Research On The Transient Electromagnetic Effect From High-speed Railway’s Traction Power System To Signal Cable

As the infrastructure of railway transportation, signal system plays an important role in guaranteeing the dispatching and commanding of trains and controlling the operation of trains. Its safety during the operation process is of great significance. In the context of rapid development of high-speed electrified railways, it is quite urgent and necessary for us to study the strong electromagnetic interference caused by traction power system, especially caused by traction current system to the signal devices, as well as the transient electromagnetic effects of the train under the conditions of special operating mode or traction network fault.Under this background, the transient electromagnetic effects of the traction power system and the train’s special operating conditions on signal cables and facilities are explored in the dissertation. The mainly research contents are as follows:The principle of transient process for the short circuit condition under the traction network fault and the principle of transient process for the train’s passing phase insulator are theoretically dissected. The state and transmission routes of the short-circuit current are analyzed, and the mechanism and ways of disturbing signal equipment are also explored. A mathematical model is adopted to analyze the mechanism of producing transient disturbance during the transient process of the train under special operating modes.In accordance with the characteristics of high-speed railway’s traction power system and trackside signal cables, a model is established to analyze the transient electromagnetic effects based on multi-conductor transmission line. The finite difference time domain method which is more suitable for transient interference calculation and analysis is adopted for mathematical derivation. Combined with characteristics of high-speed railway’s traction power system and practice railway, the finite difference approximation formula including frequency-dependent loss is derived based on Carson’s theories, and the primary per-unit-parameter of the transmission line which is more in line with the actual situation is obtained.By using the simulation model, the transmission of various transient processes produced by traction network and train in the traction current routes and their transient electromagnetic effects on signal cables under the normal operating condition, under traction network short-circuit condition and under the exceptionally special operating conditions are calculated and analyzed, respectively. Combined with alignment joint-test and comprehensive experiments of the newly built high-speed railways, the traction current and signal cable’s measure test data under transient electromagnetic effects are obtained, and a detailed comparative analysis and verification is conducted on the measured data and the calculation results.In terms of the influencing factors like signal cable’s parallel approach length, the train’s operation location, the short circuit location, the grounding mode of signal cable, the ground conductivity and the phase angle during the transient process, a series of important conclusions are reached: the relationships between the calculation results of the signal cable core’s induced electromotive force and the parallel approach length are obtained; the relations between the train’s operation location, the short circuit location and the corresponding signal cable core’s induced electromotive force are analyzed; the calculation results of the signal cable core’s induced electromotive force increases as the ground conductivity gets worse; double-grounding mode has better suppression effect on disturbance than the single-grounding mode, especially for the suppression of high-frequency disturbance component caused by the transient process when the train is passing phase insulator; when the voltage reaches zero at opening/closing, the transient disturbance caused by transient process to the signal cable can be effectively prevented.Centering on the security issues caused by transient electromagnetic interference during the operation of high-speed railways, abundant conclusions are reached through modeling, simulation calculation and measurement in field. The research results provide reference basis and important data for the engineering design of transient interference protection, construction and operation of high-speed railways’ signal system and are of great significance to the guaranteeing of the normal functioning of signal equipment and the safe operation of railways. In the meantime, the results also offer guidance to the selection and setting of the test section for the artificial short-circuit test and the electromagnetic compatibility test during the dynamic acceptance period of the newly built high-speed railways, and the evaluation of the test data.