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为了深入了解发电机绕组绝缘老化机理,对运行老化的绕组绝缘系统进行了评估。于是,将一台8kV过电压试验失效的水轮发电机的线棒拔出。先前,由于该电机曾用蒸汽清洗,故假定绕组绝缘已吸收水份。按此假设,在0.2U_N下测得功耗因数为9.6%。为研究该发现结果,对电压耐受试验进行了测试:运行老化绝缘的时间-击穿值与未老化更换线棒比较减小了27倍。所以,运行老化绝缘吸水可显著缩短绝缘剩余寿命。除主绝缘外,来自发电机轴承的油已部分地溶解绕组电晕防护层。从而使电晕防护层的最大表面电阻值比它原来的值大10倍。这样在定子槽中可能产生放电,影响可靠运行。因此,对有类似问题的绕组进行这种形式的放电检查。
In order to understand the insulation aging mechanism of generator windings, the aging winding insulation system was evaluated. As a result, a 8kV over-voltage test failure of the hydro-generator pull out the bar. Previously, since the motor had been steam-purged, it was assumed that the winding insulation had absorbed moisture. Based on this assumption, the power factor measured at 0.2U_N is 9.6%. To examine the findings, the voltage withstand test was tested: the time-to-breakdown value of operating burn-in insulation was reduced by 27 times compared to unaged cable replacement. Therefore, the operation of aging insulation water absorption can significantly shorten the remaining insulation life. In addition to the main insulation, the oil from the generator bearings has partially dissolved the winding corona barrier. As a result, the maximum surface resistance of the corona barrier is 10 times greater than its original value. This may cause discharge in the stator slots, affecting reliable operation. Therefore, this form of discharge inspection is performed on windings with similar problems.