Power supply for railways. Traction network Sectioning of contact network

Contact network is a set of devices for transmitting electricity from traction substations to EPS through current collectors. It is part of the traction network and for electrified rail transport it usually serves as its phase (with alternating current) or pole (with DC); the other phase (or pole) is the rail network. The contact network can be made with a contact rail or with a contact suspension.
In a contact network with a catenary suspension, the main elements are the following: wires - contact wire, supporting cable, reinforcing wire, etc.; supports; supporting and fixing devices; flexible and rigid cross members (consoles, clamps); insulators and fittings for various purposes.
Contact networks with overhead contacts are classified according to the type of electrified transport for which it is intended - railway. mainline, city (tram, trolleybus), quarry, mine underground rail transport, etc.; by the type of current and rated voltage of the EPS powered from the network; on the placement of the contact suspension relative to the axis of the rail track - for central current collection (on mainline railway transport) or lateral (on industrial transport tracks); by type of contact suspension - simple, chain or special; on the specifics of anchoring the contact wire and support cable, connecting anchor sections, etc.
The contact network is designed to operate outdoors and is therefore exposed to climatic factors, which include: ambient temperature, humidity and air pressure, wind, rain, frost and ice, solar radiation, and various contaminants in the air. To this it is necessary to add thermal processes that occur when traction current flows through network elements, mechanical impact on them from pantographs, electrocorrosion processes, numerous cyclic mechanical loads, wear, etc. All contact network devices must be able to withstand the action of the listed factors and provide high quality of current collection in any operating conditions.
Unlike other power supply devices, the contact network does not have a reserve, therefore, increased reliability requirements are placed on it, taking into account which its design, construction and installation, maintenance and repair are carried out.

Contact network design

When designing a contact network (CN), the number and brand of wires are selected based on the results of calculations of the traction power supply system, as well as traction calculations; determine the type of contact suspension in accordance with the maximum speeds of movement of the EPS and other current collection conditions; find the span lengths (mainly according to the conditions for ensuring its wind resistance, and at high speeds - and a given level of elasticity unevenness); choose the length of anchor sections, types of supports and supporting devices for hauls and stations; develop CS designs in artificial structures; place supports and draw up plans for the contact network at stations and stages, coordinating zigzags of wires and taking into account the implementation of overhead switches and sectioning elements of the contact network (insulating connections of anchor sections and neutral inserts, sectional insulators and disconnectors).
The main dimensions (geometric indicators) characterizing the placement of the contact network relative to other devices are the height H of hanging the contact wire above the level of the top of the rail head; distance A from live parts to grounded parts of structures and rolling stock; the distance Г from the axis of the outer track to the inner edge of the supports, located at the level of the rail heads, are regulated and largely determine the design of the elements of the contact network (Fig. 8.9).

Improving the design of the contact network is aimed at increasing its reliability while reducing the cost of construction and operation. Reinforced concrete supports and foundations of metal supports are protected from the electrocorrosive effects of stray currents on their reinforcement. Increasing the service life of contact wires is achieved, as a rule, by using inserts on pantographs with high antifriction properties (carbon, including metal-containing, metal-ceramic, etc.), choosing a rational design of pantographs, as well as optimizing current collection modes.
To increase the reliability of the contact network, ice is melted, incl. without interruption of train traffic; wind-resistant contact pendants are used, etc. The efficiency of work on the contact network is facilitated by the use of telecontrol for remote switching of sectional disconnectors.

Wire anchoring

Anchoring of wires is the attachment of catenary wires through the insulators and fittings included in them to the anchor support with the transfer of their tension to it. Anchoring of wires can be uncompensated (rigid) or compensated (Fig. 8.16) through a compensator that changes the length of the wire if its temperature changes while maintaining a given tension.

In the middle of the catenary anchor section, a middle anchorage is performed (Fig. 8.17), which prevents unwanted longitudinal movements towards one of the anchors and allows you to limit the area of ​​damage to the catenary when one of its wires breaks. The middle anchorage cable is attached to the contact wire and the supporting cable with appropriate fittings.

Wire Strain Compensation

Compensation of wire tension (automatic regulation) of the contact network when their length changes as a result of temperature effects is carried out by compensators of various designs - block-load, with drums of various diameters, hydraulic, gas-hydraulic, spring, etc.
The simplest is a block-load compensator, consisting of a load and several blocks (pulley hoist), through which the load is connected to the anchored wire. The most widely used is the three-block compensator (Fig. 8.18), in which a fixed block is fixed to a support, and two movable ones are inserted into loops formed by a cable carrying a load and fixed at the other end in the stream of a fixed block. The anchored wire is attached to the movable block through insulators. In this case, the weight of the load is 1/4 of the rated tension (a 1:4 gear ratio is provided), but the movement of the load is twice as large as that of a two-6-lobe compensator (with one moving block).

in compensators with drums of different diameters (Fig. 8.19), cables connected to the anchored wires are wound on a small diameter drum, and a cable connected to a garland of weights is wound on a larger diameter drum. The braking device is used to prevent damage to the catenary when the wire breaks.

