| Summary: | 碩士 === 國立臺灣科技大學 === 工業管理系 === 95 === Electrical power for Taipei Metro system EMU, supplied by Taiwan Power Company (TPC) to the Metro System Engineering Department at a potential of 161kV, following receipt by Bulk Supply Substations (BSS) managed by the Department of Rapid Transit (DORT), is stepped down from 161kV to 22.8kV and distributed to downstream Traction Supply Substations (TSS). The TSS, after transforming and rectifying this 22.8kV AC power into 750V DC power, supply positive current to downstream conductor rails to serve as an EMU motive power source. Negative current, after use by the EMU, flows to the running rail via its wheels and returns to the TSS negative bus, completing the DC circuit.
The running rails in a rapid transit system, apart from supporting and guiding the car body, also serve as the traction current return path. Negative EMU current returning to the TSS via the wheel and running rail undergoes a voltage drop (called Rail Potential Rise) due to the electrical resistance from the rail. Whether the rail is located in the DORTS depot or in the main line, the negative and positive traction power current are by design separated, and in the area depot boundary and the main line, Insulated Rail Joint (IRJ) are used to increase the separation. Since the rail between the two extremities of the IRJ belongs to different power systems, there usually exists a potential difference (-50V DC to +200V DC). Each time the EMU wheel leaves the IRJ, an arc will be produced between the wheel and the rail, leading to corrosion between the EMU wheel and the tracks.
Recently, DORTS found the electric potential in the vicinity of Hsiao Pitan Station to be on the high side and the corrosion between the EMU wheel and rails of two extremities of IRJ becoming more serious daily, so in order to thoroughly eliminate this potential risk, relevant units of the DORTS Engineering Department, after considering examples from other advanced industrialized countries, proposed a plan to install equipment to ameliorate the electric potential difference.
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