Abstract:Due to the narrow and elongated space of urban underground cable, preventing fires in power cable tunnels is of great importance for ensuring the safety of urban power grids. In response to the scenario where a cable fault in a mixed-laying configuration within the same trench leads to a fire and triggers grid failure, fire dynamics simulation tools are employed to investigate the dynamic evolution characteristics of fires caused by the combustion of heat sources within the cable insulation layer in the constrained space of cable tunnels. The results has important practical significance for preventing fires in cable tunnels, controlling fire spread and protecting the safety of people's lives and property.