At special conditions operation, especially with limited dimensions in artificial structures, slight differences in heating temperature of wires, etc., other types of compensators are used for catenary wires, fixing cables and rigid crossbars.

Contact wire clamp

Contact wire clamp – a device for fixing the position of the contact wire in a horizontal plane relative to the axis of the pantograph. On curved sections, where the levels of the rail heads are different and the axis of the pantograph does not coincide with the axis of the track, non-articulated and articulated clamps are used.
A non-articulated clamp has one rod that pulls the contact wire from the axis of the pantograph to the support (extended clamp) or from the support (compressed clamp) by a zigzag size. On electrified railways non-articulated clamps are used very rarely (in anchored branches of a catenary suspension, on some air switches), since the “hard point” formed with these clamps on the contact wire impairs current collection.

The articulated clamp consists of three elements: the main rod, the stand and an additional rod, at the end of which the contact wire fixing clamp is attached (Fig. 8.20). The weight of the main rod is not transferred to the contact wire, and it only takes part of the weight of the additional rod with a fixing clip. The rods are shaped to ensure reliable passage of the pantographs when they press the contact wire. For high-speed and high-speed lines, lightweight additional rods are used, for example, made of aluminum alloys. With a double contact wire, two additional rods are installed on the stand. On the outer side of curves of small radii, flexible clamps are mounted in the form of a conventional additional rod, which is attached to a bracket, rack or directly to a support through a cable and an insulator. On flexible and rigid crossbars with fixing cables, strip fasteners are usually used (similar to an additional rod), hingedly secured with clamps with an eye mounted on the fixing cable. On rigid crossbars, you can also attach clamps to special racks.

Anchor section

Anchoring section is a section of a catenary suspension, the boundaries of which are anchor supports. Dividing the contact network into anchor sections is necessary to include devices in the wires that maintain the tension of the wires when their temperature changes and to carry out longitudinal sectioning of the contact network. This division reduces the damage area in the event of a break in the catenary wires, facilitates installation, technical. contact network maintenance and repair. The length of the anchor section is limited by permissible deviations from the nominal tension value of the catenary wires set by the compensators.
Deviations are caused by changes in the position of strings, clamps and consoles. For example, at speeds up to 160 km/h, the maximum length of the anchor section with bilateral compensation on straight sections does not exceed 1600 m, and at speeds of 200 km/h no more than 1400 m is allowed. In curves, the length of the anchor sections decreases the more, the greater the length curve and its radius is smaller. To transition from one anchor section to the next, non-insulating and insulating connections are made.

Pairing anchor sections

Conjugation of anchor sections is a functional combination of two adjacent anchor sections of a catenary system, ensuring a satisfactory transition of EPS pantographs from one of them to another without disturbing the current collection mode due to the appropriate placement in the same (transition) spans of the contact network of the end of one anchor section and the beginning of the other. A distinction is made between non-insulating (without electrical sectioning of the contact network) and insulating (with sectioning).
Non-insulating connections are made in all cases where it is necessary to include compensators in the catenary wires. In this case, mechanical independence of the anchor sections is achieved. Such connections are installed in three (Fig. 8.21, a) and less often in two spans. On high-speed highways, connections are sometimes carried out in 4-5 spans due to higher requirements for the quality of current collection. Non-insulating interfaces have longitudinal electrical connectors, the cross-sectional area of ​​which must be equivalent to the cross-sectional area of ​​the overhead wires.

Insulating interfaces are used when it is necessary to section the contact network, when, in addition to the mechanical one, it is necessary to ensure the electrical independence of the mating sections. Such connections are arranged with neutral inserts (sections of the catenary where there is normally no voltage) and without them. In the latter case, three or four span connections are usually used, placing the contact wires of the mating sections in the middle span(s) at a distance of 550 mm from one another (Fig. 8.21.6). In this case, an air gap is formed, which, together with the insulators included in the raised contact suspensions at the transition supports, ensures the electrical independence of the anchor sections. The transition of the pantograph skid from the contact wire of one anchor section to another occurs in the same way as with non-insulating coupling. However, when the pantograph is located in the middle span, the electrical independence of the anchor sections is impaired. If such a violation is unacceptable, neutral inserts of different lengths are used. It is chosen in such a way that when several pantographs of one train are raised, the simultaneous blocking of both air gaps is excluded, which would lead to the short circuit of wires powered from different phases and under different voltages. To avoid burning out the contact wire of the EPS, the connection with the neutral insert takes place on the run-out, for which purpose a signal sign “Turn off the current” is installed 50 m before the start of the insertion, and after the end of the insertion for electric locomotive traction after 50 m and for multiple unit traction after 200 m - the sign “ Turn on the current" (Fig. 8.21c). In areas with high-speed traffic, automatic means of switching off the current to the EPS are required. To make it possible to derail the train when it is forced to stop under the neutral insert, sectional disconnectors are provided to temporarily supply voltage to the neutral insert from the direction of train movement.

