城市轨道交通直流牵引供电系统中，部分走行轨回流电流泄漏至大地形成杂散电流，易导致埋地金属的电化学腐蚀问题。实际系统中多列车频繁启停使得杂散电流表现为典型的动态信号，时频特征的提取有助于研究其腐蚀行为。本文在建立杂散电流数学模型的基础上，通过S变换提取杂散电流的典型时频分布特征，并基于失重测试及电化学测试研究了典型频率下杂散电流的腐蚀行为。实验结果表明动态杂散电流的直流及低频交流分量均会影响金属的电化学腐蚀过程，且腐蚀速率随电流密度的增大及交流频率的降低而增加。

In DC traction power supply system of urban rail transit, partial return current from running rails may leak to earth and form stray current, which can easily cause electrochemical corrosion of buried metals. Stray current would appear as nonstationary signal due to the frequent start and stop of multiple trains in actual system, while its time-frequency characteristic is conducive to the study of its corrosion behavior. Based on the mathematical model of traction power system, time-frequency analysis of stray current signal has been conducted through S-transform. Furthermore, corrosion behavior of stray current at typical frequencies have been studied based on weight-loss test and electrochemical test. The experimental results show that both DC and low-frequency AC components of dynamic stray current will affect the electrochemical corrosion process of metals, and the corrosion rate rises with the increase of current density and the decrease of AC current frequency.

TM 922；TM 46

国家自然科学基金项目（面上项目，重点项目，重大项目）