Outdoor overhead cable
The overhead contact network (also known as overhead cable) is one of the two common power supply networks for electrified railways, and the only power supply mode for trolley buses. In the railway and urban rail transit systems, the overhead contact network has only one electrode of the conductor. The electric locomotive gets electricity through the electric bow and then returns to the grid through the metal wheel rail. In the system where the rubber wheels are used, such as the trolley, the overhead contact network has one positive and one negative two parallel contact wires (contact wire for short), which take electricity through two sets of poles and form a path.
Simple suspension only wire, no load line, advantages are simple structure, low column height, support point to bear a lighter load, generally used in the tunnel, such as low clearance. Simple suspension is also widely used on urban light and trackless trams. The disadvantage is that the span is small, the suspension point has a hard point, and in the operation of the wire oscillations, not suitable for high-speed railway.
The chain suspension
The catenary suspension connects the conductor and the bearing line with the suspension cable, which solves the problem of small span and hard point in the simple suspension, so it is widely used in the long distance, high speed and large span electrified railway. In urban metro, if the chain suspension is used, the running speed is expected to be above 120km/h.
Rigid suspension is a new mode of suspension in which hard metal strips (usually copper strips) replace flexible wires. With the development of material science and structural mechanics, the rigid suspension makes use of the advantage of large contact area of the power supply of the third rail, and overcomes the disadvantage that the rail is too heavy to be suspended. When the urban rail transit is opened from the underground line to the above-ground line, it is directly connected with the elastic suspension line seamlessly, without replacing the locomotive. At the same time, due to the rigid suspension using the collector bow, the third rail without the collector boot is easy to fall off, which can achieve higher running speed. However, the disadvantage is that the contact area between the rail and the pantograph carbon bar is large, and the loss to the pantograph carbon bar is also large.