Research On The Correlation Between EMI And Safety Of Railway Signal

Nowadays, with the continuous development of railway system in China, the scope of strong electromagnetic interference (EMI) such as traction current has been increasing; the impact of performance on the railway signal equipment has been intensifying as well. EMI has become one of the main reasons about which leads to fault on the railway signal equipment, the safety protection for EMI on the railway signal system has been much more complicated as well. In the field of railway, the strong EMI always leads to faults on the railway signal equipment, and these faults have week influence on the driving efficiency, extremely endanger the safety of railway. Especially since the High-speed rail accident of "Yong Wen Line" on July23rd, the research on the safety protection for EMI on the railway signal system has become an attentive problem. So it is necessary to explore an analysis method on the correlation between EMI and safety of railway signal to guarantee the safety and working efficiency for the railway.From the point of relationship between EMI and the safety of railway signal, under the condition of EMI which is accordance with immunity test specification, this paper puts forward a quantitative analysis method on the correlation between EMI and safety of railway signal. At first, on the basis of traditional reliability method of Fault Tree Analysis and Failure Modes and Effects Analysis (FMEA), railway signal equipment is divided into parts of subsystem, fault tree is built, the fault modes, fault effects and final effects when it is affected by EMI are analyzed and the table of FMEA is established. Then, the failure probability of subsystem when it is affected by EMI is calculated referring to the reliability prediction method of counting component in the "Reliability Prediction of Electronic Equipment". After that, based on the expert evaluation method and Analytic Hierarchy Process, the risk occurrence degree ranking for each fault mode is ensured, the weight of risk occurrence degree is calculated and each fault mode is divided into the fail-safety side and fail-danger side referring to its final effect to obtain the fail-danger side probability when the subsystem is affected by EMI. Finally, the fail-danger side probability of the railway signal equipment when affected by EMI which is obtained according to the Bayesian network is compared with the provisions of SIL to preliminarily research the correlation between EMI and safety of railway signal.On this basis, treating ZPW-2000A track circuit as the analytic object, under the condition of the transmitter and receiver is affected by EMI which is accordance with immunity test specification, this paper researches the correlation between EMI and safety of ZPW-2000A track circuit and compares the fail-danger probability of ZPW-2000A track circuit with the provisions of SIL to preliminarily prove the feasibility of the quantitative analysis method on the correlation between EMI and safety of railway signal.In addition, according to the feature of Bayesian network, this paper obtains the information about importance degree and posteriori probability of each root node to find the weak point of the railway signal equipment which a certain extent providing the theoretical basis for the safety assessment of railway signal and safety protection for EMI.