Intelligent low power engineering comprehensive wiring system essence knowledge summary
preface:
1. To confirm the cable tension
When the cable has surplus at two terminals, it shall be cut according to the required length instead of being rolled up and tied up. The distance of the anti winding section at the joint of the cable shall not exceed 2 cm. Too long will cause large near end crosstalk. During the authentication test, next near end crosstalk cannot pass. At the joint, the outer protective layer of the cable needs to be pressed in the joint rather than outside the joint. Because when the cable is subjected to external tension, the stress is the whole cable, otherwise the stress is the metal part connected between the cable and the connector, which will make the termination between the connector and the module unstable. During cable wiring construction, the cable tension is limited to a certain extent, generally about 9 kg. Please confirm the tension with the cable supplier. Excessive tension will damage the symmetry of the cable pair.
2. Thread laying skills should be standardized
When making a line, some construction workers do not follow 568a or 568B marking skills, but match white and orange for line 1 and line 2, white and green for line 3 and line 4, white and blue for line 5 and line 6, and white and brown for line 7 and line 8. Such a line can ensure smooth line during construction, However, its line index is very poor, especially the near end crosstalk index, which will lead to serious signal leakage, difficulty in accessing the Internet and indirect interruption. Therefore, the project manager must remind the production workers not to make such mistakes.
3. Anti interference scheme
In the generic cabling system, steel pipes shall be used for horizontal cables as much as possible, and bridges shall be used for the laying of main cables as much as possible. Then, in the process of construction, the grounding bridging between steel pipes, between steel pipes and bridges, and between bridges and bridges shall be done well. For such pipelines, we lay unshielded cables and large pairs of cables, which can play an effective shielding role, reduce the impact of external interference on the signal transmission of generic cabling system, and make up for the shortcomings of unshielded cabling system.
4. The trunking shall preferably be installed in the ceiling
When installing trunking, multiple considerations shall be taken to install the trunking in the ceiling of the corridor as far as possible, and the branch pipes to each room shall be properly concentrated near the manhole for maintenance. The centralized wiring construction should be carried out in front of the corridor ceiling, which not only reduces the wiring hours, but also helps to protect the worn cables and does not affect the decoration in the room. Generally, the corridor is in the middle, and the average distance of wiring is the shortest, so as to save cable costs, improve the performance of generic cabling (the shorter the line, the higher the transmission quality), and try to avoid the trunking entering the room. Otherwise, it will not only cost the line, but also affect the room decoration and is not conducive to future maintenance.
5. Distinguish the line sequence of large logarithm cables
In the actual construction, we often encounter the connection problem of 25 pairs or 100 pairs of large pairs of cables, which is not easy to distinguish. Here, we make simple parameters for you. Take 25 pairs of cables as an example. The cable has five basic colors, in the order of white, red, black, yellow and purple. Each basic color includes five color sequences, namely blue, orange, green, brown and gray. That is, the order of 1 ~ 25 pairs of all line pairs is white blue, white orange, white green, white brown, white gray... Purple blue, purple orange, purple green, purple brown and purple gray.
For 100 pairs of cables, take 25 pairs of cables as an example. The 100 pairs of cables are divided into four 25 pairs with blue, orange, green and brown ribbons. Each group is wound around each other in the above way, and we can distinguish 100 pairs. In this way, we can play on the terminals of 110 distribution frame one by one. As long as the same general wiring sequence is adopted in the management room and equipment room, and then the cable identification is done well, it can be easily used to transmit the telephone.
1. System structure design
The general building wiring system adopts the hybrid scheme of optical fiber UTP copper cable. Considering the structure of the building group and the longest distance supported by multi-mode optical cable and twisted pair, a computer center room is set up, and one building wiring room is set up in other buildings. The data backbone system between the building distribution room and the building distribution room is connected by six core outdoor multimode optical cable, which can support a variety of applications from traditional Ethernet, token ring network, 100MB / s Fast Ethernet, FDDI, 622Mb / s ATM, Gigabit high-speed Ethernet, etc. the horizontal subsystem wiring adopts category 5 unshielded twisted pair, which can support up to 622Mbps ATM and 550MHz bandwidth image applications, It can more effectively reduce crosstalk interference and make voice, data and image transmission clearer and more effective.
2. Workspace subsystem
The work area subsystem provides users with a standard information outlet meeting high-speed data transmission, and realizes the matching and connection between the information port and the equipment terminal. This part mainly includes non active devices such as jumpers and flexible cords. The data part adopts (rj45-rj45) super class 5 crimping jumpers. Each information socket shall support the following terminal equipment: data communication, voice communication, image transmission, etc.
3. Horizontal subsystem
The horizontal (wiring) subsystem consists of information socket, cable or optical cable from information socket to floor wiring equipment, floor wiring equipment and jumper. Information sockets are RJ-45 standard. The length of each data horizontal twisted pair shall not exceed 90m. The horizontal twisted pair wiring is led out from the information points in the room and distributed to the corresponding building distribution cabinet. The whole wiring is connected in star topology. PVC trunking is used for installation.
