Safety Analysis On Signal Module Of The Full-electrical Computer Interlocking System

The railway signaling equipment or system must follow the principle of "failure-security", safety is the most critical to the railway signaling equipment. The higher reliability and safety of the railway signaling equipment are required with the increase in the railway signaling system function and the degree of complexity increases. Full-electrical computer system based interlocking is a safety-related system and its subsystem signal module is a safety-related equipment, safety integrity level of the safety-related equipment or system must reach to SIL4.The safety analysis and calculation of the signal module is closely linked with the interlocking system safety analysis, it has important meanings to ensure a safe operation of trains. In accordance with the relevant standard of the Ministry of Railways, the paper has finished the safety analysis and calculation of the execution unit signal module of full-electrical computer based interlocking which has been promoted to utilization. The safety analysis comprises two parts, the safety analysis of communicates with interlocking system and the signal module itself safety analysis.This paper first introduces the background and research status of the railway signaling equipment safety research, the structure and function of signal module is described in detail. Secondly, the paper introduces the communication mechanisms of signal module and interlock host, including the communication contents and the design of communication protocol. Besides, calculated the failure rate of each electrical components in communication circuit of signal module and computer interlocking system, built the reliability model for calculating its reliability based on the theory of reliability and safety analysis. Then calculated the hazard rate of message transmission, proved the safety communication procotol meets safety requirement.Lastly, references to the signal module circuit diagram of Lanzhou DaCheng Technology Co.,Ltd, the paper has completed the signal module itself safety analysis, mainly includes to take the home signal for example, the fault tree analysis is applied to establish the fault tree of signal upgrade display for qualitative analysis and quantitative calculation, then defined the important degree of relevant events, in addition, the hazard calculation reference formula is given and arrived at the tolerant hazard rate of signal module. The result can meet the safety integrity level SIL4of railway standard. The safety of entire computer interlocking system is determined by the safety of all safety related equipments, the signal module is a safety related equipment of system, therefore, the result which has been calculated from this paper focuses on the signal module safety analysis has important significance for the safety analysis and calculation of full-electrical computer interlocking system, as well as has a reference value in system design and operation maintenance in the future.