Design and research of suburban railway fire alarm system

With the rapid development of suburban rail transit, fire safety issues have received more and more attention. As the first line of the Shanghai Suburban Railway, the fire safety problem of the Shanghai Suburban Railway Airport Link Line is more prominent. In this paper, an automatic fire alarm system is designed and researched for the fire safety problem of the Shanghai Railway Airport Liaison Line, which adopts a hierarchical distributed structure and can realize accurate fire detection thorough immediately sending fire alarm information to the station control room and line operation control center and informing the location of the fire area. At the same time, the system also coordinates with the BAS system and ISCS system or independently realizes the linkage control of fire fighting equipment. The research results of this paper are of great significance for improving the fire safety level of Shanghai railway airport links.


Introduction
The Suburban railway FAS system adopts three levels of control mode: central, station, and site.The FAS system also has fire detection, alarm, linkage control, and other functions.The FAS system must have high reliability, so scholars try to adopt the FAS separate networking method, and the integrated monitoring system does not integrate FAS but only link with FAS to ensure the stability of the FAS system [1].At the same time, the FAS system must ensure that it can detect and issue an alarm signal in time in the event of a fire.At the same time, the location information is sent to the integrated monitoring system, and the integrated monitoring system also enters the fire mode, links with the BAS system, and takes a series of measures to respond to the fire [2].The suburban railway fire alarm system should have a simple and easy-to-use operation interface to facilitate the operation and management of maintenance personnel.For the principle of automatic fire alarm authority control, the control authority (mode) of the automatic fire alarm system should follow the basic principle that manual control is higher than automatic control and local control is higher than remote control.When the operation is manual, all automatic trigger commands will fail [3]; When it is automatic control, it should be divided into the priority of central and station-level operation according to the characteristics of the controlled equipment.FAS system software has a sound identity authentication mechanism [4] and can set multi-level, group operation authority, different levels, different groups of operation authority to set different passwords.The general operation does not require passwords but needs to confirm fire extinguishing and other higher levels of passwords [5].

Fire alarm system scheme selection and composition
2.1 Integration and interconnection scheme with integrated monitoring system Scheme one: The FAS system is interconnected with the integrated monitoring system, and the optical fiber provided by the communication system is used to form a full-line FAS-independent optical fiber ring network, to realize the interconnection between the fire alarm controllers of the entire FAS line and the central FAS workstation and the FAS maintenance workstation, and complete the monitoring and maintenance functions of the entire FAS line [6].The network can ensure that the full-line monitoring function of FAS is not affected when the integrated monitoring system redundantly monitors network failures, and the FAS system is relatively independent.FAS is equipped with a fire alarm host in the fire control room of each station.The network diagram of the whole line system of the interconnection solution is shown in Figure 1.Scheme two: FAS system is integrated into the integrated monitoring system.FAS is not separately networked, using the ISCS transmission network as its full-line information transmission channel.Through the gateway to provide two Ethernet interfaces, the FAS fire alarm controller is directly connected to the switch of the integrated monitoring system.The use of ISCS full line redundant backbone network is its full line information transmission channel, to meet the reliability requirements of FAS.The integrated monitoring system uses the VLAN function of its switching equipment to divide logically separate virtual network channels for FAS.ISCS sets up workstations at each station to implement the station-level functions of FAS.In the control center, the integrated monitoring system sets up the operator workstation to complete the FAS central-level function and realizes the integration of the FAS central level in the integrated monitoring system.The network diagram of the whole line system of the integration solution is shown in Figure 2.  Scheme selection: The network communication capability, scalability, reliability, and other performance of the above two schemes are comparable, and both can meet the functional requirements of the fire alarm system.Due to the separate configuration of the entire optical fiber ring network and workstation, the FAS independence of Scheme 1 is higher than that of Scheme 2, which can ensure that the function of FAS is not affected in the event of a network failure of the integrated monitoring system.Therefore, it is recommended to design an integrated monitoring system (ISCS) and an interconnected fire alarm system (FAS).

Central-level system composition
In this route, the FAS system is interconnected with the integrated monitoring system, and its central configuration is configured by the FAS system itself.

