基于弛豫过程的XLPE电缆绝缘老化状态评估

Ageing State Assessment of XLPE Cable Based on Relaxation Process

为了评估交联聚乙烯(XLPE)电缆的绝缘老化状态,引入了频率分布函数f (v)。首先采用极化-去极化电流法测得电缆弛豫电流,再用f (v)对弛豫电流进行拟合,得到能直观反映XLPE电缆老化状态的f (v)·v-log(v)曲线。结果表明:XLPE电缆弛豫电流在频域分布上有两个明显的峰,且随着老化程度的增加,两个峰的峰值和脉宽都增大。热老化电缆的弛豫电流在频域的峰值频率明显向低频方向偏移,而水树老化电缆却无明显偏移现象。f (v)对电缆的老化状态比较敏感,能反映XLPE电缆的绝缘老化状态。

In order to assess the insulation ageing state of crosslinked polyethylene(XLPE) cable, the frequency distribution function f(v) was introduced. Firstly, the relaxation current of cable was measured by polarization-depolarization current method. Then the relaxation current was fitted by f(v), and the f(v)·v-log(v) curves, which can reflect the ageing state of XLPE cable directly, was obtained. The results show that there are two obvious peaks in the frequency domain distribution of the relaxation current in XLPE cable, and with the increase of ageing degree, the amplitude and pulse width of the two peaks increase. The peak frequency of relaxation current in the thermal aged cable in frequency domain shifts to low frequency direction obviously, while there is no shifting phenomenon for the water-tree aged cable. The f(v) is sensitive to the ageing state of cable and can reflect the insulation ageing state of XLPE cable.