Catenary sectioning

Sectioning of a contact network is the division of a contact network into separate sections (sections), electrically separated by insulating connections of anchor sections or sectional insulators. The insulation may be broken during the passage of the EPS pantograph along the section interface; if such a short circuit is unacceptable (when adjacent sections are powered from different phases or belong to different traction power supply systems), neutral inserts are placed between the sections. Under operating conditions, the electrical connection of individual sections is carried out, including sectional disconnectors installed in appropriate places. Sectioning is also necessary for reliable operation of power supply devices in general, prompt maintenance and repair of the contact network with voltage cutoff. The sectioning scheme provides for such a mutual arrangement of sections in which the disconnection of one of them has the least impact on the organization of train traffic.
Sectioning of the contact network can be longitudinal or transverse. With longitudinal sectioning, the contact network of each main track is divided along the electrified line at all traction substations and sectioning posts. The contact network of stages, substations, sidings and passing points is divided into separate longitudinal sections. At large stations with several electrified parks or groups of tracks, the contact network of each park or groups of tracks forms independent longitudinal sections. At very large stations, the contact network of one or both necks is sometimes separated into separate sections. The contact network is also sectioned in long tunnels and on some bridges with traffic below. With transverse sectioning, the contact network of each of the main paths is divided along the entire length of the electrified line. At stations with significant track development, additional transverse sectioning is used. The number of transverse sections is determined by the number and purpose of individual tracks, and in some cases, by the starting modes of the EPS, when it is necessary to use the cross-sectional area of ​​the overhead catenaries of adjacent tracks.
Sectioning with mandatory grounding of the disconnected section of the contact network is provided for tracks on which there may be people on the roofs of cars or locomotives, or tracks near which lifting and transport mechanisms operate (loading and unloading, equipment tracks, etc.). To ensure greater safety for those working in these places, the corresponding sections of the contact network are connected to other sections by sectional disconnectors with grounding blades; these knives ground the disconnected sections when the disconnectors are turned off.

In Fig. 8.22 shows an example of a power supply and sectioning circuit for a station located on a double-track section of a line electrified with alternating current. The diagram shows seven sections - four on the hauls and three at the station (one of them with mandatory grounding when it is turned off). The contact network of the tracks of the left section and the station receives power from one phase of the power system, and the tracks of the right section - from the other. Accordingly, sectioning was carried out using insulating mates and neutral inserts. In areas where ice melting is required, two sectional disconnectors with motor drives are installed on the neutral insert. If ice melting is not provided, one manually operated sectional disconnector is sufficient.

To section the contact network of the main and lateral networks at stations, sectional insulators are used. In some cases, sectional insulators are used to form neutral inserts on the AC contact network, which the EPS passes without consuming current, as well as on tracks where the length of the ramps is not sufficient to accommodate insulating connections.
The connection and disconnection of various sections of the contact network, as well as connection to the supply lines, is carried out using sectional disconnectors. On AC lines, as a rule, horizontal-rotating type disconnectors are used, on DC lines - vertical-cutting type. The disconnector is controlled remotely from consoles installed in the duty station of the contact network area, in the premises of station duty officers and in other places. The most critical and frequently switched disconnectors are installed in the dispatch telecontrol network.
There are longitudinal disconnectors (for connecting and disconnecting longitudinal sections of the contact network), transverse (for connecting and disconnecting its transverse sections), feeder, etc. They are designated by letters of the Russian alphabet (for example, longitudinal - A, B, V, D; transverse - P ; feeder - F) and numbers corresponding to the numbers of tracks and sections of the contact network (for example, P23).
To ensure the safety of work on the disconnected section of the contact network or near it (in the depot, on the paths for equipping and inspecting roof-mounted electrical equipment, on the paths for loading and unloading cars, etc.), disconnectors with one grounding blade are installed.

Frog

Air arrow - formed by the intersection of two contact pendants above the switch; is designed to ensure smooth and reliable passage of the pantograph from the contact wire of one path to the contact wire of another. The crossing of wires is carried out by superimposing one wire (usually an adjacent path) on another (Fig. 8.23). To lift both wires when the pantograph approaches the air needle, a restrictive metal pipe 1-1.5 m long is fixed on the lower wire. The upper wire is placed between the tube and the lower wire. The intersection of contact wires above a single turnout is carried out with each wire shifted to the center from the track axes by 360-400 mm and located where the distance between the inner edges of the heads of the crosspiece connecting rails is 730-800 mm. At cross switches and at the so-called. At blind intersections, the wires cross over the center of the switch or intersection. Air gunners are usually fixed. To do this, clamps are installed on the supports to hold the contact wires in a given position. On station tracks (except for the main ones), switches can be made non-fixed if the wires above the switch are located in the position specified by adjusting the zigzags at the intermediate supports. The catenary strings located near the arrows must be double. Electrical contact between the catenary pendants forming the arrow is provided by an electrical connector installed at a distance of 2-2.5 m from the intersection on the arrow side. To increase reliability, switch designs with additional cross connections between the wires of both catenary pendants and sliding supporting double strings are used.