Station-level system composition
Fire alarm controller through sensors (such as smoke/temperature detector), manual alarm button, monitoring module, and control module, monitoring equipment system.The station fire alarm device is connected to the central control center of the FAS system through the dedicated transmission network of the FAS system and is interconnected with the integrated monitoring system through the RJ45 Ethernet data interface to better realize the linkage operation.The interface between the ISCS system and the FAS system is designed as shown in Figure 3.The station-level FAS system is the core equipment of station-level FAS, which has the function of independent operation from the line system network and is equipped with an emergency power supply device.Data exchange between station FAS and BAS is possible via the RS485 interface [7].The FAS and BAS interface design is shown in Figure 4.

Composition of fire linkage control system
The Suburban railway fire linkage control system mainly includes a fire alarm system, integrated monitoring system, and environment and equipment monitoring system.The linkage equipment includes an alarm bell, broadcasting system, PIS, CCTV, AFC turnstile, access control door lock, elevator, escalator, ventilation and air conditioning system, fire water supply equipment, screen door, emergency lighting, non-fire power supply, etc.In rail transit operation, the reasonable and effective linkage of these systems is the key to ensuring the rapid and reliable disaster prevention and relief system of the suburban railway [8].

Control mode of the fire linkage system
According to the execution mode of linkage, the fire linkage system is divided into the following three categories.

Fully automatic linkage
When the relevant trigger conditions of the predefined linkage plan are met, ISCS automatically sends relevant control commands to the interface system that needs to be linked, without personnel intervention.

Semi-automatic linkage
When the relevant trigger conditions of the predefined linkage plan are met, ISCS issues an alarm linkage message on the workstation HMI to prompt the operator, and after the operator confirms the execution, ISCS automatically issues control instructions to the system that needs to be linked.

Manual linkage
You can use manual linkage to execute the configured linkage plan, regardless of whether the linkage plan is configured with trigger conditions or whether the trigger conditions are met.

Research on fire linkage scheme
When the fire is confirmed, the FAS system starts the alarm bell, anti-smoke fan, strong start emergency lighting, cuts the fire power supply, opens the AFC system turnstile, access control, stops the escalator operation, and requires the fire hydrant pump to be started through the control module [9].
The FAS system directly issues fire mode commands to the BAS system, and the BAS system automatically starts the corresponding mode, thereby controlling ventilation and smoke exhaust and equipment entering the disaster relief state, stopping the operation of the descending escalator, and making the guide sign enter the fire mode.The FAS system simultaneously sends pattern instructions to the integrated monitoring system.After receiving the mode instruction, the integrated monitoring system changes from normal operation mode to fire operation mode, transfers the broadcast and PIS to the fire emergency state, monitors the status of the equipment, and coordinates the subsystems such as driving command, disaster prevention and safety according to the on-site alarm information, train location, and other relevant information, so that it is in the fire relief mode, providing reliable guarantee for disaster prevention, rescue and accident handling.To ensure safety, the integrated backup control panel (IBP) is uniformly set up in the control room of each station, and when the mode control fails, the relevant emergency operations can be directly carried out through the IBP, including the emergency control of the environmental control ventilation and smoke exhaust system and the fire linkage control; Door lock unlock control of the gate and access control of the automatic ticket vending system; Opening of the screen door; Escalator control [10].

Conclusion
Combined with the project of Shanghai Railway Airport Connection Line, this paper designs a fire alarm device for the municipal railway, analyzes the advantages and disadvantages of the integration or interconnection scheme of the automatic fire alarm device system and the integrated monitoring system, adopts the scheme of the interconnection of the automatic fire alarm device system and the integrated monitoring system, then explains the composition of the automatic fire alarm device system from the central level and the station level, and puts forward the fire linkage scheme between the various systems in the fire mode, to effectively reduce the impact of the disaster and ensure the normal operation of the suburban railway and the safety of passengers.

Figure 1 .
Figure 1.Network diagram of the whole line system of the interconnection solution Integrated monit oring systemat the central l evel ISCS station-level workstations

Figure 2 .
Figure 2. Integrated solution full line system network diagram

Figure 3 .Figure 4 .
Figure 3. Interface design between ISCS system and FAS system