Current status and development of railway communication power supply

Railway communication power supply is the "heart" of the railway communication equipment industry. It is an indispensable component of various communication means and has an important impact on ensuring communication quality, because the failure of communication equipment is local, and the failure of communication power supply will have a greater impact. Failure of the railway communication system will not only affect official communications, but more seriously, it will affect train operation and cause heavy losses to the national economy. Therefore, railway communication power supplies have always received the attention of relevant departments. The Ministry of Railways has successively formulated technical requirements and related design specifications for communication power supplies, and strengthened technical management; systems and equipment have been continuously improved and improved with the advancement of technology. Railway communication power supplies are now The power system and features are introduced below.

The railway communication power supply is an independent power supply system, consisting of an external AC power supply system and a DC power supply system. The external AC power supply consists of two parts: one is the external AC power supply from the railway area substation, power distribution station, railway dedicated line power supply, power through-line power supply, automatic blocking power line power supply and local power supply; the other is the external AC power supply. The second refers to self-provided power generation.

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Along the railway, 10KV power distribution stations are set up every 40-60km, which are used to supply power to automatic blocking power lines and power through lines.

It is impossible to build power through lines on main railway lines and branch lines with heavy traffic; in addition to power through lines in automatic blocking sections, automatic blocking power lines are also built. The automatic blocking power line is a special power supply for the automatic blocking signaling equipment of the railway, and the communication equipment of the railway intermediate station is also powered by it.

The power through-line is the main power supply for small-capacity loads related to traffic at stations along the line, and is a backup power supply for automatic blocking lines.

Railway communication network communication equipment at sub-hubs and above are classified as first-level loads; the power supply room below the sub-hub and the communication machinery room of intermediate stations are classified as second-level loads.

The power supply standard for the primary load is: one power supply from two different substations or two power supplies from different busbar sections. Therefore, communication equipment at the sub-hub and above is powered by two reliable AC power supplies; below the sub-hub is powered by one reliable AC power supply. When there is a second AC power supply nearby, two AC power supplies are used.

The self-provided power supply for railway communications generally uses oil engine generator sets. For areas that meet sunshine requirements or wind speed requirements, using solar or wind power development power as a backup power supply is also a feasible solution, but its one-time investment is relatively high.

Self-provided AC generator sets, with the advancement of technology, currently use equipment with automatic input, automatic withdrawal, and automatic replenishment. In addition, they must have standardized interfaces and communication protocols to complete their remote signaling, telemetry, and remote control functions. Achieve the purpose of maintenance by few people and no one on duty.

The setting up of self-provided generating sets is the only reliable measure to ensure uninterrupted power supply to communication equipment, especially for failures caused by disasters, the interruption time of which is difficult to determine. Therefore, railway communication stations are required to be equipped with self-prepared generator sets; the communication machinery room of intermediate stations is equipped with a mobile generator set for every 2-4 stations. In the event of a fault, it will be carried by the communication work area to the fault location for use to ensure the reliability of power supply. Co-location can reduce the backup time of the battery pack, thereby reducing the battery capacity.

The capacity of the self-provided alternating current generator set shall meet the AC power for communication equipment, the floating charging power of DC power supply, the charging power of the battery pack, and the guaranteed electrical power that should be provided in the main room of the communication station.

Guaranteed lighting is generally calculated based on actual conditions. When there is no data, except for the lighting of the main computer room, the lighting power of other houses can be estimated based on 30%-50% of it.

The reliability of the power supply system is composed of the reliability of the AC power supply system and the DC power supply system. Research data shows that the reliability of the AC power supply system accounts for 65% of the total system reliability index. Therefore, improving the reliability of the AC power supply is the most important.

The DC power supply system of railway communication power supply consists of rectifier equipment, DC power distribution equipment and battery packs. The power supply method adopts DC centralized power supply and continuous float charging. The rectifier equipment and the battery pack are float-charged day and night to supply the DC power supply to the communication equipment, and at the same time, the supplementary charging current for the self-discharge of the battery pack is provided. Using this power supply system, the battery pack has high efficiency, long life and strong reliability, so it is the preferred power supply method. The basic voltage of railway DC power supply is set at -48V. Other types of voltage: such as -12V, -6V, -24V, etc. or AC 220V. When the load is small, it can be obtained through a converter or inverter. Extra large communication hubs (generally, the switching system capacity can be greater than 50,000 doors). The decentralized power supply method has the advantages of reducing the voltage drop of the power line and reducing the impact of faults. As the railway communication network goes to the market and large-capacity communication hubs will increase, the decentralized power supply method will be more adopted.

Rectifier equipment using high-frequency switching technology has the advantages of small size, light weight, modular structure, easy expansion, high efficiency, high power factor, allowing input AC voltage to vary widely, high voltage stabilization accuracy, and low noise. It has been It has been widely used in railway communication power supply systems to replace phase-controlled power supply.

Valve-regulated sealed batteries have the advantages of small size, large specific energy, less pollution, easy use and maintenance, can be stacked horizontally, can be placed in the same room with communication equipment, and save engineering investment. They have been designated for use in communication power systems. preferred battery. Among them, the liquid-poor battery is more advantageous because of its small internal resistance and good product consistency and uniformity.