Catenary supports

Contact network supports are structures for fastening the supporting and fixing devices of the contact network, taking the load from its wires and other elements. Depending on the type of supporting device, supports are divided into cantilever (single-track and double-track); racks of rigid crossbars (single or paired); flexible crossbar supports; feeder (with brackets only for supply and suction wires). Supports that do not have supporting devices, but have fixing devices, are called fixing ones. Cantilever supports are divided into intermediate ones - for attaching one catenary suspension; transitional, installed at the junction of anchor sections, - for fastening two contact wires; anchor, absorbing the force from anchoring the wires. As a rule, supports perform several functions simultaneously. For example, the support of a flexible crossbar can be anchored, and consoles can be suspended from the racks of a rigid crossbar. Brackets for reinforcing and other wires can be attached to the support posts.
The supports are made of reinforced concrete, metal (steel) and wood. On domestic trains d. they mainly use supports made of prestressed reinforced concrete (Fig. 8.24), conical centrifuged, standard length 10.8; 13.6; 16.6 m. Metal supports are installed in cases where, due to the load-bearing capacity or size, it is impossible to use reinforced concrete (for example, in flexible crossbars), as well as on lines with high-speed traffic, where increased requirements are placed on the reliability of supporting structures. Wooden supports are used only as temporary supports.

For direct current sections, reinforced concrete supports are made with additional rod reinforcement located in the foundation part of the supports and designed to reduce damage to the support reinforcement by electrocorrosion caused by stray currents. Depending on the installation method, reinforced concrete supports and racks of rigid crossbars can be separated or non-separated, installed directly into the ground. The required stability of undivided supports in the ground is ensured by the upper beam or base plate. In most cases, undivided supports are used; separate ones are used when the stability of non-separated ones is insufficient, as well as in the presence of groundwater, which makes it difficult to install non-separated supports. In reinforced concrete anchor supports, guys are used, which are installed along the track at an angle of 45° and attached to the reinforced concrete anchors. Reinforced concrete foundations in the above-ground part have a glass 1.2 m deep, into which supports are installed and then the cavity of the glass is sealed with cement mortar. To deepen foundations and supports into the ground, the method of vibration immersion is mainly used.
The metal supports of flexible crossbars are usually made of a tetrahedral pyramidal shape, their standard length is 15 and 20 m. Longitudinal vertical posts made of angle bars are connected by a triangular lattice, also made from angle iron. In areas characterized by increased atmospheric corrosion, metal cantilever supports 9.6 and 11 m long are fixed in the ground on reinforced concrete foundations. Cantilever supports are installed on prismatic three-beam foundations, flexible cross beam supports are installed either on separate reinforced concrete blocks or on pile foundations with grillages. The base of the metal supports is connected to the foundations with anchor bolts. To secure supports in rocky soils, heaving soils in areas of permafrost and deep seasonal freezing, in weak and swampy soils, etc., foundations of special structures are used.

Console

Console is a supporting device mounted on a support, consisting of a bracket and a rod. Depending on the number of overlapped paths, the console can be single-, double-, or less often multi-path. To eliminate the mechanical connection between catenaries of different tracks and increase reliability, single-track consoles are more often used. Non-insulated or grounded consoles are used, in which the insulators are located between the supporting cable and the bracket, as well as in the clamp rod, and insulated consoles with insulators located in the brackets and rods. Non-insulated consoles (Fig. 8.25) can be curved, inclined or horizontal in shape. For supports installed with increased dimensions, consoles with struts are used. At the junctions of anchor sections when installing two consoles on one support, a special traverse is used. Horizontal consoles are used in cases where the height of the supports is sufficient to secure the inclined rod.

With insulated consoles (Fig. 8.26), it is possible to carry out work on the supporting cable near them without disconnecting the voltage. The absence of insulators on non-insulated consoles ensures greater stability of the position of the supporting cable under various mechanical influences, which has a beneficial effect on the current collection process. The brackets and rods of the consoles are mounted on supports using heels that allow them to rotate along the track axis by 90° in both directions relative to the normal position.

Flexible crossbar

Flexible crossbar - a supporting device for hanging and fixing overhead wires located above several tracks. A flexible crossbar is a system of cables stretched between supports across electrified tracks (Fig. 8.27). Transverse load-bearing cables absorb all vertical loads from the chain suspension wires, the crossbar itself and other wires. The sag of these cables must be at least Vio the span length between the supports: this reduces the influence of temperature on the height of the catenary suspensions. To increase the reliability of the crossbars, at least two transverse load-bearing cables are used.

