Master thesis in communication engineering 1
Discussion on construction control of subway communication power supply system
Metro communication power supply system is a necessary condition to ensure the normal operation of the communication system, and the communication power supply system must be safe and reliable. This paper analyzes the composition of subway communication power supply system and discusses its construction control measures.
Keywords subway communication; UPS battery
I. Composition of Metro Communication Power System
Subway communication power supply system consists of AC automatic switching power distribution cabinet, UPS, high-frequency switching power supply, battery pack, power supply monitoring, computer room environment monitoring and other subsystems. The construction of subway power supply system should ensure that the system can supply power to all subsystems and equipment safely and reliably, and has the functions of lightning protection, overvoltage protection and output short circuit protection.
* * * A * * AC self-cutting power distribution cabinet
AC self-cutting power distribution cabinet is mainly used for the conversion and distribution of AC power supply. The AC self-cutting power distribution cabinet automatically/manually switches two external AC power supplies through the modular two-way power supply automatic switching device, which has reliable electrical and mechanical interlocking function and has a delay device, and the delay can be adjusted from 0 to 30 seconds. The multi-load shunt of AC distribution cabinet distributes the output power and outputs it to all communication subsystem equipment. The LCD screen is installed on the AC distribution cabinet, which can display the three-phase voltage, load current and alarm information of the power supply. The distribution cabinet has overvoltage, undervoltage, overcurrent, lightning protection and surge absorption protection devices. At the same time, the AC power distribution cabinet has the function of self-diagnosis, giving out an audible and visual alarm when the power supply fails, and providing a communication interface for local and remote monitoring.
* * * Two ***UPS
Metro communication power supply generally adopts static online UPS, which consists of rectifier, inverter, static switch, automatic/manual bypass switch and monitoring module. The safety control of UPS includes voltage surge suppression, low voltage boost and battery life protection.
* * * Three * * DC high-frequency switching power supply
DC high-frequency switching power supply consists of rectifier module, monitoring module and DC distribution unit. Like UPS power supply, DC high-frequency switching power supply comes with a battery pack to ensure that the battery can provide energy for a certain period of time when AC power supply fails.
* * * Four storage batteries
At present, the subway communication basically adopts valve-controlled fully sealed maintenance-free lead-acid batteries. Generally, closed batteries are equipped with safety valves and acid-proof tablets, which can automatically adjust the internal pressure of the battery. Acid-proof sheet has the function of resisting liquid and explosion, and its safety lies in ensuring the capacity and life of battery.
* * * Five * * * Monitoring System
Because the communication power room is unattended, in order to facilitate management, some urban subways combine track monitoring and power supply with environmental monitoring, and set up a * * * * station environmental monitoring system, which is centralized monitored by the control center. It mainly monitors low-voltage distribution cabinets, UPS output parameters, room air conditioning, temperature, humidity, flood, access control, illegal intrusion, etc.
Second, the subway communication power supply system construction control
* * * A * * AC self-cutting power distribution cabinet structure
1. Installation of equipment foundation
Every 1 m, plant a foundation support on the ground on both sides of the installation position of the foundation channel steel. The solder joints and foundation supports shall be painted with antirust paint once, and then with zinc-rich paint twice. For the equipment room of underground station with high humidity, the welding spot and foundation support of channel steel foundation should be coated with a layer of sealing paint in addition to clothing treatment.
Step 2 put the cupboard away
The guide wheel of the electromagnetic device is used for installation. The electromagnetic power supply is 18V DC battery; Core diameter 2cm conductor section 1.5mm? ; Four universal wheels. The iron core is wrapped with wires, painted and fixed on universal wheels, and every two universal wheels are connected to the power supply as a group. Two groups of electromagnetic guide wheels are fixed at the bottom of the device respectively, and the power supply is connected, so that the guide wheels and the device are fixed and reliable. Laying a springboard in front of the foundation channel steel, pushing and pulling the device to the installation position, and adjusting the device according to the distance requirements of the construction design drawings. After the adjustment is completed, disconnect the power supply of the two groups of guide wheels in turn to complete the positioning of the cabinet. After the cabinet is completely in place, use 1000V insulation resistance meter to test the insulation of the cabinet. The minimum insulation resistance is not less than 2mΩ.
