The first electrified railway in the world was laid by Siemens and Halske at the Berlin Trade Fair in 1879, with a length of 300 meters and a gauge of 1000 mm. Since then, with the development of science and technology, the increase of railway traffic and the emphasis on energy utilization, the operating mileage of electrified railways in the world has increased year by year. By the early 1990s, among the 6.5438+0.3 million kilometers of railways, electrified railways were 6.5438+0.8 million kilometers, accounting for 654.38+0.3% of the total railway mileage.
China Railway Electrification Project started on June 1958. 1961August 15, the first electrified railway in China-Baoji-Fengzhou section of Baocheng line was completed and opened to traffic, which significantly improved the transportation efficiency and opened the prelude to the construction of electrified railways in China. Under the guidance of the policy of "giving priority to electric power, giving priority to internal combustion" and "vigorously developing electric traction", by the end of 1990, China had built 16 electrified railways with a mileage of 7,000 kilometers.
The traction power of electrified railway is electric locomotive, which has no energy, and the required energy is provided by power supply system of electric traction. Traction power supply system mainly refers to traction substation and catenary. Substation is located near the railway, which transmits the current of power plant to the catenary above the railway through high voltage transmission lines. Catenary is a device that directly transmits electric energy to electric locomotives. Along the two sides of the railway line, a row of columns are erected, on which metal wires are hung, which is the catenary and can also be regarded as the artery of electrified railway. The electric locomotive uses the pantograph on the roof to obtain electric energy from the catenary and tow the train. According to the current system of catenary, traction power supply system can be divided into DC system and AC system. DC system provides DC power to catenary after the traction substation steps down and rectifies the high voltage and three-phase power supply. This is the earliest developed current system, which has been rarely used since 1950s. The AC system is to reduce the voltage of the high voltage and three-phase power supply in the substation to single phase, and then provide AC power to the catenary. The voltage of AC power supply is relatively high and develops rapidly. The traction power supply system of electrified railways in China has adopted a single-phase power frequency (50 Hz) 25 kV AC system from the beginning, which is beneficial to the development of electrified railways in the future.
With the application of new technologies and new materials, electrified railways have made great progress in quantity and quality, and electrified railways have become an important symbol of railway modernization in the world. It is estimated that by the year 2000, the total mileage of electrified railways in the world will reach 250,000 kilometers, and that of electrified railways in China will exceed 20,000 kilometers, accounting for about 25% of the total mileage of railways in China and 50% of the railway traffic. By then, China electrified railway will enter the advanced ranks in the world in terms of mileage, technical equipment and passenger and freight volume.