Abstract: Abstract: In order to take into account the thermal insulation effect of the L-shaped fire barrier in the cable tunnel and the convenience of construction and installation, it is necessary to determine the minimum height required for the L-shaped fire barrier under different working conditions. For this reason, this paper adopts FDS simulation method to numerically simulate the protective effect of the L-shaped fire barriers with different side plate heights on the cables of different voltage levels under different fire source powers, and analyze the temperature changes and smoke in the area where the partitions are installed. The results show that when the fire source power is 400 kW and 600 kW, the smoke spreading speed is about 50% and 66% faster than when the fire source power is 200 kW from the full combustion stage of the cable to the end of attenuation; When the 110 kV cable layer spacing is 0.5 m, with the fire source power of 200, 400, 600 kW, the optimal heights of the sides of the L-type fire barrier are 0.20, 0.25, and 0.25 m respectively; When the distance between the 10 kV cable layers is 0.25 m, the optimal heights of the sides of the L-shaped fire barrier under the three power of the fire source are 0.100, 0.125, and 0.125 m, respectively, and the temperature of the sheath layer of the protected cable above the partition is lower than the pyrolysis temperature. This research result can provide a reference for the height design of the side panel of the fire barrier under different working conditions.

Key words: Key words: cable tunnel fire, L-type fire barrier, side plate height, heat insulation effect, smoke diffusion