3. Bus bar installation and cabinet fixing
When connecting the bus, use a brush to remove the oxide film on the surface of the bus to be connected; Use a torque wrench to lock the bush nut with a torque of 40Nm.
Cabinet fixing is divided into two parts: cabinet fixing and cabinet and foundation fixing. Among them, the fixing of cabinet and foundation is the main operation content of cabinet fixing. First, fix the cabinet with the foundation, find the ribs of the foundation channel steel at the four corners inside the equipment, and install the fixed pressure plate of the power distribution cabinet on it. Then, using the pressure plate as the mold, four ∮ 10.5 were drilled on the insulating plate and the channel steel respectively. Finally, tap the existing hole with a tapping bit, and clean the iron filings left by drilling and tapping with a vacuum cleaner. After the above procedures are completed, put nylon sleeves and insulating pressure plates on the mounting bolts to fixedly install the cabinet.
4. Installation insulation treatment
After the installation of the cabinet is completed, the interior of the power distribution cabinet is cleaned for the second time with a vacuum cleaner, and the metal chips, iron chips and dust left over from the construction are taken as the key cleaning objects. After cleaning, remove the protective film on the upper surface of the insulation board, and then use anhydrous alcohol to clean the insulation board for the second time. Finally, use 1000V insulation resistance meter to test the insulation of the cabinet. The minimum insulation resistance is not less than 2mΩ.
* * * Two * * UPS structures
According to the different capacity selection and type selection of UPS equipment, the volume and weight of UPS are also very different. Take 100kVA UPS with power frequency machine as an example. Because there are input and output isolation transformers in UPS, the equipment weight of UPS is about 1 ton, and the outer packaging is about 1.2 ton. The overall dimensions of the device are about 0.9 meters wide, 0.9 meters deep and 2 meters high. According to the principle that the centralized UPS system should be set as close as possible to the load center, in general, the computer room of the system should be set on the station hall floor, and such large and heavy equipment should be set on the station hall floor, so we have to focus on the related problems in the transportation process. In the process of project implementation, we should first pay attention to the transportation path of equipment, and decide whether it is necessary to set lifting holes according to the situation of the station building. If hoisting holes are set, it is necessary to pay special attention to the coordination between the arrival time of equipment and the civil construction period, so as to avoid the situation that the civil hoisting holes have been blocked when the equipment arrives at the site. If the equipment is transported from the export, attention should be paid to the width of the relevant access door and the access opening itself in the design process to ensure the transportation requirements; Secondly, we should pay special attention to the choice of transportation mode and the personal safety of transportation personnel during transportation, especially when going down stairs to prevent equipment from falling and causing safety accidents.
About incoming cables and feeder cables. For example, the centralized UPS system selects UPS with UPS capacity of 100kVA or above. Because the incoming cable is thick, if the cable enters from under the overhead floor, the height of the overhead floor is generally less than 300mm, which cannot meet the requirements of the cable turning radius. If the height of the raised floor is increased, the upper space of the room will be more tense. At the same time, the height of the floor will increase, which will also increase the number of steps at the door and occupy the room area. Therefore, it is suggested that UPS incoming line should adopt incoming line mode. The feeder cable can be put up or down in theory because of its small cross section, but considering the convenience of cable lead-out, it is suggested to put it down.
