热历史过程对XLPE电缆热历史温度的影响研究

文中采用差式量热扫描(DSC)法对实际服役的交联聚乙烯(XLPE)电缆绝缘的热历史过程进行研究,发现不同XLPE试样的DSC一次升温曲线存在着明显差异,具体表现为不同试样热历史峰的位置、大小及形状存在着较大差异,甚至有些试样观察不到热历史峰。为了研究上述差异产生的原因,对不同温度不同热老化时间的XLPE试样进行了DSC测试,当XLPE电缆绝缘所经历的热历史温度高于熔融温度时,DSC一次升温曲线上不会有热历史峰出现,此时DSC曲线的变化主要由热氧降解对XLPE晶体结构的破坏所引发。当XLPE电缆绝缘所经历的热历史温度低于熔融温度时,在DSC一次升温曲线上就会观察到热历史峰,XLPE电缆绝缘处于该热历史温度的时间越长,则热历史峰的面积越大,热历史峰的峰值温度越高,甚至有可能高于实际的热历史温度。

Influence of thermal history process on the thermal history temperature of XLPE cable

Differential Scanning Calorimeter (DSC) was used to test the thermal history temperature of the insulation of XLPE cables in service. It was found that there were significant differences in the DSC 1st heating curves of different XLPE samples. On the most of the DSC curve of XLPE samples, thermal history peaks were found, and there were differences in the position, size and shape of these peaks. However, no thermal history peak could be observed on the DSC curve of the other samples. In order to investigate the reasons for the above differences, we performed DSC tests on XLPE samples at different temperatures for different temperatures. It was found that when the thermal history temperature experienced by XLPE cable insulation is higher than the crystal melting temperature of XLPE, there is no thermal history peak on the DSC primary heating curve.At this time, the change of DSC curre is mainly caused by the destruction of XLPE crystal structure by thermal sxygen degradation. When the thermal history temperature experienced by XLPE cable insulation is lower than the crystal melting temperature of XLPE, a thermal history peak can be observed on the DSC primary heating curve. The longer the XLPE cable insulation is at this thermal history temperature, the larger the area of the thermal history peak and the higher the peak temperature of the thermal history peak, and may even be higher than the actual thermal history temperature.