| Summary: | 碩士 === 中原大學 === 電機工程研究所 === 95 === Abstract
For developed countries, subway systems significantly improve the traffic flow in metropolitan areas. It has been more than one hundred years since United States and European countries developed integrated public rapid transit systems. Taiwan is a mountainous island and most of the population is located in several metropolitan areas around the island. Traffic congestion has been a chronic problem in those areas which can not be solved easily by creating more efficient traffic control, increasing road areas, etc. Therefore railroad transportation becomes an important means of improving metro traffic situation. Railroad transportation has two categories: traditional trains and metro rapid transits (also known as subways). Traditional trains serve best to provide long distance transportation but help little in solving inner city traffic congestion, while rapid transit systems are targeted to provide smooth and rapid transportation in urban areas. Metro rapid transit systems mainly consist of trains powered by electricity. Depending on environment, electricity can be supplied to trains in two different ways: supply from overhead or supply using the third track. The electricity system needs to have a stable supply structure to ensure smooth and safe operation of the rapid transit system. Any malfunction of the electricity supply system needs to be isolated using proper operation of protective relays depending on each specific malfunctioning scenario. In addition, electricity interruption should be limited to the smallest area possible by means of the operation of circuit breakers while maintaining regular power supply for the rest of the system. Therefore protective relays, circuit breakers, PT, CT, and related control circuits must be maintained in ideal situation in case of emergency situations. The design of protective relay systems in a rapid transmit power system is a critical and delicate task. The main and backup protections need needs to be coordinated. In practical design, protective features like the switching time of circuit breakers, characteristics of protective relays, and the tolerance of PT and CT are all important factors to be considered.
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