纳米Al_2O_3掺杂对油纸绝缘热老化特性的影响

油纸绝缘的热老化特性是影响变压器寿命的重要因素。为获得具有优良抗热老化性能的油纸绝缘,在绝缘纸抄造的过程中掺杂纳米Al_2O_3,通过测试复合绝缘纸的电气强度确定最佳掺杂质量分数为2%。将复合绝缘纸、普通绝缘纸分别进行浸油处理,并在130℃下进行31 d的加速热老化试验,测量分析绝缘纸的工频击穿强度、介电常数、介质损耗、聚合度、抗张强度与绝缘油中糠醛含量、油的颜色、酸值、水分、粘度和油中溶解气体等参数随老化时间的变化规律。结果表明:与普通油纸绝缘相比,热老化过程中复合绝缘纸的电气性能始终优于普通绝缘纸,聚合度和抗张强度下降速度减缓,浸渍复合绝缘纸的绝缘油颜色较浅、粘度变化小,油浸复合绝缘纸的老化产物生成量少。最后提出在热老化过程中纳米Al_2O_3表面羟基能有效吸附水分、中和小分子酸,从而抑制了H+在热老化反应中的催化作用,有效延缓了油纸绝缘的热老化。

Influence of Nano-Al2O3 on Properties of Oil-Paper Insulation During Thermal Aging Process

Thermal aging property of oil-paper insulation is a key factor to affect the life of transformer.In this work,nano-Al2O3 was added to insulating paper to improve its anti-thermal aging property.The composite papers containing 2％ nano-Al2O3 were selected as samples of thermal aging test for the highest breakdown strength.The composite papers and normal papers were thermally aged at the temperature of 130 ℃ for 31 d.The variation of AC breakdown strength,dielectric property,degree of polymerization and tensile strength of insulating papers with aging time were obtained.The characteristics of insulating oil including furfural content,color,acid content,water,viscosity and dissolved gas were analyzed.The results show that,comparing with normal paper,the composite paper keeps higher electrical performance and the degree of polymerization and tensile strength of composite paper decrease more slowly during the aging process.The color of oil is lighter and the viscosity changes less in the oil impregnated composite paper.It is also found that the quantity of the thermal aging product of the oil impregnated composite paper is much less.Additionally,it is considered that the hydroxy on the surface of nanoAl2O3 can effectively adsorb H2O and neutralize low molecular weight acid in the thermal aging process,which restrained the catalysis of H + in thermal aging reaction and reduced the thermal aging of oil-paper insulation.