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Traction current can to impose conductive interference on the railway signalling system, which is also known as unbalanced traction current interference. In the station turnout section, the traction current may cause obvious interference on both receiving apparatus of track circuit and cab signalling apparatus due to the installation of multi-jumpers, wing rails, and insulated joints inside the turnout. This paper analyzes the above structural characteristics of turnouts in depth. By establishing a comprehensive simulation model of one-transmitter and two-receiver track circuit in turnout section and simulating the complete return current path along with traction network–locomotive–rails, the mechanism of traction current conductive interference in the turnout section is then illustrated, using Multisim and MATLAB/Simulink simulation platform. Finally, based on the Analytic Hierarchy Process (AHP), an optimization method of switch jumper setting is studied. The simulation results show that the conductive interference in the turnout section mainly involves two factors: The inherent turnout structure definitely results in different impedance of two rails, and the inductive cab signal is partly bypassed in the turnout center (nose rail). Especially, conductive interference magnitude depends on the jumper location. Therefore, in engineering practice, it is feasible to reduce the interference to a certain degree by reasonable settings of the switch jumper.

The ZPW-2000 track circuit is the dominant track circuit system used in China. On standard plain line track it is used as a jointless track circuit where 'tuned zones' are used to separate adjacent tracks operating at different frequencies. Owing to the complexities of station layouts it is not possible to use the ZPW-2000 as a jointless track circuit within stations, so a solution incorporating mechanical joints is commonly used. The station environment is known to have high levels of electromagnetic interference, and such environments can cause interference in the track circuit resulting in signal degradation and failure. An integrated solution that allows the ZPW-2000 track circuit to be used dependably in jointed operation that is able to cope with the electromagnetic environment found in stations is therefore required. In this study, a solution based on impedance bonds is developed to alleviate interference problems with the ZPW-2000 in harsh electromagnetic environments. The study presents an innovative design of impedance bond incorporating an air gap transformer and a double function filter circuit. The impedance bond was found to have an impedance of below 0.01 Ω at the resonant frequency of 50 Hz, and in excess of 17 Ω at other signal frequencies. The impedance bond is shown to eliminate interference while meeting the requirements of signal transmission on rail tracks. In this study, both theoretical analysis and the results of laboratory tests are presented.

Cab signaling apparatus is the critical equipment for ground-vehicle communication in electrified railways. With the rapid development of high-speed and heavy-haul railways, the immunity to unbalanced traction current interference for cab signaling apparatus in the onboard train control system is increasingly demanded. This paper analyzes the interference coupling mechanism of the ZPW-2000 track circuit. Based on electromagnetic field theory and the actual working parameters, a calculation model is established to complete the quantitative research of the cab signal induction process and traction current interference. Then, a finite element model is built to simulate the process. The simulation results under the signal frequency, fundamental and harmonic interference are all consistent with the theoretical calculation results. The practical measurement data verify the coupling relationship between cab signal inductive voltage and rail current. Finally, an indirect immunity test method applying this relation for the cab signals is proposed, and the voltage indexes of the disturbance sources are determined, i.e., the test limits. The results provide an accurate quantitative basis for the cab signaling research and design of the immunity test platform; besides, the proposed indirect test method can simplify the test configuration and improve test efficiency.

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