近年臺鐵西部幹線都會區鐵路捷運化之轉型，路線容量近趨飽和，設備故障所致之營運影響更顯重要，電車線系統可靠度直接影響營運安全與服務品質，故提高電車線系統可靠度是緊迫關鍵的問題。本研究依歐洲標準EN50126之原則，以故障樹分析法對臺鐵西部幹線(含山線與海線)電車線系統進行可靠度定性及定量分析，結果顯示主吊線是電車線系統最薄弱的環節，必須進行改善工作；每百公里之電車線系統平均故障間隔時間MTBF約為198日，對於系統保養週期訂定提供重要參考。本研究也探討電車線系統可維修度、妥善率，闡述RAMS之內在關聯性，並提出營運階段可靠度改善方案，如下：採用較高可靠度的組件；採用較易更換、模組化的組件；培養訓練有素且經驗豐富的檢修人員。

In recent years, the Western Line of Taiwan Railway Administration (TRA) in the metropolitan areas have been rapid transit systematized. At the same time, the line capacity is near saturation. Therefore, the impact from electromechanical equipment failures on the operation is becoming more significant. The reliability of the overhead catenary system affects the operational safety and service quality directly, so the improvement of the overhead catenary system reliability is definitely an important and urgent issue. In accordance with the principles of the European Standard EN50126, both the qualitative and quantitative analyses of reliability on the overhead catenary system of the TRA Western Line (both the Mountain Line and the Coast Line are included) were conducted with the fault tree analysis method. The results show that the messenger wires are the weakest link in the overhead catenary system, and therefore the improvement work is needed. The mean time between failures (MTBF) of the overhead catenary system per hundred kilometers is about 198 days, which provides an important reference for setting up the system maintenance cycle. In the study, it also explored the overhead catenary system maintainability and availability, and explained the inherent correlation of the RAMS. Meanwhile, it also proposed solutions to improve the reliability of the operational phase as the follows: adopting high reliability components, adopting easier-to-replace and modularized components, and fostering trained and experienced maintenance personnel.