The fixing cables take up horizontal loads (the upper one is from the supporting cables of the chain hangers and other wires, the lower one is from the contact wires). Electrical insulation of cables from supports allows servicing the contact network without disconnecting the voltage. To regulate their length, all cables are secured to supports using threaded steel rods; in some countries, special dampers are used for this purpose, mainly for fastening contact suspension at stations.

Current collection

Current collection is the process of transferring electrical energy from a contact wire or contact rail to the electrical equipment of a moving or stationary EPS through a current collector, providing sliding (on highway, industrial and most urban electric transport) or rolling (on some types of EPS of urban electric transport) electrical contact. Violation of contact during current collection leads to the occurrence of non-contact electric arc erosion, which results in intense wear of the contact wire and contact inserts of the current collector. When contact points are overloaded with current during movement, contact electrical explosion erosion (sparking) and increased wear of the contacting elements occur. Long-term overload of the contact with operating current or short-circuit current when the EPS is parked can lead to burnout of the contact wire. In all these cases, it is necessary to limit the lower limit of contact pressure for the given operating conditions. Excessive contact pressure, incl. as a result of the aerodynamic impact on the pantograph, an increase in the dynamic component and the resulting increase in the vertical deflection of the wire, especially at clamps, on air switches, at the junction of anchor sections and in the area of ​​​​artificial structures, can reduce the reliability of the contact network and pantographs, as well as increase the wear rate wires and contact inserts. Therefore, the upper limit of contact pressure also needs to be normalized. Optimization of current collection modes is ensured by coordinated requirements for contact network devices and current collectors, which guarantees high reliability of their operation at minimal reduced costs.
The quality of current collection can be determined by various indicators (the number and duration of violations of mechanical contact on the calculated section of the track, the degree of stability of contact pressure close to the optimal value, the rate of wear of contact elements, etc.), which largely depend on the design of the interacting systems - the contact network and pantographs, their static, dynamic, aerodynamic, damping and other characteristics. Despite the fact that the current collection process depends on a large number of random factors, research results and operating experience make it possible to identify the fundamental principles for creating current collection systems with the required properties.

Rigid cross member

Rigid crossbar - used for hanging overhead wires located above several (2-8) tracks. The rigid crossbar is made in the form of a block metal structure (crossbar), mounted on two supports (Fig. 8.28). Such cross members are also used for opening spans. The crossbar with the uprights is connected either hingedly or rigidly using struts, allowing it to be unloaded in the middle of the span and reducing steel consumption. When placing lighting fixtures on the crossbar, a flooring with railings is made on it; provide a ladder for climbing to the supports for service personnel. Install rigid crossbars ch. arr. at stations and separate points.

Insulators

Insulators are devices for insulating live contact wires. Insulators are distinguished according to the direction of application of loads and the installation location - suspended, tensioned, retaining and cantilever; by design - disc and rod; by material - glass, porcelain and polymer; insulators also include insulating elements
Suspended insulators - porcelain and glass dish insulators - are usually connected in garlands of 2 on DC lines and 3-5 (depending on air pollution) on AC lines. Tension insulators are installed in wire anchorages, in supporting cables above sectional insulators, in fixing cables of flexible and rigid crossbars. Retaining insulators (Fig. 8.29 and 8.30) differ from all others by the presence of an internal thread in the hole of the metal cap for securing the pipe. On AC lines, rod insulators are usually used, and on DC lines, disc insulators are also used. In the latter case, another disc-shaped insulator with an earring is included in the main rod of the articulated clamp. Cantilever porcelain rod insulators (Fig. 8.31) are installed in the struts and rods of insulated consoles. These insulators must have increased mechanical strength, since they work in bending. In sectional disconnectors and horn arresters, porcelain rod insulators are usually used, less often disc insulators. In sectional insulators on direct current lines, polymer insulating elements are used in the form of rectangular bars made of press material, and on alternating current lines - in the form of cylindrical fiberglass rods, on which electrical protective covers made of fluoroplastic pipes are put on. Polymer rod insulators with fiberglass cores and ribs made of organosilicon elastomer have been developed. They are used as hanging, sectioning and fixing; they are promising for installation in struts and rods of insulated consoles, in cables of flexible cross members, etc. In areas of industrial air pollution and in some artificial structures, periodic cleaning (washing) of porcelain insulators is carried out using special mobile equipment.

