Setting and laying of temperature sensing optical fibers for tunnel cables

Factors to consider in equipment layout. Vibration caused by driving in the tunnel; Electromagnetic interference caused by locomotive start and stop; The humid environment inside the tunnel; Rats inside the tunnel may bite equipment and cause damage; Other interferences that affect system operation.

Layout of temperature sensing fiber optic controller. The temperature sensing fiber optic controller is installed in the station control room or comprehensive monitoring equipment room.

Layout of temperature sensing optical cables in interval tunnels. The heat sources for sensing environmental temperature through temperature sensing optical fibers include radiative heat and convective heat. Convective heat mainly relies on the accumulation of hot air at the top of the tunnel for propagation, while radiative heat basically propagates in a straight line. According to experimental data analysis, when a fire occurs in a tunnel, the influence of radiation heat and convection heat on temperature sensing fiber optic temperature detection is basically equivalent. At the same time, as analyzed above, convection heat propagation can only be effectively detected when the fire inside the carriage is large. Therefore, radiation heat should be considered as the main factor for fire detection in carriages. So temperature sensing optical cables should be installed at high places such as the inner wall of the tunnel and train windows. In this way, if a fire occurs inside the carriage, the temperature sensing optical fibers can sense the radiation heat through the windows, providing early warning of the fire.

Practical applications have proven that temperature sensing fiber optic systems, with their good feasibility and cost-effectiveness, are a powerful supplement to traditional tunnel fire alarm systems. At the same time, other extended applications of temperature sensing fiber optic systems are also constantly expanding and attracting attention in their use.

Real time monitoring of temperature field inside underground tunnels. Under normal circumstances, the system can also serve as an interval temperature detector for BAS, monitoring the temperature of the tunnel environment, and energy-saving control of the tunnel ventilation system; When the train is blocked, the blocking mode can be controlled based on the actual situation inside the tunnel.

Protection of interval ring network cables. The system can monitor the heating situation of the interval ring network cables (mainly monitoring the heating situation of cable joints) in real time, and can promptly alert and handle abnormal temperature of cable joints to ensure the normal operation of the system.

Fire alarm in the area under the platform board and cable interlayer. At present, most rail transit substations that do not use temperature sensing fiber optic systems mostly use temperature sensing cable detection systems under the cable interlayer, which have been criticized by many operating departments due to their high level of misoperation and inconvenience in maintenance. At the same time, under the platform board without corresponding fire alarm equipment, there are many cables and other high safety hazards. If a temperature sensing fiber optic system is installed in the interval at this time, temperature sensing fiber optic cables can be installed in areas that are not suitable for maintenance, such as the cable interlayer and platform board, during the arrangement of fiber optic cables, which can solve all the above problems. As a relatively emerging fire detection method, temperature sensing fiber optic systems can be predicted to have increasingly wide applications in the rail transit industry.