Research on wideband modeling of multi-core twisted cables utilized for high-speed railway signaling systems

In order to study transient overvoltage characteristics of multi-core twisted cables utilized for high-speed railway signaling systems, the deficiencies of the available cable transient modeling were analyzed and an improved modeling method was proposed. This improved modeling method was performed in two steps: cascade transmission line parameter calculation for a length of one twist cycle and the wideband equivalent model of multi-conductor transmission lines for multi-core twisted cables in the time domain. This modeling method considers the influence of the proximity effect and skin effect among the core wires as well as the twisted features of the cable. As a validation, the experiment of the transfer impedance and transmission characteristics under lightning impulse was conducted. It shows good correspondence between simulations and experiments. The wideband model for multi-core twisted cables of two star quads was established. In addition, the effects of several important factors influencing the magnitude of the lightning transient overvoltage were analyzed. The basic characteristics were as follows: The cable shields grounded at both ends can significantly limit the transient over-voltage amplitude of cable wires. The spare wire shorted to ground will reduce the open-circuit transient voltage of active wires. © 2016 Chin. Soc. for Elec. Eng.