Purpose/Aim
The power cable tunnel fire has seriously affected the safety of the power system and has become an important issue threatening the safety of the urban power grid. At the same time, with the fire spread, it produces a large amount of high-temperature toxic and harmful gases, these gases threat safety of on-site operation and maintenance personnel and rescuers seriously. Therefore, it is very important to study more effective fire extinguishing methods for power cable tunnels. In recent years, high-pressure water mist fire extinguishing system has been more and more widely used because of its good cooling, smoke removal and fire extinguishing performance. The suppression effect of high-pressure water mist on fire spread in cable channel was studied by this paper.
Experimental/Modeling methods
The length of the fire protection area is set at 50m, and the tunnel size is 1.5m wide and 1.9m high. In the test site, three 400mm² cables and combustion-supporting materials are set in the upper, middle and lower layers of the cable support on the same side. This study establishes a cable tunnel model with a size of 1.5m×1.9m×50m, and sets up three 400mm² cables in the upper, middle and lower layers of the cable support on the same side. By setting different working conditions of fire source position, number of nozzles, average particle size and nozzle pressure, the influence of cooling performance and particle size of high-pressure water mist on cooling effect was studied.
Results/discussion
The research results show that, influenced by the structure and wall of the underground pipe gallery, the combustible forms unilateral combustion and flashover during combustion. With the high-pressure water mist nozzle turned on, the flashover times are reduced, the temperature in the power Cable tunnels is obviously reduced, and the combustion time is shortened. The droplet size has a major influence on the cooling and fire extinguishing performance of high-pressure water mist, and the particle size of 100 μm is the most efficient.
 

Water mist,Fire suppression,Large scale,Thermal transient,Power cable tunnel