通过研究直流交联聚乙烯绝缘材料在雷电冲击电压和操作冲击电压下电树枝引发率与电压的变化关系,确定其起始电压U50%.在电树枝引发后,对针尖处进行了傅里叶红外光谱分析.结果表明:冲击电压下电树枝引发率对电压变化较为敏感,且标准操作冲击电压下的起始电压大于标准雷电冲击电压下的起始电压.电树枝引发后,可以看到针尖处交联聚乙烯大分子链中部分C-H键的断裂,并有少量C-O键和C=O键的生成.理论分析表明空间电荷是XLPE等聚合物电树枝引发的根本原因,对不均匀电场改善程度的不同导致两种冲击电压下电树枝起始电压差异的主要原因.
The relationship between voltage and the initiation rate of electrical tree in DC XLPE insulat-ing material under lightning impulse voltage and switching impulse voltage was studied, and then the initial voltage (U50%) of electrical tree was confirmed. After initiation of electrical tree, the XLPE samples around the pinpoint was analyzed via FTIR. The results show that the initiation rate of electrical tree under impulse voltage is sensitive to the variation of voltage, and the initial voltage of electrical tree under standard switching impulse voltage is higher than that under standard lightning impulse voltage. Some C-H bonds breaks, and a few C-O and C=O bonds generate in XLPE around the pinpoint after initiation of electrical tree. Theory analysis indicates that the space charge is the root cause of initiation of electrical tree. The different improving degree on the uneven electric field under two impulse voltages leads to the difference in initial voltage of electrical tree.
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