油浸纸绝缘热致气泡形成特性  

Characteristics of Thermal-induced Bubble Formation in Oil-impregnated Paper Insulation

作　　者：高萌[1] 张乔根[1] 丁玉琴[1] 王同磊 倪鹤立 袁炜雄 GAO Meng;ZHANG Qiaogen;DING Yuqin;WANG Tonglei;NI Heli;YUAN Weixiong(School of Electrical Engineering,Xi＇an Jiaotong University,Xi＇an 710049,China)

机构地区：[1]西安交通大学电气工程学院

出　　处：《高电压技术》2018年第11期3634-3640,共7页High Voltage Engineering

摘　　要：工程经验表明,对运行年限较久、受潮严重的变压器而言,绕组内部的匝间纸绝缘可在一定温度条件下析出气泡,从而危害设备绝缘。鉴于此,首先制作了纸绝缘模型,以模拟实际变压器匝间结构在水分扩散和温度变化等方面的特性,并搭建实验平台来研究气泡起始的规律。然后通过改变温升速度、含水量和溶气量等条件,研究了气泡起始温度的变化规律。研究结果表明：气泡的出现依赖一定的温度条件,若将气泡形成时刻纸绝缘的温度定义为气泡起始温度,则纸绝缘温度上升速度越快,气泡起始温度越低;而在较缓慢的温度变化下,气泡起始温度较高且分散性较大;随着温升速度的进一步下降,气泡将难以形成。反复升降温实验中,气泡形成温度逐渐升高;在此过程中,气泡通常最先从纸的压边处出现,而后可从绝缘纸表面直接析出并聚集呈簇状,表明不同条件下出现的气泡在形态和位置方面可能存在差异。随着纸绝缘中含水量的减少,气泡起始温度迅速升高,且分散性逐渐增大。气体体积分数对气泡起始温度影响较大,当油-纸系统中的气体饱和度由5%增至25%时,气泡起始温度下降20～40℃;随着气体饱和度的进一步增加,气泡起始温度开始缓慢降低,且不同含水量条件下的气泡起始温度越来越接近,表明气体高度饱和的系统中水分质量分数对气泡起始温度的影响很小。本文研究结果可为评估增容运行油浸式设备绝缘状态提供一定参考。Bubbles usually generate from the surface of the insulation paper of old and severely-wet transformers, which threatens the electrical insulation. Consequently, we prepared a model to simulate the structure of conductor insulation in transformer windings regarding the characteristics of moisture migration and temperature fluctuation, and set up an experimental platform. In the experiments, the rising rate of temperature, moisture content and gas saturation in the paper-oil system were varied to study the characteristics of bubble inception. The results show that certain temperature is the prerequisite for bubble formation. The bubble inception temperature decreases with the increase of temperature gradient, and the dispersity of bubble inception temperature is large at high temperature with relative slow grow. With further decrease in temperature rising rate, the bubbles can hardly be observed. During the temperature cycling, the inception temperature of bubbles increases. Bubble appears from the junction of adjacent paper layers at first and emerges directly on the paper surface during later cycles. Experimental observation reveals that bubbles evolved under different conditions can vary in morphology and location. Bubble inception temperature increases rapidly with the decrease of moisture content in the paper. Furthermore, moisture saturation in the system significantly influences the inception temperature. When the relative gas saturation increases from 5% to 25%, a decrease of 20 ℃ to 40 ℃ in bubble inception temperature arises. With further increase of moisture content in the system, the decreasing speed of bubble inception temperature slows down, and the difference between different moistened samples becomes closer, which shows that the moisture content in the system has little influence on the bubble inception temperature under highly gas-saturated conditions. The results can provide a reference for the evaluation of insulation state in oil immersed equipment during dynamic rating.

关 键 词：油浸式变压器 匝间纸绝缘 温度 气泡 含水量 溶解气体 

分 类 号：TM411[电气工程—电器]