The Research Of Crosstalk On Shielded Cables Of The Locomotive

The anti-interference technology of locomotive shielded cables was researched in this paper in detail based on the transmission line theory. The crosstalk of shielded cables and anti-interference methods were systematically analyzed, too.Firstly, the crosstalk models were established in low frequency based on lumped parameter and high frequency based on distributed parameter theory respectively, then the relationship between crosstalk voltage and frequency was given. And the parameters of distributed capacitance and inductance were calculated. Secondly, the shielding models of electric field and magnetic field were discussed based on lumped parameter theory from which the relationship between shielding efficiency and earthing patterns were concluded. Then parameters of distributed capacitance and inductance of shielded cables were derived, and the crosstalk between shielded cables was calculated with electricity source as interference source.Crosstalk simulation model of shielded cables was set up based on the above theories, The relationships between crosstalk voltage and related parameters were analyzed by programming with MATLAB. Finally, a novel method of measuring the crosstalk was presented according to the simulation model. The crosstalk testing device of shielded cables was designed using the coaxial-cable, and the crosstalk voltages under different conditions were measured both in the frequency domain and time domain. In the frequency domain, the method of RF induction was used to generate the common mode current in the interference cable. In the time domain, surge signal was injected into the interference cable to simulate the unipolar surge caused by transient over-voltage of switches or lighting. At last, common coupling currents under different conditions were measured both in the frequency domain and time domain with this experimental device. The experimental results show good consistency with theoretical analysis. On these grounds, anti-interference methods in the locomotive shielded cables can be obtained, which can be helpful for our practical cabling.