换油条件下变压器油纸绝缘老化寿命评估研究

绝缘油作为变压器油纸绝缘的重要组成部分,其绝缘性能对油纸绝缘有重要影响,变压器通过定期换油清除油中杂质以提高其绝缘性能。为探索换油周期对变压器热老化寿命变化规律的影响,对不同换油周期的变压器油纸绝缘XY模型进行130℃下加速热老化试验,并在第15 d、30 d、45 d、60 d时进行换油前后模型变温介电谱测试、绝缘纸板聚合度测试、绝缘油酸值测试等试验。通过对换油后0.01～100Hz频率段变温介质损耗曲线的绝缘油活化能与绝缘纸板活化能关系进行分析,提出了一种基于换油后中频段介电谱绝缘纸板活化能计算方法。通过上述计算方法构建老化平移因子,然后结合老化平移因子与二阶动力学模型构建不同换油周期、不同温度下的油纸绝缘结构寿命预测关系式。结果表明:随着换油周期的缩短,油纸绝缘寿命逐渐增加;根据提出的方法得到的油纸绝缘寿命预测结果与实际情况相符,验证了方法的有效性。

Aging Lifetime Evaluation of Transformer Oil-paper Insulation Considering Oil Replacement

Insulating oil is an important part of transformer oil-paper insulation,and the insulating performance of it has a significant impact on the oil-paper insulation system.The insulation performance of a transformer is improved by periodically replacement oil to remove impurities from it.We investigated the influence of oil replacement cycle on the thermal aging lifetime of a transformer.The accelerated thermal aging test at 130℃was carried out on the XY model of transformer oil-paper insulation with different oil replacement cycles,and the tests for the variable temperature dielectric spectroscopy,polymerization degrees,acid value were conducted before and after oil replacement on the 15th,30th,45th,and 60th days.The relationship between the activation energy of insulating oil and the activation energy of insulating paperboard in the frequency range of 0.01~100 Hz for variable temperature dielectric loss curve after oil replacement was analyzed in detail.A method for calculating the activation energy of insulating paperboard based on middle frequency range of dielectric spectroscopy after oil replacement was proposed,and the aging translation factor was constructed by the above calculation method.Then,combined with the aging translation factor and the second-order kinetic model,the life prediction expressions of the oil-paper insulation system under different oil replacement cycles and temperatures were established.The results show that,with the shortening of the oil change cycle,the oil-paper insulation life gradually increases.The life prediction results of the oil-paper insulation are consistent with the actual situation,which proves the effectiveness of the method.