有机酸对变压器油纸绝缘进一步热老化的催化作用试验研究

Experimental Study on Further Thermal Aging of Transformer Oil-paper Insulation by Organic Acid Catalysis

为研究有机酸对电力变压器油纸绝缘进一步热老化的催化作用,制作了初始水分质量分数均为0.4%的绝缘纸试样和不同类型的酸性绝缘油溶液,在室温(25℃)和90℃下,研究了酸在油纸绝缘系统中的溶解分布特性。接着在90℃下对油纸绝缘试样进行加速热老化,测试了不同老化阶段试样的绝缘纸聚合度以及油纸绝缘试样的极化去极化电流。结果表明:甲酸主要分布在绝缘纸中,并会导致纸中水分向油中扩散,硬脂酸主要分布在绝缘油中;相比于硬脂酸,甲酸极大地加速了绝缘纸的降解速率,使极化去极化电流曲线的上移幅度也更大;甲酸酸值达到0.1×10-3、硬脂酸酸值达到0.3×10-3时会对油纸绝缘进一步热老化起到明显的催化作用;在分析实际运行中影响变压器油纸绝缘热老化的因素时,需特别考虑甲酸等低分子强极性酸对油纸绝缘进一步热老化的催化作用。

To research the further thermal aging of transformer oil-paper insulation by organic acid catalysis, we prepared some insulation paper samples with 0.4% initial moisture content and different kinds of acidic insulation oil solution samples in the experiment, and investigated dissolution and distribution characteristics of acid in oil-paper insulation system at home temperature（25 ℃） and 90 ℃. Then, we accelerated thermal aging of the oil-paper sample at 90 ℃, and measured degree of polymerization of insulation paper and polarization and depolarization current of the oil-paper sample at different aging steps. Experimental results show that formic can be easily absorbed by paper while stearic can be easily dissolved in oil and formic can let moisture diffuse to oil from paper. Compared to stearic, formic accelerates the degradation rate of insulation paper obviously, and the shift-up influence of formic on polarization and depolarization current is more remarkable. The acid catalysis on further thermal aging of transformer oil-paper insulation will be obvious when the formic content reaches 0.1×10^-3 and stearic content reaches 0.3×10^-3. The influence of the acid with low molecular and strongly polar on the thermal aging of oil-paper insulation should be particularly concerned in actual analysis.