraction of 3%.