Abstract: In order to study the ignition process of the urban underground pipe gallery cable under the internal heat source, the ignition process of the 110 kV high voltage cable was analyzed by using the 3D heat transfer and pyrolysis model of FDS. The cable ignition process under different heat source types was studied, and the temperature distribution under different working conditions was analyzed. The influence of heat conduction by different cable core materials on cable ignition process was analyzed. The results showed that the cable has little fire risk under normal operation and short- term overload, but long- term overload and joint failure will greatly increase the fire risk of the cable. Different from the direct ignition process of external flame, the ignition of cable by internal heat source requires a considerable period of time for heat conduction and pyrolysis. Under the same conditions, the HRR peak and the flame spread velocity of aluminum core cables is greater than that of copper core cables.The good thermal conductivity of the cable core material can significantly increase the cable ignition time and reduce the risk of fire. A cable combustion driving mode suitable for internal heat sources is proposed.As time progresses, the cable combustion process transitions gradually from the initial internal heat source driving phase to the internal heat source and flame driving phase.

Key words: cable fire, ignition process, numerical simulation, drive mode