【作者】 支永健；

【导师】 方攸同；

【作者基本信息】 浙江大学 ， 电机与电器， 2013， 博士

【摘要】 实验室测试结果显示离线引起接触网—受电弓之间的电弧(弓网电弧)是一个频谱很宽的电磁干扰发射源。一方面铁路地面架设的供电导体：接触网、负馈线和钢轨等供电导体构成的多导体传输线(Multiconductor Transmission Line MTL)为弓网电弧电磁干扰的传播提供了回路,另一方面沿着地面架空MTL传播的弓网电弧电磁干扰也向外辐射电磁波,影响铁路沿线电子敏感设备的正常工作。这些为电磁干扰提供传播路径的MTL都架设的大地之上,大地是一个由固体颗粒、水和空气构成的复杂不均匀混合体,由于长期的沉积作用,明显表现出水平分层特性。由于在分层结构表面吸附表面波(trapped surface wave)的存在,弓网电弧电磁干扰沿分层土壤表面的电磁辐射也发生明显变化,同时也影响了电磁干扰沿架空MTL的传播特性。为了简化分析本文把土壤看成是二层结构,其中下层土壤厚度为无穷大,分别研究了AT变压器、轨道电路和二层土壤对电气化铁路弓网电弧电磁干扰传导和辐射传播的影响。本文基于多导体传输线理论的时域有限差分法(Finite-Difference Time-Domain FDTD)研究了弓网电弧电磁干扰沿架空多导体的传导干扰传播特性,首先根据研究对象不同分别把架空多导体等值合并为三导体和四导体传输线,计算了多导体的二层土壤自阻抗和互阻抗矩阵,并用矢量匹配法得到了该阻抗值的近似结果。考虑到AT变压器和轨道电路设备对电弧电磁干扰的传导影响较大,介绍了基于试验和矢量匹配法得到等效电路的步骤,并根据它们等效电路的状态变量方程和输出方程,推出了集总元件(AT变压器和轨道电路设备)连接在多导体终端和中间时的FDTD迭代公式。从推出的结果可以看出由于AT变压器和轨道电路设备不是连接在主动线(Active Line)和参考线之间而是连接在主动线和主动线之间,使得FDTD迭代公式中的矩阵不再是对角线矩阵,增加了求解时间。弓网电弧电磁干扰没有成熟的数学模型,而梯形电压波可以很方便地调节参数模拟不同带宽的干扰源,所以本文基于以上推导的迭代公式以梯形电压波作为弓网电弧电磁干扰源研究了不同带宽电磁干扰源的传播特性；二层土壤通过影响电报方程中的地阻抗而影响电弧电磁干扰的传导,通过改变上层土壤的厚度研究了不同土壤结构对电磁干扰传播的影响；由于弓网电弧的发生位置是随机的,且同时也可能连续发生多个干扰源,本文研究了弓网电弧距AT变压器不同距离和单个、双个电磁干扰源的传播特性。最后论文研究了二层土壤结构对弓网电弧电磁干扰辐射传播的影响,基于频域麦克斯韦方程推导了架设在二层土壤上无限长导体的场分量积分表达式,根据围道积分理论得出在土壤表面的场,包括直射波、反射波、侧面波和吸附表面波,分析得出该吸附表面波由被积函数的极点留数决定,与上层土壤厚度有很大关系(在一定厚度下吸附表面波占主要成分),且离开地面以后迅速衰减的结论。并指出了电气化铁路电磁干扰测试中由于天线距离地面1—3米,此时吸附表面波几乎已经衰减完,不能反映出地面吸附表面波的情况。分析结果显示,地面电子敏感设备建设仅依据测试结果是不行的,还要参考施工地点大地的电磁特性,最好能测试出贴近地面的电磁干扰值作为一项重要的附加参考指标。更多还原

【Abstract】 Laboratory test results show that Electro-Magnetic interference of pantograph-catenary arcing, which has a wide frequency specturm, is a powerful interference source. On the one hand, the conductors of traction power:catenary, feeder, rails and so on, constitute the multi-conductor transmission line (MTL). Therefore, the EMI of pantograph-catenary arcing can propagate along the MTL. On the other hand, the electromagnetic wave radiated by the EMI signals through the MTL can affect the normal operation of sensitive electronic equipments along the railway line. All the MTLs are set up above the lossy earth. Due to the long-term deposition, the lossy earth, which composed of a solid particles, water and air, shows obviously characteristics of multi-layer. Because of the trapped surface wave existed in the surface of hierachy, the propagation of EMI signals along the MTLs has undergone a significant change. In order to simplify the analysis, the earth is modelled as two-layer structure, and the lower layer is infinite. This thesis gives an investigation of the influence of auto-transformer, track circuit. Also analysis the propagation characteristic of EMI signals in the two-layer earth structure, which produced by pantograph-catenary arcing.This thesis presents the propagation characteristic of pantograph-catenary arcing EMI, based on Finite-Difference Time-Domain (FDTD) method of MTL. Firstly, the overhead MTL are equivalent to three or four conductors according to the different research objects. The self and mutual impedance matrix of two-layer soil are calculated, which is approximated by vector matching. Secondly, considering the influence to the electromagnetic wave propagation of EMI signals by the AT transformer and track circuit equipment, the steps to obtain the equivalent circuit is presented. Moreover, according to the state equation and output equation of the equivalent circuits, the FDTD iterative equation of the lumped element connected the MTL terminal and intermediate is deduced. From the results, we can see that the iterative formula is no longer a diagonal matrix, because the auto-transformer and the track circuit equipment is not connected between the the active line and the reference line.Based on the FDTD iterative formula, the trapezoidal voltage wave as the mathematical model of the pantograph-catenary arc electromagnetic interference sources is adopted. By adjusting the rise and fall times of the trapezoidal, the bandwith of EMI can be tuned. Therefore, the propagation characteristic of EMI with different bandwidth of soure can be analysised. The ground impedance of two-layer earth can affect the propagation characteristic of EMI, and thus, this thesis also disscuss the influence of different depth of two-layered earth on the propagation characteristic. Meanwhile, the propagation characteristic v.s. the distance between the arcing point and the auto-transformer and the number of AT are also analysised.Finally, the thesis studies the influence of the two-layer earth structure on the propagation charecteristic of EMI. Based on the frequency-domain Maxwell equation, the integral formula of infinitely long wire above the two-layer earth is derived. According to the contour integral theory, the total field in the surface of earth consists of direct wave, reflected wave, lateral wave and trapped surface wave. It is noted that the trapped surface wave is determined by the pole residue of the integrand. Meanwhile, it is demonstrated that the amplitude of trapped surface wave decay rapidly when leaving the ground. Based on the analysis of this thesis, it concluded that when the antenna above the earth1-3meters, the trapped surface wave can be neglected. Therefore, the testing standard of Railway applications-EMC could not show propagation charactersitc of the trapped surface wave. Meanwhile, the analysis results show the test results are not enough when the sensitive electronic equipment is close to the earth. An importamt additional test of electromagnetic interference close to the earth is essential.更多还原