Research On Reliability And Safety Of CTCS-3

A large number of complex electronic related components and computer systems areapplied in Chinese Train Control System level3(CTCS-3) that features large-scale, redundantconfiguration and complex structures. CTCS-3must have high reliability and high security asit is the core signal technology and equipment to ensure safe, reliable and efficient operationof speed of300~350km/h trains. However, it is often difficult to avoid the occurrence of thefault. Although the dangerous sides fault are considered as small probability events, theconsequences are disastrous. Therefore, the research on reliability and safety of CTCS-3isextremely important for the protection of high-speed trains.The in-depth analysis of the structure and function of CTCS-3was conducted as thebasis for the reliability and safety analysis of CTCS-3, combined with the failure data of traincontrol system equipment. From the perspective of systems engineering, fault treeanalysis(FTA) and Bayesian network(BN) technology were used to analyze and evaluatesystematically the reliability of CTCS-3, considering the failure mode feature ofmaintainability, common cause failure, polymorphism and other factors. The potential risks oftrain control system were identified, as well the cause and possible consequences of theserisks. The security risk of train control system was assessed by the risk assessment modelbased on BN. The main contents of this paper are as follows(1) The structures of on-board equipment and ground equipment of CTCS-3weredissectted, as well its core functionality and functional hierarchical. According to theequipment fault emergency treatment cases of train control system, the equipment failure dataof train control system were analyzed and summarized at the aspects of occurrence, symptomsand causes, solving approaches and impact on train.(2) Many complex faults occurred in operation process of train control sytem. Takinginto account to the failure mode of train control system behaving maintenance, common causefailure, polymorphism and other features, the reliability of CTCS-3was analyzed andevaluated. Firstly, starting from the perspective of availability, the reliability model ofvehicle-mounted subsystem was established using FTA and BN to analyze its availability.Secondly, according to the conceptual fault tree of CTCS-3, the reliability of CTCS-3wasanalyzed and evaluated by the two states reliability model of CTCS-3based on BN. Finally,the degradation scene of CTCS-3train control system was acted as a particular way ofworking, the three states Bayesian network reliability modeling of normal operation, degradedoperation and system failures was built, and the reliability of CTCS-3consideringdowngrading case scenario was analyzed and evaluated. (3) In accordance with identifying the potential hazards, likelihood and consequences ofthe risk of accidents, a security risk assessment methodology based on BN was established.On the basis of accident/failure databases of rail signaling system, and using the riskassessment model based on BN, tolerable hazard rate(THR) of accident leaded by the riskswas calculated to estimate whether the system can meet the safety requirements and achievesecurity objectives. So as to some assistance and specific implementation methods wereprovide to scientifically assess the safety of CTCS-3.