4. Management subsystem
The management shall mark and record the distribution equipment, cables, information sockets and other facilities in the equipment room, junction room and work area according to a certain mode, and comply with the following provisions:
1) The large-scale wiring system should be managed by computer, and the simple wiring system should be managed according to the drawings, and the records should be accurate, updated in time and easy to consult.
2) Each cable, optical cable, distribution equipment, termination point, installation channel and installation space shall be given a unique mark.
3) Wiring equipment, cables, information sockets and other hardware shall be provided with signs that are not easy to fall off and wear, and detailed written records and drawings shall be provided.
4) Both ends of cables and optical cables shall be marked with the same number.
5. Equipment room subsystem
The main equipment room (computer center room) of the whole building is mainly equipped with main distribution cabinet, network server, switch and other network equipment. Considering the height and width of the building, distribution line rooms are set up between floors. In order to ensure the safety and reliability of the system, all wiring equipment and network equipment must be placed in the cabinet.
Environmental requirements for equipment room (machine room):
1) Temperature and humidity requirements
According to the temperature and humidity requirements of relevant equipment and devices of generic cabling system, the safety of equipment room shall be class B. That is, the temperature is 12 ~ 30 ℃, the relative humidity is 35% ~ 70%, and the temperature change rate is less than 10 ℃ / hour.
2) Requirements for heat insulation, dust prevention, fire prevention and anti-static
These factors will have a serious impact on the performance and safety of the computer system. In order to make the system operate safely and reliably, the selection of decoration materials and construction technology of the computer room should be considered. It is recommended that the floor should be anti-static raised floor, the wall should be fireproof coating or metal plastic aluminum plate, and the ceiling should be metal ceiling.
3) Lighting requirements
The equipment room shall be 0.8m away from the ground, and the illumination shall not be less than 200lx.
4) Power supply and distribution requirements
The power supply in the equipment room shall meet the following requirements: frequency: 50Hz; Voltage: 380V / 220V; Independent power supply is recommended.
6. (vertical) trunk subsystem
Trunk system refers to the cable from the main distribution room to the floor distribution room. The generic cabling system does not have another floor distribution room, so the design of vertical trunk subsystem is not considered.
7. Building complex subsystem
The complex subsystem extends cables from one building to communication equipment and devices in other buildings of the complex. It is a part of the whole cabling system (including transmission medium) and supports the hardware required to provide communication facilities between buildings, including copper wire, optical cable, etc.
8. Building requirements for machine room
1) Clear height of house: 3.0m.
2) The floor adopts movable anti-static floor (600x600mm), which is 300mm above the ground.
3) T-shaped open aluminum alloy keel frame and microporous aluminum ceiling (600x600mm) are adopted for the roof. The ceiling height is 3.0m from the movable anti-static floor.
4) The fresh air supply and exhaust of the central machine room adopts the mode of ventilator. The installation height of the reserved ventilation fan hole is 3.5m above the ground.
9. Working environment requirements of computer room
1) Requirements for temperature, humidity and dust concentration in air
When starting up, the temperature and humidity in the machine room shall comply with the provisions in the following table:
project
Class a class B
Summer winter all year round
Temperature (℃) 23 ± 2 20 ± 2 18-28
Relative humidity (%) 45-65 40-70
Temperature change rate (℃ / h) < 5 < 10
During shutdown, the temperature and humidity in the machine room shall comply with the provisions in the following table:
project
Class a class B
Temperature (℃) 5-35
Relative humidity (%) 40-70 20-80
Temperature change rate (℃ / h) < 5 < 10
When starting up, the temperature and humidity in the main engine room shall be class A, the basic workshop can be class A and B according to the equipment requirements, and other auxiliary rooms shall be determined according to the process requirements;
The dust concentration in the air in the main engine room shall be tested under static conditions, and the dust concentration in each liter of air shall be ≥ 0.5 μ The number of dust particles per m shall be less than 18000.
2) Noise, electromagnetic interference, vibration and static electricity
When the computer system is shut down, the noise in the main engine room shall be less than 68dB (a) measured at the operator's position;
Radio wave interference affects the working stability of many electronic equipment. Computer work belongs to weak and small signals and is very sensitive to interference. Therefore, necessary anti-interference processing - grounding or shielding should be done to make the radio wave interference field strength of the working environment lower than 126dB when the frequency is 0.15-1000mhz;
The working environment shall be protected from permanent magnetic field or electromagnetic field interference, and its value shall not be less than 800A / m. Therefore, the distance between the placement position of computer and other equipment and high-pressure equipment such as substation shall be kept more than 5m;
The electrostatic leakage resistance of the ground and worktable of the main engine room shall comply with the provisions of the national standard technical conditions for raised floor for computer room; The electrostatic potential of the insulator in the main engine room shall not be greater than 1KV.
