The history of metro systems dates back to the 19th century when the first underground railways were built. The London Underground, commonly known as the Tube, is often considered the world’s first metro system. It opened in 1863 and used steam locomotives to transport passengers through underground tunnels. Other cities soon followed suit, with Budapest opening the first electrically powered underground railway in 1896.
Over the years, metro systems have evolved and expanded in cities worldwide. They have become a crucial part of urban transportation infrastructure, providing a convenient and efficient means of moving large numbers of people within cities.
In terms of power supply, metro systems typically rely on electricity to operate. The methods for supplying power to metros can vary, but there are a few common approaches:
Third Rail System: This is the most common method used by many metro systems. It involves an electrified rail, known as the third rail, placed alongside or between the running rails. Electric trains draw power from the third rail through contact shoes or pantographs attached to the train’s underside. The third rail carries direct current (DC) electrical power, typically at voltages ranging from 600 to 750 volts.
Overhead Lines: Some metro systems, especially those with above-ground sections or light rail systems, use overhead lines to supply power. These lines consist of wires suspended above the tracks. Electric trains collect power from the overhead lines using pantographs, which are mounted on the train’s roof. The overhead lines typically carry alternating current (AC) electrical power.
Battery-powered Systems: In some cases, especially for newer and more environmentally friendly metro systems, battery-powered trains are used. These trains carry onboard batteries that store electricity. The batteries are charged either through regenerative braking (where the train’s momentum is used to generate electricity) or through dedicated charging infrastructure at stations.
It’s worth noting that the specific power supply method can vary from city to city, depending on factors such as technological advancements, infrastructure requirements, and safety regulations. Additionally, metro systems often have sophisticated power distribution and control systems to ensure the efficient and reliable operation of trains.