Overhead insulated cable
Overhead catenary (also known as overhead cable) is one of the two commonly used power supply network modes for electrified railways and the only power supply mode for trolley cars. In railway and urban rail transit systems, overhead catenary has only one electrode of a conductor. Electric locomotives collect electricity through pantograph, and then return to the grid through metal wheels and rails. In the system using rubber wheels such as trolleybus, the overhead catenary has one positive and one negative two parallel contact wires (called contact wires for short), which take electricity through two collector poles and form a path.
The advantages of simple suspension are simple structure, low pillar height, light load on supporting points, and generally used in tunnels and other low clearance occasions. Simple suspension is also widely used in urban light rail and trolley buses. Its shortcomings are that the span is small, the suspension point has a hard point, and the traverse will oscillate up and down during operation, so it is not suitable for high-speed railway.
Chain suspension connects the conductor and the bearing line by suspension, which solves the problem of small span and hard point in simple suspension. Therefore, it is widely used in long-distance, high-speed and long-span electrified railway. In the urban subway, if chain suspension is used, the running speed is expected to reach more than 120km/h.
Rigid suspension is a new type of suspension in which hard metal bars (usually copper bars) replace soft wires. With the development of material science and structural mechanics, rigid suspension takes advantage of the large contact area of the third rail power supply, and overcomes the shortcoming that the rail is too heavy to be suspended. When urban rail transit runs from underground line to ground line, it is directly connected with the line with elastic suspension without changing locomotive. At the same time, due to the rigid suspension using pantograph, there is no use of the third rail collector shoe easy to fall off the shortcomings of higher operating speed can be achieved. But the disadvantage is that the contact area between the contact rail and the pantograph carbon strip is large, and the loss of the pantograph carbon strip is also large.