Newsletter 高速鐵路簡訊 . 交通部高速鐵路工程局
機場捷運牽引動力雜散電流系統介紹 Introduction to the TIAA MRT Traction Power Stray Current System
雜散電流防制措施示意圖。

機場捷運電聯車動力來自設於沿線之牽引動力變電站(Traction Supply Substation,TSS),經由TSS之整流器組將22kV交流電轉換為750V直流電,透過正電電纜傳輸電力至導電軌(第三軌)、負電回流部分則由鋼軌(行車軌)經由負電電纜連接至TSS負電直流盤,形成一完整電流路徑。但當電流流經鋼軌時,在鋼軌上形成電壓降,而鋼軌對地之電阻亦不可能完全絕緣,使得電流從軌道洩出,再經由周遭地表下的金屬管線或結構鋼筋又回到軌道,此種由軌道洩出之電流就是雜散電流。
為抑制雜散電流,減少其對土建結構鋼筋或其他地下金屬管線之危害,機場捷運於設計階段即將雜散電流防制措施納入設計並據以施工。
茲概述如下:
1.上/下行鋼軌間每隔約200公尺以一條240㎜2電纜跨接,以降低負電流回路之電阻值,使得大部分回流電流均可透過鋼軌回至TSS負極端,減少其散逸之機率。
2.鋼軌施工及安裝部分對地絕緣電阻須大於100Ω-km;供電系統設計部分,則採非接地(浮接)設計,以增加鋼軌對地之絕緣電阻值,並隔離將正線與機廠電力以鋼軌絕緣接頭(IRJ)實體隔離,以確保正線鋼軌對地絕緣電阻值,並保障機廠維修區之人員安全。
3.為攔截無可避免之散逸雜散電流,降低其對其他地下金屬管線之危害,特於鋼軌下方設置雜散電流蒐集網(SCCM),以蒐集一次雜散電流,再連結車站結構鋼筋,形成同電位並與雜散電流蒐集網透過回流電纜直接串接,以蒐集二次雜散電流。
為瞭解及監控機場捷運雜散電流變化情形及散逸狀況,於全線TSS機房皆設置雜散電流測試箱,設置可程式控制器(PLC)紀錄該區段雜散電流量測資料,再即時傳送至青埔機廠主維修工廠TSS內之「雜散電流監視系統(SCMS)」,以即時顯示、監測及記錄全線雜散電流變化情形,做為系統監測之長期參考。

The traction power of TIAA MRT EMUs is generated from the traction supply substations (TSS) along the MRT line. The power is alternated from 22kV AC power into 750V DC power through the TSS rectifier and provides power to the conductive rail (third rail) via positive electricity cable; the negative backflow is connected by the rail (running rail) to a TSS negative DC switchgear via negative cable to form a complete current path. However, when the current flows through the rail forming voltage drop on the rail causing the rail resistance to the ground unable to be completely insulated, current is dissipated from the rail which returns back to the track via the surrounding metal pipeline or structural steel. This kind of current is called the stray current.
In order to curb the stray current and reduce its damage to the civil structure of reinforced steel or other underground metal pipelines, the TIAA MRT was designed and constructed in accordance with the stray current control measures at its design stage.
The mechanism is briefed as follows:
1. The northbound/southbound rails are bridged across a 240 mm2 cable every 200 meters to reduce the resistance of the negative current path so that most of the return current can return to the TSS negative terminal through the rail to reduce its chances of dissipation.
2. The ground insulation resistance of rail construction and installation must be greater than 100Ω-km; as for the power supply system design, the system adopted the ungrounded (floating) design to increase the rail insulation resistance to the ground. The power of the main line and depots are insulated by the insulated rail joint (IRJ) to ensure the insulation resistance of the rail to the ground and to protect the safety of the personnel in the maintenance area of the depot.
3. In order to intercept the dissipated stray current to reduce its damage to other underground metal pipelines, the stray current collector mats (SCCM) are especially set below the rail to collect the primary stray current. Then, the cycle will connect with station steel structures to form idiostatic potential and link directly to the SCCM through the return cable to collect the secondary stray current.
To understand and monitor the TIAA MRT stray current changes and dissipation situation, stray current test boxes are installed in the TSS rooms along the entire MRT line. The PLC in the test boxes will record the stray current measurement data of the section and transmit it to the “stray current monitoring system (SCMS)” in the TSS of the main workshop of Chingpu depot to real-time display, monitor and record the stray current variation of the entire line as a long-term reference for system monitoring.

  • 雜散電流示意圖。
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