DSc in Engineering Science, docent Tashkent State Transport University, Uzbekistan, Tashkent
CALCULATION OF THE LENGTH OF CABLE LINES USED AT STATIONS
This article discusses the existing problems in calculating the length of cable lines at stations. It is aimed at calculating the length of cable lines at stations with new methods. The determination of the length of automatic and telemechanical control devices and common cables at stations by a new method is explained. In this case, the length of the cables at the station is reduced, it has significant economic efficiency and automatic reliability.
В данной статье рассматриваются существующие проблемы при расчете длины кабельных линий на станциях. Он направлен на расчет длины кабельных линий на станциях новыми методами. Объяснено определение длины устройств автоматического и телемеханического управления и общих тросов на станциях новым методом. В этом случае сокращается длина кабелей на станции, она имеет значительную экономическую эффективность и автоматическую надежность.
Keywords: interlocking signaling (IS), automation and telemechanics, non-combustible polyvinyl chloride (NPCH), electricity centralization (EC), transformer box (TB)
Ключевые слова: сигнализации централизации блокировка (СЦБ), автоматики и телемеханики, негорючий поливинилхлорид (НПХ), электричества централизация (ЭЦ), коробка трансформатора (КТ).
Today, the cable network installed on the electrical centralization devices serves to interconnect the centralized objects located outside the post, for example, traffic lights, arrow switches, power supply and relay transformers of rail chains, relay cabinet devices, shunting poles.
Installed cable networks can be mainly divided into three groups: traffic light, arrow and rail chain. The wires to the arrow switch, traffic light, relay and supply transformers are laid in separate cables. When designing a cable network, it is necessary to try to reduce the number of designed cables. For this purpose, when the cable is laid in long or separated sections and small stations, the wires for different purposes are combined with one cable, in addition, it is not allowed to combine the wires of the relay transformers of the rail circuit and the semi-autoblocking wires of the block mechanism with the wires of alternating current of more than 100V.
Electrical centralization cable networks of large stations with more than 100 trains per day should be designed as usual, in order to prevent the failure of the entire station link in the event of the failure of some cables, the cables of the switchgear, traffic lights, and rail chain devices are run in separate cables of even and odd directions.
Objects of the same type are grouped using distribution couplings. When grouping objects, a suitable place for installing the coupling is selected. The distribution coupling is installed where there is the object that collects the most. When grouping objects, it is necessary to make sure that there are maximum fibers of the group cable. In order to reduce the number of very small number of fiber cables that run parallel to each other in one depth, group cables should be combined in couplings, in a sequence arrangement, and group similar objects. For the same purpose, it is advisable to provide a parallel transition, in which specially installed couplings are used: two cables at a distance of 150 m are replaced by three cables at a distance of 100 m.
A group cable shall be provided with a coupler that distributes the individual cables to the post. Taking into account the length of the entry of this cable, it will not be less than 100 m, and at least three individual cables will be connected to the coupling. The number of terminals in the distributor and connecting coupling and the transformer box must take into account the fact that the fibers of the group and individual cables are connected in pieces to the same terminal. Individual cables are laid from the couplings of each object group of centralization. It is possible to connect separate cables to several objects at a distance of more than 25 m. In the cable networks of arrows and traffic lights, 3 devices in a row and, as an exception, 4 devices are allowed (for example, double arrows and EPK Electropneumatic valves, four maneuvering traffic lights). In cable networks of power supply and relay transformers, 5 object cables are allowed to be connected in series .
Polyethylene-insulated, plastic-surfaced copper wire signal blocking cables are used to connect the line of road electrical equipment in railway automation and telemechanics. In alternating current traction stations, if the length of the main cable line in the galvanically isolated supply circuit, the cable with a plastic surface exceeds the permissible cable length standard, a cable with a lead surface is used. Cables with non-flammable polyvinyl chloride (NPCH) surface are recommended for connecting the electrical circuits of alarm centralization blocking (SCB) equipment. Polyethylene layered cables are not recommended for this purpose as they do not meet fire safety requirements . Cables with plastic coating and polyethylene insulation (ГОСТ 6436-75) are designed for connection of signaling centering block (SCB) electrical circuits with a voltage of up to 380 V AC or 700 V DC and for the following characteristics: test voltage of 2000 V with a frequency of 50 Hz at a current of 5 minutes, cable electrical resistance of the insulation is not less than 5000 MOm per 1 km, the working capacity in 1 km of a pair of cables is not more than 100 nF, the working capacity in 1 km of one cable is not more than 150 nF, the current conductivity is a copper wire with a diameter of 1 mm, 1 km at a temperature of 20 ° C the resistance of the electric current conduction in the length of the cable is not more than 23.5 Ohm, the conductivity of the cable fibers should be 54.2. NPCH sheathed or sheathed cables are designed for temperatures from -40 to + 60 °C, while polyethylene sheathed or sheathed cables are designed for -50 to + 60 °C. Cable laying is carried out at an ambient air temperature of not less than 15 ° C for armored cables and 10 ° C for protective cables with plastic hoses and for other cables. During installation and assembly, the bending radius of the cables should be at least 12 diameters for the reserved and 12 diameters for the rest of the cables. The nominal thickness of the insulation of the fibers is 0.45 mm (up to 7 is allowed in 0.9 mm armored cables). The nominal thickness of the cable with a plastic surface can be from 1.5 to 2.5 mm, depending on the diameter at the base of the surface. The length of the cable being built should be at least 300 m. During laying, the entire length of construction cables is used, cable sections can be laid only at the end of the cable line .
