交直流双制式牵引供电系统钢轨电位特性分析

交直流双制式牵引供电系统中机车过分相前、后工作于不同供电制式，造成了牵引回流特性的差异，影响不同区段钢轨复合电位分布. 采用CDEGS软件建立了交直流双制式牵引供电系统仿真模型，并验证模型正确性和有效性. 计及交流区段和直流区段之间牵引回流的相互干扰，提出了适用于交直流双制式牵引供电系统的钢轨复合电位限值，研究了影响钢轨复合电位分布的主要因素及其敏感度. 结果表明:当无电区不设置钢轨绝缘节时，无电区段长度增大则交直流区段牵引回流的相互干扰程度降低，导致无电区钢轨复合电位减小；土壤电阻率增大则交直流区段牵引回流的相互干扰程度增强，导致无电区段钢轨复合电位增大；直流区段过渡电阻越大，则直流区段钢轨复合电位越高. 交直流区段之间的无电区设置绝缘节能够改变回流结构，避免钢轨复合电位超标，以国内首条双制式线路为例，设置绝缘节后可以使钢轨复合电位直流分量从103.92 V降至60.20 V，保障了人身安全. 

Analysis of Rail Potential Characteristics of AC/DC Dual-system Traction Power Supply System

In the AC/DC dual-system traction power supply system, the locomotive works in different power supply modes before and after phase breaking, which results in differences in traction return current characteristics and affects the combined rail potential distribution of different sections. A model for AC/DC dual-system traction power supply system is established by using CDEGS software, and the correctness and validity of the calculation model is verified. Given the mutual interference in traction return current between the AC and DC sections, the combined rail potential limit of the AC/DC dual-system traction power supply system is proposed, and the main factors affecting the combined rail potential distribution and its sensitivity are explored. Results show that when the rail insulation joints are not installed in the power free zone, the increase in the length of the power free zone can reduce the mutual interference in the traction return current between the AC and DC sections, leading to the reduction of the combined rail potential in the power free zone. The increase in soil resistivity can aggravate the mutual interference of traction return currents between the AC and DC sections, resulting in increase in the combined rail potential in the power free zone. The greater the rail-to-ground resistance of the DC section, the higher the combined rail potential for the DC section. The insulating joints in the power free zone between the AC and DC sections can change the reflow structure and avoid the out of limits of the combined rail potential. The first dual-system line in China is taken as an example, showing that the DC component of the combined rail potential can be reduced from 103.92 V to 60.20 V when the insulation joints are installed, which can ensure personal safety.