| Oil-paper insulation is the main part of transformer internal insulation,and its insulation state determines the operation life of transformer.Insulating oil is an important part of oil-paper insulation of transformer,and insulation performance of insulation oil has a great influence on the insulation life of oil-paper insulation.During the actual operation of the transformer,the insulation performance is improved by periodically replacing the oil to remove impurities in the oil.However,when exploring the aging characteristics of oil-paper insulation of transformer in the laboratory,the influence of oil replacement on transformer aging is seldom considered.It will cause the laboratory aging evaluation result to be inconsistent with the actual transformer aging condition.Therefore,it is of great significance to study the oil replacement for the aging evaluation of oil paper insulation of transformersIn order to explore the influence of different oil replacement cycles on the aging characteristics of oil-paper insulation of transformer,in this paper,the dielectric spectrum experiment platform is built,the temperature dependent dielectric spectrum of oil-paper insulation structure of transformer under different oil-replacement cycles is measured.At the same time,the changing rule of the dielectric spectrum curve of the oil-paper insulation structure under different oil replacement cycles,the changing rule of the dielectric spectrum curve of the oilpaper insulation structure before and after oil replacement and the changing rule of the dielectric spectrum curve of the oil-paper insulation structure with different aging time are analyzed.Secondly,the moisture content experiment platform and polymerization degree and acid value experiment platform are built to test the physical and chemical characteristics of oil-paper insulation samples of transformers under different oil replacement cycles,the influence of different oil replacement cycles on the activation energy of pressboard was analyzed.Finally,according to the above test results,the influence of oil replacement on the aging characteristics of oil-paper insulation is clarified.In order to explore the influence of oil replacement cycles on the thermal aging life of transformer,using the theory of frequency division translation,the activation energy of pressboard in different frequencies is calculated.The results show that the activation energy calculated in different frequency bands is basically the same,and the translation factor is constructed.At last,the remaining life model of oil-paper insulation and the expression of oil replacement cycles-temperaturelife prediction are constructed by combining translation factor and cumulative loss model.Verified by calculation of experimental data,when the operating temperature of transformer is 75 ?,DP drops to 850,the remaining life of insulating pressboard is 13.89 years.When the oil replacement cycles are 3.55 years and the temperature is 73 °C,the operational life of the transformer is about 23.2 years,which is consistent with the actual service life of the transformer. |
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