Since 1979, the industry has mastered the production of symmetrical signal blocking, but double-burst fiber cables with enhanced electrical and mechanical properties have increased. Available cable brands are manufactured with 3, 4, 5, 7, 12, 16, 30, 33, and 42 fiber counts. The basic rules and conditions accepted for use in projects for alarm and signaling systems, as well as existing types of cable fittings in the use of symmetrical cables, are kept until new fittings are assembled. The signal blocking cables used in the construction of electrical centralization (EC differ depending on the outer diameter, description, brand, number of fibers, laying order .
Cable installation in electrical centralization (EC) devices in relay and crossover buildings, relay cabinets, control room in the control room, guard building, TB-1 and TB-2 road transformer box, RB-1 relay box, throttle transformer cable couplings, EC coupling arrow automatic cleaner in cables, UKC-12 and UKC-24 universal cable couplings, four-, seven- and eight-way distribution cable couplings. The distribution coupling has a barrier between the compartments, so any type of wire can be installed in the side holes of the coupling.
The length of the cable from the electrical centering (EC) post to the coupling or to the centralized objects is calculated according to the formulas
= 1.03 (L + 6n + + 1.5 + 1) (1),
where L is the distance from the distribution coupling or centralized objects to the post on the ordinate of the specified station plan, m; 6 – the length of the cable between the axes of a road and at the intersection of the road, m; n - the number of crossed roads; - the length of the cable to enter the post building. 1.5 - the length of the cable used to raise the cable from the lower part of the intersection m; 1 – spare cable length in the coupling, more than 50 m. m 1.03 is a coefficient that takes into account the increase of the length of the cable in the lower part of the soil by 3% (from the total length of the cable).
The length of the cable from the distribution cable to the object or between objects is calculated according to the following formula:
= 1.03 (L + 6n +2*( 1.5 + 1)) (2)
The results obtained in calculations are rounded to a number with the last digit being 0 or 5. The length of the cable is 15 m at one road crossing and 20 m at two road crossings, where traffic lights are laid on bridges and consoles (for example, to signal transformers or cable coupling). Newly installed alarm systems must have spare wires: the number of fibers is up to 10 - 1, from 10 to 20 - 2, more than 20 - 3.
The required number of wires in the cables is determined depending on the commissioning schemes of the centralization objects and the sections of the supply wires (the number of fibers in the wire). The calculation takes into account the nominal and calculated load of electrical devices and devices of signaling centralization blocking (SCB) devices, the norms of losses in the permissible wire and relay contacts in the connection .
Signaling centering block (SCB) devices supply wire cross-sections are determined by the permissible voltage drop in the mains circuit. As a rule, it is not possible to check the cross-section of wires for strengthening centralized signaling devices in signaling centering block (SCB) cables by the permissible current density, because the load calculated from the permissible voltage drop does not increase the permissible current density (the maximum permissible current density in a single copper fiber of 0.785 section with plastic insulation large load- equal to 8A). In the number of fibers in the direct and reverse supply wires of the device, the maximum permissible length of the cable is determined by the formula .
Number of fibers according to the calculation
number of fibers according to the calculation
The number of received fibers is n
number of fibers according to the calculation is
The number of received fibers is n
where : ∆U- permissible voltage drop in the cable, V; r = 0.0235 Ohm - fiber resistance in 1 m copper cable; - the current in the wire, A. and - the number of cables in the direct and reverse wires, respectively.
The maximum permissible cable length without duplication in the supply cables of the device is determined
The required cross-section of the supply wires of the device () is determined by the formula
where L is the length of the cable from the supply device to the measuring device, m; 54 - conductivity of copper,
The calculation of the number of cables in straight and reverse wires is determined according to table 1. Taking into account the effect of their different numbers on the cross-sectional size of the wires. The table is calculated taking into account that the number of straight fibers is different from the number of reverse fibers, depending on the number of the same fibers and the number of the opposite.
For cables not listed in the table, the amount of fibers can be determined by formulas
Voltage drop in the cable,
In conclusion, on the basis of a new mathematical method of determining the length of cables in railway stations, by automating automatic and telemechanical control devices, the cost of cables and the human factor are reduced, the length of common cables is reduced by new methods, and economic efficiency is achieved. By determining the length of obsolete cables in stations, using a wireless microprocessor method, a significant increase in the work of receiving and sending trains at the station is achieved.
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