Research On Electromagnetic Interference On Signal Lines Based On FDTD In Coal Mine

This dissertation focuses on severe electromagnetic interference (EMI) on signal line. The EMI leads to misinformation or failing to report, so it is necessary to do calculation and simulation on EMI on signal line. The main research is as follows:Firstly, according to the actual situation of power lines and signal lines laid in coal mine, multi-conductor transmission line (MTL) model is set up, then MTL equation is derived. With finite difference time-domain (FDTD) method, the interference of voltage and current at every time and space step are calculated.Secondly, according to different load at the end of transmission lines without braiding layer, the influence on signal line with open-circuit, short-circuit, non-linear load is calculated; And the influence under different conditions of different length of transmission lines, distance between the two lines, height of signal lines is also investigated.Thirdly, for signal line with braiding layer, inside and outside MTL systems are established. Through the transfer impedance, the distribution voltage source on braiding layer is derived, and the inside and outside systems are connected, then with FDTD, the EMI on signal line is solved.Lastly, as the parameters of braiding layer determine the transfer impedance, thus influencing the shielding effect. In order to find out the basic influential factor, five parameters for calculating the transfer impedance are nondimensionalized. Then the influence of braiding angle and coverage rate to the shielding effect is derived, and their effect on shielding effect is investigated.This dissertation gives full consideration of signal line with braiding layer, and uses the typical signal line and typical interference signal, then gives a much more accurate calculation and simulation of EMI on signal line, which provides a reference for coal mine safety and is essential to lower the accident rate.