利用局部放电相位分布分析油浸绝缘纸损伤

Analysis of Damage on Oil-impregnated Insulation Paper Using Phase Distribution of Partial Discharge

为深入了解油浸绝缘纸损伤过程中局放统计特性的变化及其与材料损伤的关系,对局部放电二维图谱、放电统计特征量及表面损伤状况利用油浸纸内扁平气隙模型进行了试验研究。根据局部放电二维图谱的变化将损伤过程分为5个阶段,分析了5个损伤阶段中放电统计特征量的变化,并分别用显微镜和扫描电镜对绝缘的表面情况进行了分析,并提供了判断油浸绝缘纸表面状况的参考信息。研究结果表明:在5个损伤阶段中,二维图谱的不对称度和相关度逐渐稳定在1附近,放电量偏斜度在绝缘击穿前呈现负值;绝缘表面伴随有"液滴"和"晶状固体"相继生成;"液滴"的生成是不对称度和相关度趋于稳定及周期性"簇"状出现的原因,"晶状固体"畸变电场结构、影响放电的发生发展,是导致"凹坑"生成并引发"电树枝"的原因。

Two-dimensional phase distribution of partial discharge（PD）,statistical features of two-dimensional phase distribution,and surface damaging conditions on oil-impregnated insulation paper were studied during the damage process caused by PD within the cavity of the paper.According to two-dimensional phase distribution of PD,the damage process can be divided into five stages,and the variation law of statistical features was analyzed during the damaging process.At each of the stages,surface damaging conditions of insulation were analyzed by optical microscopy and scanning electron microscopy.Results reveal that,during the five damaging stages,asymmetry（Asy）and cross-correlation factor（Cc）of two-dimensional phase distribution gradually stabilize near the constant 1,and skewness（Sk）of two-dimensional phase distribution for discharge amount presents as negative value before incoming breakdown of insulation paper.Meanwhile,droplets and crystalline solids are generated in sequence.Droplets make Asyand Ccgradually stabilized,and cause periodical＂cluster-like＂featured.Crystalline solids generated on the insulation surface distort the electric field,which is an important cause for＂pitting＂and＂electrical treeing＂on insulation surface.Reference information for the assessment of surface conditions of oil-impregnated insulation paper is provided.