Catenary

The catenary is one of the main parts of the contact network; it is a system of wires, the relative arrangement of which, the method of mechanical connection, material and cross-section provide the necessary quality of current collection. The design of a catenary (CP) is determined by economic feasibility, operating conditions (maximum speed of movement of the EPS, maximum current drawn by pantographs), and climatic conditions. The need to ensure reliable current collection at increasing speeds and power of the EPS determined the trends in changes in suspension designs: first simple, then single with simple strings and more complex - spring single, double and special, in which, to ensure the required effect, Ch. arr. to level the vertical elasticity (or rigidity) of the suspension in the span, space-stayed systems with an additional cable or others are used.
At speeds of up to 50 km/h, satisfactory quality of current collection is ensured by a simple contact suspension, consisting only of a contact wire suspended from supports A and B of the contact network (Fig. 8.10a) or transverse cables.

The quality of current collection is largely determined by the sag of the wire, which depends on the resulting load on the wire, which is the sum of the wire’s own weight (in case of icy conditions along with ice) and wind load, as well as on the span length and tension of the wire. The quality of current collection is greatly influenced by angle a (the smaller it is, the worse quality current collection), contact pressure changes significantly, shock loads appear in the support zone, increased wear of the contact wire and current collector inserts occurs. Current collection in the support zone can be somewhat improved by hanging the wire at two points (Fig. 8.10.6), which under certain conditions ensures reliable current collection at speeds of up to 80 km/h. It is possible to significantly improve current collection with a simple suspension only by significantly reducing the length of the spans in order to reduce the sag, which in most cases is uneconomical, or by using special wires with significant tension. In this regard, chain hangers are used (Fig. 8.11), in which the contact wire is suspended from the supporting cable using strings. A suspension consisting of a support cable and a contact wire is called single; if there is an auxiliary wire between the support cable and the contact wire - double. In a chain suspension, the supporting cable and the auxiliary wire are involved in the transmission of traction current, so they are connected to the contact wire by electrical connectors or conductive strings.

The main mechanical characteristic of a contact suspension is considered to be elasticity - the ratio of the height of the contact wire to the force applied to it and directed vertically upward. The quality of current collection depends on the nature of the change in elasticity over the span: the more stable it is, the better the current collection. In simple and conventional chain hangers, the elasticity at mid-span is higher than that of the supports. Equalization of elasticity in the span of a single suspension is achieved by installing spring cables 12-20 m long, on which vertical strings are attached, as well as by rational arrangement of ordinary strings in the middle part of the span. Double suspensions have more constant elasticity, but they are more expensive and more complex. To obtain a high rate of uniform distribution of elasticity in the span, use various ways its increase in the area of ​​the support unit (installation of spring shock absorbers and elastic rods, torsion effect from twisting the cable, etc.). In any case, when developing suspensions, it is necessary to take into account their dissipative characteristics, i.e., resistance to external mechanical loads.
The catenary is an oscillatory system, therefore, when interacting with pantographs, it can be in a state of resonance caused by the coincidence or multiple frequencies of its own oscillations and forced oscillations, determined by the speed of the pantograph along a span with a given length. If resonance phenomena occur, a noticeable deterioration in current collection may occur. The limit for current collection is the speed of propagation of mechanical waves along the suspension. If this speed is exceeded, the pantograph has to interact as if with a rigid, non-deformable system. Depending on the standardized specific tension of the suspension wires, this speed can be 320-340 km/h.
Simple and chain hangers consist of separate anchor sections. The suspension fastenings at the ends of the anchor sections can be rigid or compensated. On the main railways Mostly compensated and semi-compensated suspensions are used. In semi-compensated suspensions, compensators are only present in the contact wire; in compensated ones, they are also present in the supporting cable. Moreover, in the event of a change in the temperature of the wires (due to the passage of currents through them, changes in the ambient temperature), the sag of the supporting cable, and therefore the vertical position of the contact wires, remains unchanged. Depending on the nature of the change in the elasticity of the suspensions in the span, the sag of the contact wire is taken in the range from 0 to 70 mm. Vertical adjustment of semi-compensated suspensions is carried out so that the optimal sag of the contact wire corresponds to the average annual (for a given area) ambient temperature.
The structural height of the suspension - the distance between the supporting cable and the contact wire at the suspension points - is chosen based on technical and economic considerations, namely, taking into account the height of the supports, compliance with the current vertical dimensions of the approach of buildings, insulating distances, especially in the area of ​​artificial structures, etc.; in addition, a minimum inclination of the strings must be ensured at extreme values ​​of ambient temperature, when noticeable longitudinal movements of the contact wire relative to the supporting cable may occur. For compensated suspensions, this is possible if the support cable and contact wire are made of different materials.
To increase the service life of the contact inserts of pantographs, the contact wire is placed in a zigzag plan. Various options for hanging the support cable are possible: in the same vertical planes as the contact wire (vertical suspension), along the axis of the track (semi-oblique suspension), with zigzags opposite to the zigzags of the contact wire (oblique suspension). The vertical suspension has less wind resistance, the oblique suspension has the greatest, but it is the most difficult to install and maintain. On straight sections of the track, semi-oblique suspension is mainly used, on curved sections - vertical. In areas with particularly strong wind loads, a diamond-shaped suspension is widely used, in which two contact wires, suspended from a common supporting cable, are located at supports with opposite zigzags. In the middle parts of the spans, the wires are pulled together by rigid strips. In some suspensions, lateral stability is ensured by the use of two supporting cables, forming a kind of cable-stayed system in the horizontal plane.
Abroad, single chain suspensions are mainly used, including on high-speed sections - with spring wires, simple spaced support strings, as well as with supporting cables and contact wires with increased tension.

