湿热环境下变压器套管绝缘特性劣化及机理分析

Analysis of Degradation and Mechanism of Insulating Characteristics of Transformer Bushings in Humid Environments

为研究湿热环境下变压器套管绝缘特性的劣化及机理,针对在湿热环境中长期运行已产生缺陷的油纸绝缘套管,进行了不同温度和电压下高压介损、电容和频域介电谱(FDS)试验。对缺陷套管解剖采样,测试纸样含水率和聚合度,分析套管受潮老化过程。结果表明:高压介损、电容和FDS试验能够显著反映套管内部存在的受潮老化缺陷。与正常套管相比,缺陷套管高压介损和电容与外施电压和温度均具有较强的相关性,FDS中在整个频段内增大,曲线形状改变,电容数值变大。套管受潮部位主要是导杆头部密封圈以及末屏,大部分水分被绝缘纸吸收,高水分区域集中在电容芯子下端和最内层,水分与外界高温共同作用下,绝缘纸加速老化,产生放电。该研究为湿热环境下套管优化设计与运行维护提供参考。

To investigate the degradation and mechanism of insulating characteristics of transformer bushings under hot and humid conditions,high voltage dielectric loss,capacitance,and Frequency Domain Spectroscopy(FDS) tests were performed on oil-paper insulated bushings that had developed defects after long-term operation in such environments,at various temperatures and voltages.The defective bushings were dissected for sampling,and the water content and degree of polymerization of the paper samples were tested to analyze the bushings' moisture-induced aging process.The results showed that high voltage dielectric loss,capacitance,and FDS tests could significantly reflect the presence of moisture-induced aging defects inside the bushings.Compared to normal bushings,the defective bushings demonstrated a stronger correlation between high voltage dielectric loss,capacitance and the applied voltage and temperature,with an increase in tanδ across the entire frequency range in FDS,a change in the curve shape,and an increase in capacitance values.The main moisture-affected parts of the bushing were the sealing ring at the head of the conductor rod and the end screen,with most of the moisture being absorbed by the insulating paper.Areas with high moisture content were concentrated at the lower end of the capacitor core and the innermost layer.Under the combined effects of moisture and external high temperature,the insulating paper aged more rapidly,leading to discharges.This study provides a reference for the optimized design and operational maintenance of bushings in hot and humid environments.