Newsletter 高速鐵路簡訊 . 交通部高速鐵路工程局
機場捷運系統雜散電流監視規劃之介紹 Introduction to TIAA MRT Stray Current Monitoring System
機場捷運系統雜散電流監視系統外觀。

理想之捷運直流負回流系統設計,應使負回流電流完全經由鋼軌匯集到整流器負電端,但實際上當電流流經鋼軌時,會在鋼軌上形成電壓降,且鋼軌對地之電阻亦不可能完全絕緣,使得部分電流從鋼軌洩出,再經由周遭地表下的金屬管線或結構鋼筋回到鋼軌,此洩出之電流即是「雜散電流」。
系統雜散電流洩漏量乃直接取決於鋼軌對地電位,其大小與鋼軌本身電阻及鋼軌對地電阻有關,亦與鋼軌與大地接地方式有密切關聯,故桃園機場捷運於系統設計時,除採用「非接地(浮接)系統」直接增加鋼軌對地電阻值,減少雜散電流洩漏量外,又利用鋼軌下方軌床之結構鋼筋形成「雜散電流蒐集網」,避免雜散電流自軌床洩出,再透過「雜散電流回流電纜」以攔截及回收雜散電流,減少流過地下金屬管或結構鋼筋而產生之「電蝕現象」。又雜散電流係分佈於整個捷運路網沿線,其回流路程也是分散於全線,為瞭解全線雜散電流洩漏狀態,故於全線各牽引動力變電站設置可程式控制器紀錄該區段雜散電流量測資料,再傳送至青埔機廠主維修工場牽引動力變電站內之「雜散電流監視系統」(架構及外觀如下二圖示),即時顯示、監測及記錄全線各期程(興建期、系統通電無載期、試運轉期及正式營運期)雜散電流變化情形,藉以建立完整歷史資料庫,作為後續站體結構、周遭管線及軌道系統維護之參考。

The ideal MRT return current system should be designed so that the negative return current runs back to the negative end of rectifier entirely via rails. However, when a current flows through the rails, it forms a voltage drop in the rail. Additionally, resistance of the rail against the ground is also unlikely to be fully insulated thus causing "stray currents" to escape from the rail and returning back to the rail via underground metal pipelines or structural RC.
The amount of stray current is directly dependent to the electrical potential of the rail. The amount is influenced by the rail's resistance and its ground resistance and also closely influenced by the grounding method of the rail. Therefore, TIAA MRT adopted the "ungrounded system" to directly increase ground resistance of the rail and reduce the amount of stray current leakage. In addition, SCCM is formed using structure RC under the rail to avoid current leakage from the rail bed. Then, SCRC is used to collect the stray currents to reduce electrical corrosion caused by current flowing through metal pipelines or structure RC. On account of recording the stray current as well as the return current which flows through the entire MRT rail network, PLCs are distributed in every TSS to measure and record the stray current leakage amount of that section. The data is then collected and sent to the TSS in Chingpu Depot main workshop and displayed, monitored and recorded through the SCMS (see figures for its structure and appearance). MRT rail network stray currents in all phases including initial phase, power supplied phase, operational test phase and official operation phase will be recorded forming a complete database which will be the reference for future station structures, pipelines and rail system maintenance.

  • 機場捷運系統雜散電流監視系統架構。
  • 分享: