直流电压下油纸绝缘杂质小桥的形成过程  

Generation Process of Impurity Bridges in Oil-paper Insulation Under DC Voltage

作　　者：李金忠[1,2] 张乔根[1] 李原[1] 王同磊 倪鹤立 

机构地区：[1]西安交通大学电气工程学院,西安710049 [2]中国电力科学研究院,北京100192

出　　处：《高电压技术》2016年第12期3901-3908,共8页High Voltage Engineering

基　　金：国家电网公司科技项目(GY71-14-027)~~

摘　　要：换流变压器阀侧绕组在运行中需同时承受交流、直流电压作用,直流电压下油中固态杂质对油纸绝缘性能具有极大威胁,但一直缺乏固态杂质形成与发展机理的研究。为此,设计了油纸绝缘模型,分析了直流电压下杂质小桥的成分及产生原因,并在此基础上研究了恒定负极性直流电压作用下杂质小桥的产生、发展过程,同步获得了该过程对应的局部放电特征。研究结果表明:杂质小桥由直流电场作用下绝缘纸表面脱落的纤维丝束构成。小桥产生、生长乃至引起绝缘击穿的过程可分为3个阶段,在此过程中杂质小桥数量明显增加,小桥直径由第1阶段的100μm增长至第3阶段的1 mm,对应局部放电平均放电量由400 p C增加到1 000 p C,每分钟放电次数由几十次上升为上百次。其中,第3阶段产生的"高危小桥"是引起绝缘破坏的关键因素,最终击穿即沿"高危小桥"发生。此外,实验中后期出现了"集群放电"现象,该过程是由杂质小桥的产生、消失现象造成。The valve-,;ide windings of converter transformers have to endure combined AC-DC voltage in operation. Under DC voltage, solid impurities generated due to PD （partial discharge） may cause great threat to the insulating ability of oil-paper insulation. However, the generation and growth mechanism of solid impurities is still unavailable. In this pa- per, an oil-paper insulation model was established and the content of micro impurity bridges was analyzed. The generation and growth process of micro impurity bridges under negative DC voltage were investigated. Besides, PD characteristics during the above process were also acquired synchronously. The experimental results show that micro bridge impurities are formed by fiber btmdles detached from the surface of the insulating paper under DC electric field. The generation and growth process of micro impurity bridges can be divided into three stages. Among the stages the quantity of micro bridges increases significantly. The diameter of the bridge increases from 100 μm in the first stage to 1 mm in the third stage, along with which is the increase of the PD average charge from 400 pC to 1 000 pC and the PDs rates from dozens to hundreds per minute. At the third stage a ＇hazardous bridge＇ emerges, leading to the final breakdown of the insulation. Besides, a ＇cluster discharging＇ phenomenon appears in the second stage, which is associated with the generation and the disappearance of micro bridge impurities.

关 键 词：直流电压 换流变压器 油纸绝缘 局部放电 纤维分子 杂质小桥 集群放电 

分 类 号：TM855[电气工程—高电压与绝缘技术]