城市轨道交通杂散电流动态概率分布特性及其对电力主变影响研究

The stray current and its prevention have always been a problem in urban rail transit system. With the operation of large-scale, high-density and web-forming urban rails, the distribution of stray current becomes more complicated. Monitoring shows that stray current in urban rail transit system brings about DC magnetic bias of main transformer, resulting in new challenges to the transformer’s normal operation. This project proposes the research of dynamic probability distribution of stray current in urban rail transit system and its influence on main power transformer under web-forming conditions for the first time. By establishing the stray current distribution model under complicated geological environments and dynamic operation conditions, the dynamic probability distribution characteristics of stray current of different positions in urban rail transit system are analyzed based on the random fluctuation of loadings and earth conditions under web-forming conditions. Besides, according to the distribution and transmission pattern of stray current flowing into the main transformer, the quantitative evaluation method of power transformer DC bias is researched from the perspective of statistics, and its impact on main transformer is studied. Thus the optimization and prevention method is proposed. This project incorporates theoretical modeling, simulation analysis, and verification by practical data, aiming at revealing the dynamic probability distribution characteristics of stray current under complex conditions in urban rail transit system and evaluating its impact on power transformer DC bias. Therefore effective mitigating schemes are expected to be put forward to improve the safety and reliability of the urban rail transit power supply system and urban power system.

城市轨道交通系统产生的杂散电流及其防护一直是个难题，特别是随着大规模、高密度、网络化城轨系统的运行，其杂散电流分布更加复杂；监测发现城轨杂散电流引发电力主变直流偏磁现象存在，给主变的安全运行带来了新的挑战。项目首次提出成网条件下城轨杂散电流动态概率分布特性及其对电力主变影响的研究。通过建立基于复杂地质条件和动态运行条件的城轨杂散电流分布模型，并在考虑成网条件下供电负荷及土壤条件随机波动的基础上，研究不同位置城轨杂散电流的动态概率分布特性；同时，基于流入主变的杂散电流分布特性与传播规律，从统计角度研究电力变压器直流偏磁量化评估方法，以及其对主变的影响和危害程度，并提出优化抑制方法。项目采用理论建模、仿真分析、实测验证相结合的方法，旨在揭示城轨系统中杂散电流在复杂多重条件下的动态概率分布特性，定量评估其对电力主变直流偏磁的影响，提出有效抑制方案，以提高城轨供电系统和城市电网的安全可靠性。

随着城轨大规模、高密度、网络化发展，城轨持续运行产生大量杂散电流。城轨线路与城市电网在空间上交错分布，大量的直流杂散电流入侵城市电网，导致主变直流偏磁现象发生，给主变的安全运行带来了新的挑战。首先，本项目研究了有限元法、解析法及仿真法对建立城轨多区间杂散电流分布模型的适应性，并在此基础上针对城轨贯通供电结构，提出城轨长线路杂散电流分布模型，研究了复杂地质条件、回流系统参数、列车动态运行等对城轨杂散电流分布的影响；通过分析城轨杂散电流入侵城市电网的大地及架空地线双重路径，基于地铁杂散电流在电网中的路径分布，提出并建立了城轨杂散电流与电网耦合模型及电网主变直流偏磁电流分布模型，并通过实测数据验证模型的正确性；为进一步挖掘电网主变直流偏磁特征，本项目设计并研发了电网主变直流偏磁电流同步测量装置，对深圳、贵阳等城市电网主变中性点直流、振动及噪声进行同步监测及分析，明确了不同城市主变直流偏磁范围及影响程度；然后，基于主变振动信号的时频特征，提出基于频率能量比及小波熵的主变直流偏磁隐患辨识方法；并基于主变中性点直流中性点分布，提出自适应均流控制算法；最后研发了主变直流偏磁监控系统，并在深圳片网实现应用，实现片网主变直流偏磁特征同步检测及主变直流偏磁综合抑制。