The Law of Insulation Failure of ZR-VV Cables under the Circumstances of Different Thermal Environments

The law of insulation failure of PVC insulated PVC sheathed flame retardant cable (ZR-VV) under the circumstances of three different protection modes and six different thermal radiation fluxes is discussed in this paper. The indigenous designed SDR-1 thermal radiation test furnace for plastic cables is used to simulate different thermal environments, in which the thermal radiation fluxes are 3 kW/m2、5 kW/m2、7 kW/m2、24 kW/m2、40 kW/m2、56 kW/m2 respectively and the three different protection modes are directly exposed, protected by metal tube and protected by flame retardant PVC tube. From the results of the experiments, the followings can be concluded: The insulation failure time and the thermal radiation flux of ZR-VV cables have exponential relations under a particular protection mode. The insulation failure time gets longer obviously when it is protected by tube than exposed directly. On the whole, the flame retardant PVC tube protects better than the metal tube in low thermal radiation flux. However, both two have similar protection effects when the thermal radiation flux is high. The insulation failure temperature of this kind of cables is about (183.5±10.7%)°C.