**作者：**Yaw-Juen Wang**中文摘要：**Knowledge of frequency-dependent impedance is essential for transient and harmonic analyses of a DC traction power system. This paper deals with the skin effect of the power rail (also known as the conductor rail or third rail) used in the Taipei Rapid Transit System (TRTS). The method of coupled-inductance based on subdivision of conductors is employed to calculate the current distribution and the frequency-dependent impedance of the power rail under the skin effect. This paper also proposes a method to reduce the number of subconductors required to achieve a prescribed level of accuracy at high frequency so that computation time and matrix dimensions are reduced.**英文摘要：**--**中文關鍵字：**skin effect, traction power systems, power rail, frequency-dependent impedance**英文關鍵字：**--