Significance of Defects Inside In-Service Aged Winding Insulations
Significance of Defects Inside In-Service Aged Winding Insulations
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DOI：
10.1109/tec.2006.888037
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发表时间：
2008-02
影响因子：
4.9
通讯作者：
C. Sumereder;T. Weiers
中科院分区：
文献类型：
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作者：
C. Sumereder;T. Weiers
这项研究旨在了解定子绕组绝缘局部缺陷的后果；因此，对在役老化发电机线棒进行了光学(微观)检查和耐压试验。在此背景下，研究了云母沥青绝缘的发电机线棒和云母环氧绝缘的发电机线棒。云母沥青绝缘在一台12千伏的水轮发电机上已经运行了43年。两台相同结构的10.5千伏发电机在服役35年和36年后，拆除了带有云母-环氧树脂绝缘的发电机线棒。从耐压试验中获得的击穿时间值使用威布尔分布进行了评估。除尺度参数外，该分布的威布尔指数还可用于早期失效的识别。对这些发电机的更换棒进行的耐压试验没有发现任何早期故障；然而，在两种类型的在役老化绝缘上都检测到了这种故障。特别是，在高水平的电应力和铜导体和接地墙绝缘之间的分层时，会出现这种情况。结果表明，对测量的击穿时间及其离散度的解释取决于电应力的大小。
This study aims to gain insight into the consequences of local defects in stator winding insulation; therefore, optical (microscopic) inspections and voltage-endurance tests have been carried out on in-service aged generator bars. In this context, generator bars with mica-bitumen insulations and generator bars with mica-epoxy insulations were investigated. The mica-bitumen insulations had been in service for 43 years in a 12 kV hydro-generator. The generator bars with mica-epoxy insulation had been dismantled from two identically constructed 10.5-kV generators after 35 and 36 years of service. The time to breakdown values obtained from the voltage-endurance tests were evaluated using a Weibull distribution. Apart from the scale parameter, Weibull exponent of this distribution allowed for the identification of early failures. The voltage-endurance tests carried out on replacement bars for these generators did not yield any early failures; such failures, however, were detected on both types of the in-service aged insulations. In particular, these occurred at high levels of electric stress and at delaminations between the copper conductor and the groundwall insulation. It is concluded that the interpretation of the measured time to breakdown values and their scatter depends on the level of electric stress.