When coordinating the integrated pipeline, it should be ensured that the air outlet between the equipment is not above the equipment, otherwise it will affect the safe use of the equipment and even fail to pass the acceptance. Therefore, in the process of civil engineering cooperation, the equipment should be arranged relatively accurately, so as to reduce the workload in the cooperation of comprehensive pipelines. As the centralized UPS system generally provides two power sources for each power load, in order to ensure the reliability of the distribution cable and reduce other faults affecting the normal execution of the weak current system on the cable channel, if conditions permit, the two cables should take different paths to reach the distribution box of each system.
* * * Install three * * * battery packs.
Do a good job in battery appearance inspection: the nameplate and certificate are clear and up to standard. The production date, brand and capacity of the battery meet the requirements. Model, specification and flame retardant efficiency meet the design requirements. Battery slots, covers and other materials are flame retardant. The battery number is correct and the paste is neat and firm. Positive and negative polarities are correct, and polarity and terminals are clearly marked. ? The battery is clean, dry and free of stains. The shell has no crack, good sealing and no deformation. The pole is free from deformation, damage or corrosion. Exhaust valve parts are complete, no damage, no acid mist escape.
The battery rack spacing meets the design requirements, which is convenient for battery installation, maintenance and measurement. No more than two rows of batteries shall be installed on each floor. The battery rack shall be firm and reliable, and shall not be sunken or deformed. The battery rack is free from damage and corrosion. Reliable access to the grounding grid should have rust prevention measures and obvious signs. The battery is installed smoothly, evenly and neatly. The shorter the distance between the battery pack and the power supply, the shorter the interlayer connection line and output line.
Oil-based anti-embroidery grease is not recommended for bolts, bolts, plane gaskets and sampling ports. In the battery connection part. Terminals and clamps shall use qualified parts, and lead-free brass taper clamps shall not be used, and gaskets shall not be added between battery poles and terminals. Standard multi-strand flexible wires with flame retardancy, voltage resistance of 450V, acid resistance and high temperature resistance above 70℃ should be used for interlayer connection, and the wire diameter should match the battery capacity. The battery connecting wire should use the battery manufacturer's special wires and connectors. There is a gap of not less than 15mm between batteries. The battery interlayer height shall not be less than150 mm. When connected in parallel, the cable length from each battery group to the load should be equal. It is not recommended to use battery packs in parallel, and it should be within two groups as far as possible. Batteries of different capacities, brands and manufacturers shall not be connected in parallel, and the production batch of parallel batteries shall be limited to half a year.
References:
[1] sheets. UPS Power System Application Manual [M]. Beijing: Electronic Industry Press, 20 12.
Master thesis of communication engineering II
Discussion on the application of optical fiber communication technology in power system
Abstract: Power system is one of the most basic energy supply structures in China, and it is also the most extensive continuous energy supply network. By 20 10, the length of 330kv and above lines in China will reach 95 1000 km, and it is estimated that the length of the new power grid will be 13200 km during the Twelfth Five-Year Plan period. The huge power system not only promotes the development of new energy sources such as wind energy, hydropower and solar energy, but also forms a large-scale power system communication network. This paper introduces the application of optical fiber communication in power system, expounds the functions and characteristics of different application levels, and puts forward some suggestions on the rational construction of modern power grid system communication.
Keywords: optical fiber communication; Electric power system; Electric power communication network; App application
From the perspective of communication network, the communication network of power system is one of the larger private networks in China at present. It undertakes all voice, data, video and broadband services of the power system, including conventional telecom services, internal calls and office automation services. Generally speaking, the communication network of power system, like transmission network, is indispensable and very important, and its integrity and stability will directly affect the safety of power supply system.
In fact, optical fiber communication technology has surpassed its own business and become the most advanced comprehensive technology in recent decades. Combined with the power system's own needs, it can provide rapid monitoring, fault location, remote monitoring and other functions for the power grid system, and become the main auxiliary part of the application layer of China's power grid system. Judging from the above functions, optical fiber communication mainly attacks power grid automation control and communication platform in its scope of action, and its objects mainly include master station system, substation system and feeder terminal.
