Research On The Safety Risk Assessment For The Balise System Of CTCS-2

As the main information transmission system of Chinese train control system at level 2(CTCS-2),the balise system plays an important role in ensuring the safety operation of trains.However,in the real application,the balise system may meet malfunctions frequently such as massage exception,balise transmission module(BTM)failure and receiving the acquiescent massage from lineside electronic unit(LEU),which can seriously influence the operation efficiency and even the operation safety.In this case,it is impossible to satisfy the safety demands for relying on the traditional rules to ensure the safety operation of balise system.In order to improve the security of balise system and generate a scientific management,the corresponding functions,state transitions and information interaction were selected as the research objects to generate the risk assessment with risk assessment theory.Firstly,under the analysis of the function demands and operation principles of balise system,the combination model of the system was constructed.Through hazard and operability analysis(HAZOP)method to generate the risk identification,the failure modes of the system can be obtained to analyze the failure causes as well as the effects.Thus,the corresponding risk identification table for each model of balise system can be designed.The risk identification results showed that the combinational risk identification method of system model and HAZOP can comprehensively identify the failure modes of the system.Secondly,according to the division standard of risk level and the actual situation,the experts can score on the relative importance and risk level in each failure mode.Taking the function failure of balise system as an example,the weights from each failure mode can be obtained by analytic network process(ANP)method.With fuzzy evidence theory,the risk level score can be translated into basic probability assignments(BPA)function evaluation matrix for generating the risk analysis on function failure.The evaluation results showed that ANP can be applied to calculate the weights of interconnected systems for each facility,and fuzzy evidence theory can efficiently generate the risk assessment based on experts' experience,which can solve the subjectivity and uncertainty problems during the risk assessment procedures.Finally,according to the risk level secured by the complex judgment,the risk control measures and recommendations were raised from system hardware,software and maintenance,which provided references on improving system design and maintenance strategy.