A 1 0kV /mm field intensity is applied to the oil-paper insulation specimen in an electrical ageing test,and ageing assessment methods for oil paper are studied in the relaxation current method.Dissolved gases in oil samples of different ageing degrees are tested through chromatography,and it is found that the gas contents before and after sample aging differ greatly from each other,which shows that samples after electrical ageing are aged to a great extent.Relaxation current tests are made on samples taken at 6 aging time points, and aging information represented by different parameters is analyzed at a different angle.First,analysis of trap distribution of the oil paper samples with the help of I*t ~log1 0t curve reveals that trap density increases gradually at the early stage of aging while trap depth increases remarkably at the late stage.Then,the current curves are fitted through the four-order Debye model,and the physical principles of these four relaxation mechanisms are deduced.These relaxation mechanisms are found to increase to different extents when aging time extends.Finally,we study how the amount of charge in depolarization periods changes with the aging time and try to use intuitive parameters to analyze aging degree at different time points.Ageing is found to start deepening substantially after 60h.%对油纸绝缘样品施加10 kV ／mm 场强进行电老化试验，并采用松弛电流法研究了油纸绝缘的老化评估方法。利用色谱法测试不同老化程度油样中的溶解气体，发现老化前后气体含量变化显著，说明经电老化的试样老化明显。分别选取6个老化时间点的样品进行松弛电流测试，从不同角度分析不同参量所表征的老化信息。利用 I*t ～log10t 曲线分析了油纸试样的陷阱分布，发现试样老化初期陷阱密度逐渐增加，试样老化后期陷阱深度明显加深。运用四阶 Debye 模型对电流曲线进行拟合，推断了油纸绝缘四种松弛机制的物理机理，发现各松弛机制随着老化时间的增加有不同程度的增大。最后研究了去极化电量随老化时间的变化趋势，试图用直观参数分析试样在不同时间点的老化程度，发现在60 h 后开始大幅度加深。
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