电缆开裂原因分析

The Analysis of Cable＇s Cracking

岭澳核电站主控室照明用电缆（核级K3类），运行不到3年，伸入灯管段的电缆芯线绝缘发生变色脆化开裂现象，而其它低压动力电缆未发现有该异常现象。为了验证现场所用类似电缆的整体可靠性，项目组对4种不同电缆的样品进行了性能测试，并对该电缆芯线绝缘的开裂机理进行了分析。分析认为：在光、热、氧、应力的共同作用下，该照明电缆芯线绝缘发生了变色及脆性开裂，绝缘材料的耐光性较差。建议的纠正行动是：一方面，目前应改变主控室照明电缆在灯光侧的接线方式，芯线不能直接裸露在灯光下；另一方面，在电缆有可能受到灯光照射或类似环境时，电缆护套及绝缘材料设计应有耐光性的要求。

The lighting cable （belongings to equipment safety class IE and category K3）, which is used in main control room（MCS） of LingAo Nuclear Power S＇tation（LANPS）,has worked nearly three years. It is found that the three cores insulation wall of this lighting cable turned colors and cracking appeared inside the lighting tube, which directly and closely exposes to the lighting radiation. However, the similar phenomena on other low power /lighting cables have not been found yet in site. In order to verify the reliability of the low power cables including lighting cable in station, we have checked and analyzed the properties of 4 kinds of cable samples namely 1 cracked lighting cable and 3 other low power cable/lighting cable samples. The examination shows that the color changing and cracking for insulation wall is resulted from co-effect of light, heat, oxygen and stress, and the resistance of light for insulating materials is poor. Suggestions include that the cormection method of the lighting cables on the lighting side should be changed to prevent the core from directly exposing to the light in the main control room. On the other hand, when cables are exposed to light or similarities, sheath and insulation materials of the cables should be able to resist light.