Fire accidents in power cable tunnels have become an important issue that threatens the safety of urban power grids. In order to explore the mechanism of power cable tunnel fires

this paper introduced a dynamic simulation method of tunnel fires caused by power cable electrical faults. Firstly

a mathematical model of single-phase arc grounding fault based on the experimental results of the internal arc fault of the cable was established. Secondly

the fire source model consisted of the average power of the single-phase arc grounding fault and the heat release rate per unite area of the cable combustion was built. Finally

a typical cable tunnel was taken as an example to conduct fire dynamic simulation and fire risk assessment. The simulation results show that the cable is ignited after the arc fault occurs for 14.4 s. The cables laid within 50 cm from the same side of the faulty cable were at high risks; cables laid within 50～75 cm from the same side of the faulty cable are at medium risks; and other cables in the tunnel are at low risks. The research results can provide theoretical support for fire prevention and safe maintenance of cable tunnels.