The infrastructure of electric rolling stock without fail includes contact networks. Thanks to this provision, the supply of target current collectors is realized, which, in turn, drive vehicles. There are many varieties of such networks, but all of them are a combination of cables, fixing and reinforcing elements that provide power from electrical substations. Also, the contact network is also used for servicing fixed objects, including various crossings and lighting stations.
Contact Network Overview
This is part of the technical structure, which is part of a complex of electrified paths and roads. The main objective of this infrastructure is the transfer of energy from traction substation to electric rolling stock. In order to ensure the possibility of supplying equipment with energy from several substations, the contact network is divided into several sections. Thus, sections are formed, each of which is fed with a separate feeder from a specific source.
Partitioning is also used to facilitate repair operations. For example, in the event of damage to the line, only one section of the power transmission will be stopped. If necessary, faulty wiring can be connected to a working substation, which will reduce downtime. In addition, the railway contact network is provided by special insulators. This decision is due to the fact that accidental arc formation at the time of passage of current collectors can disrupt the main sheath of the wires.
Contact network device
Networks of this type are a whole complex of electrical infrastructure components. In particular, a typical device of this structure includes power cables, special pendants, fittings and its special parts, as well as supporting structures. To date, the instructions apply, in accordance with which the parts, fittings of the contact network and wires undergo a special procedure of thermal diffusion galvanization. Elements made of low carbon and carbon steel are subjected to protective treatment to increase the strength and durability of communications.
Features of air contact networks
Air networks are the most common due to space saving and more efficient organization of electric lines. True, there are also disadvantages of such a device, which are expressed in higher costs for installation and maintenance. So, the air contact network includes a support cable, fittings, wires, arrows with intersections, as well as insulators.
The main structural features of networks of this type are reduced to the method of placement. Communications are suspended on special supports. At the same time, sagging of wires may be noted between the installation points. It is impossible to completely eliminate this defect, but its presence can be harmful to power lines. For example, if the support of the contact network allows severe sagging, then the current collector moving along the cable in the places of the suspension may lose contact with its line.
Rail Contact Networks
In this case, we are talking about the classic design of the contact network. It is the railways that use the largest volumes of materials for the electrification of rolling stock. The wire itself for such purposes is made of electrolytic solid-drawn copper with a cross-sectional area of up to 150 mm 2 . As for the support elements, the contact network of the railways is provided by reinforced concrete or metal installations, the height of which can reach 15 m. The gaps from the axis of the extreme tracks to the outer sides of the supports at stations and sections are no more than 310 cm. True, there are exceptions - for example, In difficult conditions, the technology allows reducing the gap to 245 cm. Traditional methods of protecting wires of this type are used - separation into separate sections, the use of insulators and neutral inserts.
Contact network of a trolley bus
Compared to rail transport, the movement of the trolley does not imply a constant electrical connection with the surface. The requirements for maneuverability are also increasing, which leads to changes in the organization of the electrification infrastructure. These differences determined the main feature of electric networks for trolley buses - the presence of two-wire lines. In addition, each wire is fixed at small intervals and is provided with reliable insulation. As a result, the contact network is becoming more complicated both on straight sections and in the branches and intersections. The features include the widespread use of sectioning with appropriate insulators. But in this case, the sheath not only protects the wires from contacts between each other, but also protects the material at the intersection. In addition, the use of arc current collectors and pantographs is not allowed in the infrastructure of trolleybus networks.
Contact networks of trams
In tram contact networks wires of copper and alloys similar in characteristics are usually used. Also, the possibility of using steel-aluminum wires is not ruled out. Interfacing sections with different suspension heights is performed with a slope of the wiring with respect to the longitudinal path profile. In this case, the deviation can vary from 20 to 40%, depending on the complexity and conditions of the line laying section. In direct sections, the contact network of the tram is zigzag. In this case, the zigzag pitch - regardless of the type of suspension - does not exceed four spans. It should be noted and the deviation of the contact cables from the axis of the current collector - this value, as a rule, is not more than 25 cm.
Conclusion
Despite the technological development of electrification systems, contact networks in the basic design options retain the traditional device. Changes in terms of improving technical and operational parameters affect only some aspects of the use of parts. In particular, the contact network of railways is increasingly supplied with elements that have undergone thermal diffusion galvanization. Additional processing of the element base undoubtedly increases the reliability and durability of the lines, but contributes to a radical technical improvement to a minimum extent. The same applies to tram and trolleybus electric networks, in which, however, lately, fixing devices, strength of reinforcement and parts of suspended structures have been significantly improved.