Contact wire

The contact wire is the most critical element of the contact suspension, directly making contact with the EPS pantographs during the current collection process. Typically, one or two contact wires are used. Two wires are usually used when collecting currents of more than 1000 A. On domestic railways. d. use contact wires with a cross-sectional area of ​​75, 100, 120, less often 150 mm2; abroad – from 65 to 194 mm2. The cross-sectional shape of the wire underwent some changes; at the beginning 20th century the cross-section profile took the form with two longitudinal grooves in the upper part - the head, which serve to secure the contact network fittings to the wire. In domestic practice, the dimensions of the head (Fig. 8.12) are the same for different cross-sectional areas; in other countries, head sizes depend on cross-sectional area. In Russia, the contact wire is marked with letters and numbers indicating the material, profile and cross-sectional area in mm2 (for example, MF-150 - shaped copper, cross-sectional area 150 mm2).

In recent years, low-alloy copper wires with additives of silver and tin, which increase the wear and heat resistance of the wire, have become widespread. Bronze copper-cadmium wires have the best wear resistance (2-2.5 times higher than copper wire), but they are more expensive than copper wires, and their electrical resistance is higher. The feasibility of using a particular wire is determined by a technical and economic calculation, taking into account specific operating conditions, in particular when solving issues of ensuring current collection on high-speed highways. Of particular interest is the bimetallic wire (Fig. 8.13), suspended mainly on the receiving and departure tracks of stations, as well as a combined steel-aluminum wire (the contact part is steel, Fig. 8.14).

During operation, contact wires wear out when collecting current. There are electrical and mechanical components of wear. To prevent wire breakage due to increased tensile stresses, the maximum wear value is normalized (for example, for a wire with a cross-sectional area of ​​100 mm, the permissible wear is 35 mm2); As wear on the wire increases, its tension is periodically reduced.
During operation, rupture of the contact wire can occur as a result of the thermal effect of electric current (arc) in the area of ​​interaction with another device, i.e., as a result of burnout of the wire. Most often, contact wire burnouts occur in the following cases: above the current collectors of a stationary EPS due to a short circuit in its high-voltage circuits; when raising or lowering the pantograph due to the flow of load current or short circuit through an electric arc; when the contact resistance between the wire and the contact inserts of the pantograph increases; presence of ice; the closure of the pantograph skid of the different-nopothecial branches of the insulating interface of the anchor sections, etc.
The main measures to prevent wire burnouts are: increasing the sensitivity and speed of protection against short-circuit currents; the use of a lock on the EPS, which prevents the pantograph from rising under load and forcibly turns it off when lowered; equipping insulating junctions of anchor sections with protective devices that help extinguish the arc in the area of ​​its possible occurrence; timely measures to prevent ice deposits on wires, etc.

Support cable

Support cable - a chain suspension wire attached to the supporting devices of the contact network. A contact wire is suspended from the supporting cable using strings - directly or through an auxiliary cable.
On domestic trains On the main tracks of lines electrified with direct current, copper wire with a cross-sectional area of ​​120 mm2 is mainly used as a supporting cable, and on the side tracks of stations, steel-copper wire (70 and 95 mm2) is used. Abroad, bronze and steel cables with a cross-section from 50 to 210 mm2 are also used on AC lines. The cable tension in a semi-compensated catenary varies depending on the ambient temperature in the range from 9 to 20 kN, in a compensated suspension depending on the type of wire - in the range of 10-30 kN.

String

A string is an element of a catenary chain, with the help of which one of its wires (usually a contact wire) is suspended from another - the supporting cable.
By design, they are distinguished: link strings, composed of two or more hingedly connected links of rigid wire; flexible strings made of flexible wire or nylon rope; hard - in the form of spacers between the wires, used much less frequently; loop - made of wire or metal strip, freely suspended on the upper wire and rigidly or hingedly fixed in the string clamps of the lower (usually contact); sliding strings attached to one of the wires and sliding along the other.
On domestic trains The most widely used are link strings made of bimetallic steel-copper wire with a diameter of 4 mm. Their disadvantage is electrical and mechanical wear in the joints of individual links. In calculations, these strings are not considered as conductive. Flexible strings made of copper or bronze stranded wire, rigidly attached to string clamps and acting as electrical connectors distributed along the contact suspension and not forming significant concentrated masses on the contact wire, which is typical for typical transverse electrical connectors used for link and other connections, do not have this drawback. non-conducting strings. Sometimes non-conductive catenary strings made of nylon rope are used, the fastening of which requires transverse electrical connectors.
Sliding strings, capable of moving along one of the wires, are used in semi-compensated catenary pendants with a low structural height, when installing sectional insulators, in places where the supporting cable is anchored on artificial structures with limited vertical dimensions and in other special conditions.
Rigid strings are usually installed only on the overhead switches of the contact network, where they act as a limiter for the rise of the contact wire of one suspension relative to the wire of the other.

