Research On Method For Detection Of Shunting State Of Track Circuits Based On Travelling Waves

The track circuit is one of the fundamental equipments of train control system. In addition to use for train detection, it also can transmit train movement authority. It is quite important to judge the shunt state of track circuit which is a track section occupied by a train for traffic safety. However, in some sections, the shunt resistance becomes too high due to the rust or dirt on the rail surface that can cause a shunt malfunction problem, and can make the detection become difficult, which has an adverse effect on railway transport safety and efficiency. Aiming at the influence of shunt malfunction, this thesis starts from the time responses of current travelling wave to study the shunt state of track circuit. With the proposed method by the mutation characteristics of the receiving end current for detection the shunt state of track circuit, which can eliminate the effects of shunt malfunction. The main research contents are as follows.Firstly, the whole track circuit is divided into finite segments and all the segments can be cascaded based on uniform transmission line theory and combined with its inherent parameters the transmission line model of track circuit is established. Then, through this model, transmission line equations are deduced. According to the reference of numerical solution method of transmission line equations, a precise time-integration method is chosen to obtain the solutions of track circuit transmission line equations. The truncation error is efficiently decreased by interlacing the voltage and current nodes along the space coordinate which make the computational efficiency rise greatly. At the same time, the boundary conditions of track circuit in adjusting and shunting state are confirmed, and the time domain solutions of travelling wave signals in different state of track circuit are got.Secondly, considering two cases respectively, step and sinusoidal excitations, the time responses of track circuit in adjusting state are simulated by Matlab corresponding to the rail line parameters. Then, the steady-state signal under adjusting state can be regard as the initial condition of shunt state of track circuit. The changes of current travelling wave at the receiving end during the train entering or clearing of track section can be got. Considering the worst condition, the influence of the variations of ballast resistance, supply voltage and shunt resistance are investigated. In addition, the current travelling wave at the receiving end is simulated under the condition of excessively high shunt resistance. The results show that there exists a transient singularity signal when the train entering or clearing of track section, which can be used as the judgment of shunt state of track circuits.Finally, in order to detect the singular point of receiving end current during a train entering or clearing of track section, a singularity detection method based on singular value decomposition(SVD) is studied. The current signal at the receiving end of track circuit is decomposed into a series of approximation and detail components with different resolution by dichotomizing recursion SVD. The signal processing results show that the detail signals at different levels can detect the accurate position of singular point in signal, which verifies the effectiveness of this method.