穿管保护对ZR-VV电缆绝缘失效条件的影响

Effect of protecting with conduits on insulation failure of ZR-VV cable

采用自主设计的红外辐射加热炉对不同保护状态下的ZR-VV电缆受热时的绝缘失效条件进行研究。结果表明,保护方式和加热环境对ZR-VV电缆绝缘失效温度的影响甚微,其失效温度约为183.5(1±10.7%)℃;试样的绝缘失效时间随热通量的增大显著减小,穿管保护后,时间明显延长,变化规律采用指数函数能够很好拟合;当环境的热通量较低时,穿阻燃PVC管的保护效果略优于金属管;当热通量高时,后者优于前者。

The insulation failure conditions of ZR-VV cables under different kinds of protections were studied by means of the infrared radiation reheating furnace. The test data showed that ZR-VV cable insulation failure temperature was little influenced by different protections and thermal environment, which probably remained at 183.5（1±10.7%） ℃. Thus, the cable insulation failure time was decreasing with the increase of exposure heat flux and increased when the cable was under the protection of conduit evidently, and the related variation regularity could be well fitted with exponential function model. The protective effect of fire resistant PVC conduit was much better than metal conduit when it exposed to low heat flux, but just opposite when exposed to high heat flux.