矿山电力变压器油纸绝缘老化的微观结构及放电特性研究*

文章对比分析了实际寿命周期中矿山电力变压器(矿山变)与普通电力变压器(普通变)油纸绝缘老化的微观结构及放电性能。利用粘度测试仪、光学显微镜及扫描电镜等现代测试手段,并根据放电相位分布(phase-resolved partial discharge,PRPD)模式,分析了油纸的聚合度、表面形态及微观形貌,以及放电起始电压、放电量及放电次数等。结果表明：温度、水分和生成物的协同作用导致了老化过程中油纸微观结构缺陷形成并进而引发电树枝,绝缘缺陷的分散性导致了放电相位分布中的“波浪”特征;运行过程中,矿山变油纸老化更加严重,局部放电现象更加激烈;矿区运行环境是造成矿山变油纸老化更严重的主要原因,矿山变油纸微观结构变化更加明显是导致其放电特征变化更加显著的直接原因;对矿山变绝缘状态的监测须从严执行电力标准,局部放电能更有效进行矿山变绝缘状态诊断。

Study on microstructures and discharge characteristics of aged oil-paper insulation in mine power transformer

This paper compared and analyzed microstructures and discharge characteristics of aged oil-paper insulation in mine power transformer and ordinary power transformer in actual life cycle. By means of modern testing methods such as viscosity tester, optical microscope and scanning electron microscope (SEM), and according to phase-resolved partial discharge pattern (PRPD), polymerization degree, surface forms, micromorphology of oil-paper insulation, as well as its discharge inception voltages, discharge levels and discharge numbers, are analyzed. The results reveal that: synergistic effects of temperature, moisture and products lead to formation of oil-paper microstructure defects during aging, which in turn triggers electrical tree branches, and dispersion of insulation defects leads to "wave" characteristics in discharge phase distribution; in the process of operation, aging of mine transformer oil-paper insulation becomes more serious, its partial discharge (PD) phenomenon becomes more intense; operating environment of mining area is main reason for more serious aging of mine power transformer oil-paper insulation, meanwhile changes of microstructure defects in mine power transformer oil-paper insulation is more obvious, which is direct cause for more significant changes of its discharge characteristics; electrical power standards should be more strictly implement for monitoring of mine power transformer insulation state, and partial discharge can more effectively diagnose mine transformer insulation state.