First, the application in power system automation
Power system is an important part of China's economic development and social progress. Because of China's vast territory and uneven distribution of energy and technology in the east and west, a large number of long-distance transmission lines need to be set up, thus forming a complex power grid system. According to the analysis of the actual situation, we should not only ensure high efficiency and economy, but also minimize the line loss during transportation. From the point of view of network operation, a large number of relay signal transmitting, receiving and responding devices have become the most important solution.
The power communication network formed on this basis mainly includes three aspects, namely, communication station, transfer station and dispatching department. These departments are connected with each other through a dedicated optical fiber local area network, which is a part of the electric power professional network. In order to realize the stability and security of interconnection, it is necessary to consider the interference of communication network by electromagnetic field, which was very common in the past and the maintenance cost remained high. And optical fiber communication technology can solve this problem well.
The diameter of ordinary optical fiber is between 3 mm and 9 mm, which belongs to single-mode optical fiber, and the maximum diameter of multimode optical fiber is also below 50 mm unit; The good expansibility and integration of optical fiber communication technology make it one of the important means of modern communication in a short time and play an important role in the application of power system. In terms of optical communication technology, optical fiber communication technology is favored mainly because of its own advantages, including: good anti-interference, large capacity, long transmission distance, small volume, light weight, long life, environmental protection and low consumption.
In the power system, it can be divided by superiors and subordinates to reflect different control rights. Generally speaking, the size of the power grid determines its position in the power grid system. The extra-large main station floor can be divided into two floors: central main station and regional station. The communication between the main station layer and the sub-station layer requires reliability and security, so optical fiber communication technology is generally adopted.
Analysis on the characteristics of automatic communication in a * * * power system.
Power system automation is a key project in China in recent years. The reason why optical fiber communication can become one of the infrastructure of power grid communication is that it conforms to the characteristics of monitoring, detection and isolation. While building communication facilities, the first thing to consider is the current situation of power grid construction. The State Grid covers most of the densely populated areas in China, and the power stations are distributed in points, facing a variety of natural and geographical environments.
The characteristics of China's power grid are that there are many collection points, but the scale is small and there are few effective data, so it is impossible to set up special devices to set up a communication room, and at the same time it needs manpower and material resources to perform its duties; In this case, the construction of power system automation is particularly important, and the realization of power system automation has very urgent requirements for communication modules.
The complexity of the environment means that the communication module must withstand harsh weather and natural conditions, and cooperate with the realization of power system automation function, which puts forward higher requirements for its function and composition, such as lightning protection and corrosion protection. In the past, communication modules such as twisted pair and power carrier, which were widely used in communication modules, were very vulnerable to damage and interference, and lacked effective solutions in solving geographical faults.
* * * Design of communication network of power system
It is an indisputable fact that the foundation of power system automation is a fast and reliable communication network. Optical fiber communication technology, combined with fast Ethernet topology mode and advanced virtual bus control technology, can realize massive terminal information collection, rapid traversal and detection of power grid system.
Structurally speaking, the control platform of virtual bus mainly sends instructions to the following direct nodes. In order to minimize the delay, with the help of optical fiber communication network and intelligent technology, it can be directly controlled under the setting of high authority. However, it is not recommended in practice, because leapfrog management may cause repeated transmission of system instructions, which is not conducive to the maintenance of external communication equipment. An effective early warning mechanism can be established, such as an alarm device and a forced reminder device. In the process of networking, we should give full consideration to the problem of many automatic design nodes, send instructions in batches at the same level, and select the franchise mechanism in a short time by establishing a data model to cope with the changing external power environment.
In addition, it is worth mentioning lightning protection measures. The communication module working with the electric power automation system is located outdoors. Although the optical fiber communication line has a good protective layer, there is still the risk of network disconnection when it is squeezed by a large external force.
