多次雷电冲击电压作用下变压器油浸绝缘纸板累积效应特性

Accumulative Effect Characteristics of Transformer Oil Impregnated Paper Under Repeated Lightning Impulses

油纸绝缘是电力变压器最常用的一种绝缘介质,其在运行过程中不可避免的会受到多次雷电冲击电压的作用,在冲击电压的累积作用下变压器内绝缘有可能会产生不可逆的损伤。鉴于此,通过自动连续冲击电压发生器对油纸绝缘模型的累积施压,来模拟侵入变压器的雷电过电压对油浸绝缘纸板的累积效应。研究了雷电冲击电压幅值U与油浸绝缘纸板击穿时雷电冲击电压累积次数N之间的关系,即U-N特性。并采用Weibull模型分析了油浸绝缘纸板试品U-N特性的变化规律。还通过原子力显微镜(AFM)对比研究了不同次数雷电冲击电压作用后油浸绝缘纸板表面形貌的变化。研究结果表明:随着雷电冲击电压幅值的升高,油浸绝缘纸板累积直至击穿所需要的次数大幅度下降,雷电冲击电压对油浸绝缘纸板具有明显的累积效应;多次雷电冲击电压的累积作用会导致油浸绝缘纸板表面颜色与形貌的变化,200、400、600、800次标准雷电冲击电压作用后,油浸绝缘纸板表面粗糙度比累积试验前分别增加了0.61、2.80、5.97和11.76倍。

Oil-paper insulation, as a common insulation mode used in power transformers, is continuously and unavoid- ably subjected to repeated lightning impulses, which may cause irreversible damage to the insulation system. Therefore, by using a repetitive impulse accumulating test platform, we applied repeated lightning impulses to the oil paper insula- tion model to simulate the accumulative effect of transformer invading lightning impulse on the oil impregnated paper （OIP）. Then a systematic approach was carried out to obtain the U-N characteristics （the relationship between the ampli- tnde of lightning impulse and impulse number when OIP is broken down） of oil impregnated pressboard model under standard lightning impulse voltages. And the U-N characteristics were mathematically analyzed using a modified Weibull distribution model. The atomic force microscope （AFM） observation was carried out on OIP samples before/after the ac- cumulation of repeated lightning impulses. The results indicate that, with the increase in the amplitude of applied lightning impulses, the impulse number before breakdown occurring becomes increasingly smaller, which confirms the existence of accumulative effect. The roughness will increase by 0.61 times, 2.80 times, 5.97 times, and 11.76 times for OIP samples subjected to 200, 400, 600, 800 times of lightning impulses, respectively, compared with that of original OIP.