Reinforcing wire

Reinforcing wire is a wire electrically connected to the contact suspension, serving to reduce the overall electrical resistance of the contact network. As a rule, the reinforcing wire is suspended on brackets on the field side of the support, less often - above the supports or on consoles near the supporting cable. The reinforcing wire is used in areas of direct and alternating current. Reducing the inductive reactance of an AC contact network depends not only on the characteristics of the wire itself, but also on its placement relative to the overhead wires.
The use of reinforcing wire is provided for at the design stage; Typically, one or more A-185 type stranded wires are used.

Electrical connector

An electrical connector is a piece of wire with conductive fittings intended for the electrical connection of overhead wires. There are transverse, longitudinal and bypass connectors. They are made from bare wires so that they do not interfere with the longitudinal movements of the catenary wires.
Transverse connectors are installed for parallel connection of all overhead wires of the same track (including reinforcing ones) and at catenary stations for several parallel tracks included in one section. Transverse connectors are mounted along the track at distances depending on the type of current and the proportion of the cross-section of the contact wires in the general cross-section of the contact wires, as well as on the operating modes of the EPS on specific traction arms. In addition, at stations, connectors are placed in the places where the EPS starts and accelerates.
Longitudinal connectors are installed on the air switches between all the wires of the catenary pendants forming this switch, in the places where the anchor sections are coupled - on both sides for non-insulating joints and on one side for insulating joints and in other places.
Bypass connectors are used in cases where it is necessary to make up for the interrupted or reduced cross-section of the catenary suspension due to the presence of intermediate anchoring of reinforcing wires or when insulators are included in the supporting cable for passage through an artificial structure.

Catenary fittings

Contact network fittings – clamps and parts for connecting overhead contact wires to each other, to supporting devices and supports. The fittings (Fig. 8.15) are divided into tension (butt clamps, end clamps, etc.), suspension (string clamps, saddles, etc.), fixing (fixing clamps, holders, ears, etc.), conductive, mechanically lightly loaded (clamps supply, connecting and transition - from copper to aluminum wires). The products included in the fittings, in accordance with their purpose and production technology (casting, cold and hot stamping, pressing, etc.), are made of malleable cast iron, steel, copper and aluminum alloys, and plastics. The technical parameters of the fittings are regulated by regulatory documents.

Page 7 of 19

The 2x25 kV AC traction network includes catenary pendants, supply wires of each track and a return rail network, which are interconnected through the windings of linear autotransformers.
Since the operating voltage of the contact wire in relation to the rails and ground with a 2 x 25 kV power supply system is 27.5 kV, standard designs with the same overall dimensions and insulation as with a conventional 25 kV AC system. Both insulated and non-insulated consoles are used, and recently, taking into account the service conditions, non-insulated consoles have become most widespread.
Based on experience in the design and operation of sections of the Moscow and Belarusian roads, the Transelectroproekt Institute has developed standard diagrams and wire suspension units for a 2x25 kV power supply system. A-185 grade aluminum wire is mainly used as the supply wire on each main track. Depending on the nature of the traction load of a particular area, wires of other brands can be used, in particular, split 2A-95.

Rice. 1.27. Layout of 2x25 kV traction network wires on supports
I - contact wire, 2 - support cable, 3 - supply wire, 4 - DPR wire

To suspend the supply wire, use standard supporting structures used to accommodate additional wires of the 25 kV AC system (feeder, suction, reinforcing, longitudinal power supply lines, etc.).

Rice. 1.28. Contact network support on a single-track section:
(designations 1-4 in the caption to Fig. 1.27; 5 - auto-locking power wire)

On a single-track section (Fig. 1.27, a), the supply wire is suspended above the DPR line on a bracket of the KFS or KF type on the field side of the support, and if this side is occupied by other wires, then above the catenary console rod (Fig. 1.28).
In this case, the DPR line is suspended from the field side on brackets such as KFD or KFDS.
On a double-track section (Fig. 1.27, b), the supply wire of this track is suspended together with one of the wires of the DPR line on a bracket of types KFDI, KFDU; in areas subject to self-oscillations of wires - KFDSI, KFDSU.
It is possible to place the supply wire of each track in the same way as on a single-track section. If the height of the support is not sufficient to maintain the permissible distances from the wires to the ground)