Second, the application of distribution network communication platform
During the "Twelfth Five-Year Plan" period, China put forward the construction plan of "smart grid", and State Grid Corporation indicated that it would comprehensively strengthen the construction and promotion of "smart grid" in order to realize the automation of distribution network. Using computer technology, network technology and electrical automation technology, a complete power automation system can be built, and the communication platform is very important in the whole distribution network.
However, the communication mode of distribution network is completely different from that of substation. As far as the structure is concerned, it should be divided according to the actual working environment, which leads to complex topological structure, scattered group points and many communication points. In the past work, the communication facilities of distribution network were mostly built by cables, but the effect was not ideal. So far, the defect of poor signal transmission by cable has not been solved; In wireless communication technology, although the problem of geographical limitation can be solved, there is still a problem of poor signal reception, and the cost of wireless communication is much higher. Combining these two situations, optical fiber communication technology can perfectly solve their defects and is the best choice for the communication platform of distribution network.
* * * * Analysis of Optical Fiber Communication Network Architecture in Distribution Network
The laying of optical cables is consistent with the laying of power cables in the distribution network. On the one hand, it can reduce the extra expenses caused by repeated construction, on the other hand, it can ensure the close cooperation between the two, and it is also convenient for later maintenance and management. However, the regional construction of optical fiber is related to the communication topology, rather than a simple geographical relationship.
At present, there are two common communication architectures.
Firstly, P2P*** peer-to-peer network architecture is adopted.
Two substations with the same power transmit electricity to an area, and they are in a ring structure, so the efficiency is relatively stable. The biggest advantage of this structure is the protection of power supply and network at the same time. Unless both power stations in the ring structure lose their functions, the nodes in the intermediate link will lose their communication functions. But the probability of this happening is very small.
Second, the single power tree structure is adopted.
For areas with less electricity consumption, this method can be used to give full play to the advantages of long-distance optical fiber communication. In the process of realizing the automation of distribution network, the network communication part is used more frequently.
Advantages of * * * two * * optical fiber communication in distribution network
The distribution network serves many clients, including cities and industrial areas in high-quality electricity-consuming areas, as well as vast rural areas, involving high, medium and low distribution levels, and the task is very heavy. In addition to safety and stability, it is more important to realize the function of monitoring and judging faults.
There are many kinds of optical fiber products with different efficiencies. There are mainly two kinds of optical fibers used in the actual power system: ** 1*** overhead ground optical fiber. This kind of optical fiber product is designed with thermal insulation layer, which is made of thermoplastic and can play the greatest protection role. The laser welding technology used to extend the stainless steel pipeline to a distance of more than 10,000 meters can effectively prevent lightning damage. * * * 2 * * All-dielectric self-supporting optical cable. This kind of optical cable is light in weight, and has good lightning protection performance and electromagnetic interference resistance.
In the long run, the communication module of distribution network must meet the demand that the failure rate is lower than that of power system, otherwise it will be regarded as putting the cart before the horse, adding extra burden to power system. In view of the equality of power cable laying and communication cable laying in construction, it is very important to choose high-quality and efficient communication materials and technologies. The basic substances of optical fiber communication are optical fiber, light source and optical detector, which have high stability in terms of the structure and characteristics of optical cable, and the external humidity, corrosion and lightning strike have little influence on it, so it has strong advantages.
Three. Concluding remarks
At present, China is in the critical stage of the 12th Five-Year Plan. The improvement and progress of the power system will further promote the economic and social modernization of China. According to the information released by the Ministry of Industry and Information Technology, during the Twelfth Five-Year Plan period, the investment scale of China's optical fiber infrastructure will reach 500 billion yuan. The application scope of optical fiber material technology and optical fiber communication technology will expand with the development of time. As an important part of power system, the application of optical fiber communication equipment and technology is still developing. It is believed that with the progress of science and technology and the research of new materials, optical fiber products will gradually show diversified characteristics and play a more important role in the power system.
References:
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