Transient Analysis of ZPW-2000 Track Circuit Based on FDTD Interface Method

A track circuit performs a transient process when a train enters or departs a section. Therefore, its circuit state can be judged by the transient change of signals at the receiving end. The finite-difference, time-domain (FDTD) is a common numerical solution for the transmission line. However, the structure of the ZPW-2000 track circuit is more complex than that of general ones. Thus, the direct FDTD method does not work well. Therefore, an FDTD-based transient analysis method and an alternative transient program-electromagnetic transients program (ATP-EMTP) interface model for a ZPW-2000 track circuit is introduced. The entire module is divided into two parts: transmission line and centralised parameter network. The two parts are related by a controlled current source. The transmission line is solved using FDTD, and the centralised parameter network is solved using the ATP-EMTP. The simulation results of the ZPW-2000 track circuit show that the ballast and shunt residences have great impacts on the receiving-end signals. When the ballast resistance falls to 0.6 Ω•km, the receiving-end voltage drops from 2.0 V to about 0.5 V; when the shunt resistance increases to 0.2 Ω, the residual voltage at the receiving end rises to about 1.0 V. If only the threshold comparison method is used, the state of the track circuit is indistinguishable. However, a transient mutation ccurs in the receiving-end signals when the train enters or departs. This can be used to determine the shunt state of the track circuit.