The low-voltage constant voltage charging method for battery packs has been widely used internationally and domestically. Its advantages are that it can extend the service life of the battery, improve the quality of power supply, and simplify direct power lines. The Ministry of Railways has implemented a low-voltage constant-voltage float charging system for power supply. Its principle and maintenance are basically the same as the "continuous float charging system". The difference is that the float charge voltage is increased from the original (2.18±0.02) V to 2.3V. After the external AC power supply fails, the battery is discharged; after the AC power is restored, the "online" voltage is still used at the terminal voltage of each battery of 2.3V. "Style" float charging, that is, charging with load. Its advantage is to extend the service life of the battery without losing power, and has the advantages of simplified operation, easy maintenance, and improved power supply quality.

Recently, new high-energy valve-regulated batteries (also known as lead cloth batteries) have attracted attention in the industry. It is an improved battery developed on the basis of the original valve-regulated battery. Its working principle is the same as that of the valve-regulated battery.

The key technology lies in the use of new battery materials, advanced battery structures and new production processes.

It mainly includes the following aspects:

1. The coaxial composite lead wire textile mesh produced by a special process is used as a grid, which replaces the gravity-cast metal grid in traditional batteries;

2. Apply positive lead paste and negative lead paste on the same screen, and connect them with an uncoated screen to form a bipolar plate;

3. Bipolar plates are staggered and stacked to form different pole groups according to different voltage and capacity requirements, eliminating the need for connections between single cells;

4. The pole group is compressed with a squirrel cage to form a tight assembly;

The 5-pole plate is placed horizontally;

6. Add an appropriate amount of oxidizer and other additives to the lead paste on the coating board;

7 Eliminate the curing and drying processes in traditional battery production processes

8. The battery adopts internal formation, eliminating the formation process of the traditional battery production process;

After adopting the above new materials, new structures and new processes, the new high-energy valve-controlled battery has the following superior properties:

1. High discharge power and faster charging.

Due to the change in structure, multiple longitudinal parallel lead wires are used to connect the current, which reduces the internal resistance of the battery and enables faster charging. Generally, it takes about 30 hours for a valve-controlled battery to be fully discharged after 100% deep discharge, while lead cloth batteries require About 4 hours.

2 Long cycle life

Since the grid of the lead cloth battery is woven from coaxial lead wire, the inner core of the coaxial lead wire is made of multi-glass fiber, so it is strong and does not need to add other metals to the lead of the cast grid, thus preventing Grid corrosion caused by the addition of other metals. Lead cloth batteries use high-purity decomposed lead, which greatly extends the life of the battery.

3 light weight

Compared with the traditional grid, the amount of lead used in the lead cloth woven with coaxial lead wire as the inner core of glass fiber is reduced by more than 67%. Taking into account other structural improvements, the weight is reduced by 25-50%. Energy to weight ratio increased by 50%.

4 The performance is more reliable and balanced. The elimination of curing, drying and formation processes simplifies the production process and makes automated assembly easier, making product performance more balanced and reliable.

In addition, it also has the advantages of higher security and less maintenance.

In recent years, with the application of optical cable digital communication systems and digital add-drop equipment in railway intermediate stations, new requirements have been put forward for communication power supplies. There are many intermediate railway stations, most of which are scattered in remote areas. Their AC voltage fluctuates widely and the power supply quality is poor. The fluctuation range of AC 220V at the location is as high as plus or minus 30%. Power outages are frequent and maintenance technical strength is weak. In order to meet the requirements of railway communication, it must be modified.

First, the AC power supply uses the dynamic blocking power supply as the main source and the power through-line as the backup, which improves the reliability of the AC power supply and improves the quality of the AC power supply. Then the power supply cabinet for railway intermediate stations was developed to provide power for communication equipment.

The railway intermediate station communication power cabinet consists of an AC power distribution unit, a DC power distribution unit, a high-frequency switching rectifier module and a valve-regulated lead-acid battery pack. The capacity of the rectifier module is generally 5A, 10A, or 16A, and it operates in a load sharing mode of one main and one backup, or 2 main and 1 backup. The battery pack is generally 100AH. The above equipment is integrated in a cabinet and uses DC-48 to power the communication equipment of the intermediate station.

Taking into account the unpredictability of the time between two AC power outages, someone is required to be on duty after the AC power outage, and maintenance personnel in the work area bring the mobile generator set to the site for maintenance within 8 hours. The low voltage pre-alarm value of the battery pack can be set according to the arrival time of maintenance personnel, and can automatically send out visible and audible alarm signals.

Practice over the past few years has proven that this kind of railway intermediate station power supply cabinet meets the needs of intermediate station communication equipment. There are already finalized products from on-road and off-road manufacturers, which have been put into use after network access testing.

To sum up, in the past ten years, high-frequency switching power supplies have been used to replace phase-controlled power supplies, valve-regulated sealed lead-acid batteries have been used to replace acid-proof batteries, and computer centralized monitoring has been used to replace manual control. This is the current development trend of communication power supplies. The railway communication power supply system continues to incorporate new technologies and products from the aspects of system, specification, maintenance, and product standards, laying the foundation for railway communication. With the reform of the railway communication management system, Tietong Network will become a communication network for on-road and off-road operation services, and will put forward higher requirements for communication power supply to meet the needs of railway communications going to the market.