温度对纤维素绝缘中水分吸附和解吸的影响

doi:10.19595/j.cnki.1000-6753.tces.231704

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摘要

变压器内部温度的升降会促使水分改变其分布和聚集位置,而局部高含水量会严重影响油纸绝缘的电气强度。因此,有必要对不同温度下纤维素绝缘中水分的吸附和解吸进行研究。该文采用分子动力学的方法建立了三个不同含水量的10⁵原子量级的油-纤维素混合体系（OCS）,分别对其进行温升和温降模拟,得到了界面域和油域水分子数目（N_W）的变化规律。通过分析纤维素绝缘的溶剂可及表面积（SASA）和微观扫描电镜（SEM）图,研究了温度变化和纤维素分子劣化对纤维素绝缘中水分吸附和解吸的影响。结果表明,高温体系反向冷却后,油域的水分子会快速迁移到纤维素域,而纤维素在高温后的不可逆劣化导致其吸附能力减弱。因此,大量的水分被滞留在界面域。对于温升模拟,温度越高,油域和界面域积累的水分越多,纤维素对水分的解吸作用越强。值得注意的是,界面域的N_W并不是一个单纯的增加趋势,而是先减后增的振荡增减趋势,温度越高,该趋势越明显。该文对油浸式电力设备的水分实时监测和绝缘性能评估具有重要的理论价值。

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关键词 ：纤维素绝缘, 水分, 吸附, 解吸, 温度, 分子模拟

Abstract：

The rise and fall of the internal temperature of the power transformer will cause the moisture to change its distribution and aggregation location, and the local high moisture content will seriously affect the electrical strength of the oil-paper insulation. Most of the previous studies are limited to extracting characteristic quantities from experimental results for quantitative analysis, and lack the exploration and explanation of macroscopic experimental phenomena from the microscopic level to reflect the mechanism of the changes in the adsorption and desorption characteristics of moisture in cellulose insulating materials.
In this paper, the molecular dynamics method was used to establish three oil-cellulose mixed systems (OCS) with different water contents at the 10⁵-atom scale: in system I, the water content of the oil domain is 0.3%, while the cellulose domain does not contain water; in systems Ⅱ and Ⅲ, the water content of the cellulose domain is 3.5% and 5.7%, respectively, while the oil domain does not contain water. The whole system was divided into three regions from the Z direction: cellulose domain, interfacial domain and oil domain. Temperature rise and temperature drop simulations were carried out respectively, and the variation rules of the number of water molecules (N_W) in the interfacial domain and the oil domain were obtained. By analyzing the N_W, solvent-accessible surface area (SASA) and microscopic scanning electron microscopy (SEM) maps of the interfacial and oil domains in cellulose insulation, the effects of different temperatures on the cellulose insulation were investigated. The effect of different temperatures on the adsorption and desorption of water in cellulose insulation was investigated.
The results show that after the reverse cooling of the high-temperature system, the water molecules in the oil domain migrate rapidly to the cellulose domain, while the irreversible deterioration of cellulose after high temperature leads to the weakening of its adsorption capacity. As a result, a large amount of water is retained in the interfacial domain. For the temperature rise simulation, the higher the temperature, the more water accumulated in the oil and interfacial domains, and the stronger the desorption of water by cellulose. It is worth noting that the N_W of the interfacial domain is not a purely increasing trend, but an oscillating increasing and decreasing trend that decreases first and then increases. The higher the temperature, the more obvious the trend is. The work has important theoretical value for the real-time monitoring of moisture in oil-immersed power equipment and the evaluation of its insulation performance.

Key words： Cellulose insulation adsorption desorption moisture temperature molecular simulation

收稿日期: 2023-10-13

PACS:

TM852

基金资助:

国家电网有限公司总部科技项目资助“特高压变压器油纸绝缘微气泡沿面放电产生机制及对绝缘介电特性参量的影响研究”（5500-202116119A）

通讯作者: 赵涛男,1982年生,讲师,研究方向为电气设备在线监测与故障诊断。E-mail：t.zhao@ncepu.edu.cn

作者简介: 杨超杰男,1993 年生,博士研究生,研究方向为电气设备在线监测与故障诊断。 E-mail：1140291840@qq.com

引用本文:

杨超杰, 刘云鹏, 赵涛, 杨家骏, 刘一瑾. 温度对纤维素绝缘中水分吸附和解吸的影响[J]. 电工技术学报, 0, (): 231704-231704. Yang Chaojie, Liu Yunpeng, Zhao Tao, Yang Jiajun, Liu Yijin. Effect of Temperature on Moisture Adsorption and Desorption in Cellulose Insulation. Transactions of China Electrotechnical Society, 0, (): 231704-231704.

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