Abstract: In response to the problem of insulation failure, signal distortion, and even interruption in the control circuit of exposed fire-fighting equipment under the threat of high temperature in fire, this paper selects NH-KVV-3×2.5 cable commonly used in fire-fighting equipment control circuit as the research object. Through cable fire resistance test and ANSYS simulation, the influence of different thicknesses of fireproof coating applied to metal pipes on the temperature field distribution and insulation failure time of internal cables is studied. The experimental results show that different thicknesses of fireproof coatings have a significant protective effect on cables under fire conditions, delaying the rate of cable temperature rise significantly. However, due to the characteristics of the intumescent fireproof coating itself, excessive coating thickness can lead to a decrease in expansion ratio and a reduction in the amplification of cable insulation failure time. The optimal thickness range for fireproof coatings is 1.5~2.0 mm. The insulation failure temperature of the cable is not affected by the thickness of the fireproof coating, and is basically stable at about 148.7 ℃. The ANSYS simulation results show that as the thickness of the fireproof coating increases, the temperature distribution cloud map of the cable shows that the outermost temperature of the fireproof coating remains basically unchanged, and the temperature in the internal area decreases at the same time during the simulation period. The temperature variation law of the insulation layer obtained from the experiment and simulation agrees well, and the maximum relative error between the function of the outer surface temperature-combustion time-fireproof coating thickness of the wire insulation layer constructed based on simulation and the fitting curve of the experimental data remains within 18.1%, proving that the model has high reliability.

Key words: NH-KVV cable, insulation failure, failure temperature, failure time, ANSYS simulation