3) Grounding of machine room
According to the national standard 2887-89 technical requirements for computer station grounding, the computer room shall adopt the following four grounding modes:
For AC working grounding, the grounding resistance shall not be greater than 4 Ω;
For safety protection grounding, the grounding resistance shall not be greater than 4 Ω;
DC working grounding can be divided into DC grounding suspension and DC grounding direct grounding. From the perspective of safety, DC grounding should be directly grounded;
For lightning protection and grounding, the grounding resistance shall not be greater than 10 Ω.
In the central machine room, AC working grounding, safety protection grounding, DC working grounding and lightning protection grounding share a group of grounding devices, and the grounding resistance is less than 1 Ω.
4) Fire alarm and extinguishing system of machine room
The computer room is equipped with automatic fire alarm system;
Automatic fire detectors are set on the ceiling of the machine room, which are uniformly distributed, and the protection area of each detector is 10-15 square meters;
Automatic fire detector adopts smoke detector;
According to the situation of the computer center, the fire extinguishing system in the machine room is equipped with carbon dioxide or halogenated alkane fixed fire extinguishing system.
5) Ventilation requirements
In order to ensure that the fresh air in the central machine room is continuously supplemented and the old air is continuously discharged outdoors, it is necessary to set a ventilator in the central machine room.
6) Consideration of maintenance power supply
According to relevant requirements, AC 220V maintenance power sockets shall be installed in each room of the central machine room and each building wiring room. The installation height of the power socket is 300mm from the movable anti-static floor.
10. System shielding and grounding
1) Shielding effect
When there is electromagnetic interference in the surrounding environment of generic cabling system, shielding measures shall be taken to suppress electromagnetic interference. Cable is not only the main generator of cable trunk, but also the main receiver. As a generator, it radiates electromagnetic noise field to space; Sensitive TV sets, computers, communication systems and data systems receive this electromagnetic noise through their antennas, interconnects and power lines.
The most basic of using shielding system is to ensure the transmission performance of wiring system in interference environment. The interference here includes two parts: reducing electromagnetic radiation, that is, reducing the outward radiation energy of the wiring system itself. And improve the ability to resist external electromagnetic interference. The cable shielded separately by wire pairs also has the ability to reduce crosstalk between wire pairs.
In order to eliminate interference, in addition to the discontinuity point of the shielding layer, it is also required that the shielding system must achieve complete continuous 360 degree complete shielding. A complete shielding system requires shielding everywhere. First, the shielding at any point can not meet the requirements, which will inevitably affect the overall transmission performance of the system. This requirement is difficult to achieve for the connection between ground wire and a point-to-point connection. Because of the information socket, jumper, etc. It is difficult to shield, so shielding can not completely eliminate electromagnetic interference. In addition, the voltage difference between the grounding points of the shielding layer will lead to grounding noise, such as excessive grounding resistance, unbalanced grounding potential, etc. In this way, there will be a potential difference between some two points of the transmission system, which will produce the current on the metal shielding layer. At this time, the shielding layer itself has become the largest interference source, resulting in its performance is far inferior to the unshielded twisted pair.
For the shielding system, it is not enough to have only a metal shielding layer. More importantly, there should be a correct and good grounding system to effectively introduce interference into the earth, so as to ensure the safe and reliable transmission of signals in the shielding system.
2) Type of grounding
The grounding of generic cabling system shall be considered together with the active equipment grounding system placed in the equipment room and wiring room. The grounding system meeting the requirements of active equipment must also meet the grounding requirements of generic cabling system.
Grounding is divided into DC working grounding, AC working grounding, safety protection grounding, lightning protection grounding, anti-static grounding and shielding grounding.
In the grounding system, the grounding resistance is used to represent the index of good or bad combination with the earth. The grounding resistance value is specified in the technical requirements for calculating station grounding as follows:
The DC working grounding resistance shall not be greater than 4 Ω;
The AC working grounding resistance shall not be greater than 4 Ω;
The safety protection grounding resistance shall not be greater than 4 Ω;
The grounding resistance of lightning protection shall not be greater than 10 Ω.
The grounding resistance of integrated grounding shall not be greater than 1 Ω.
3) Grounding requirements of distribution cabinet
The shielding layer of all shielding wires shall be well grounded. The shielding layer shall first be connected to the grounding terminal of the floor distribution cabinet, and the grounding terminal of each floor distribution frame shall be connected to the grounding device in the distribution room.
The DC resistance of the grounding conductor from the building distribution frame to the grounding device shall not exceed 1 Ω and shall be permanently connected.
4) Grounding conductor requirements
Within 30m from the grounding body (from the appropriate grounding point), the grounding conductor shall be multi strand copper core wire with 4mm Diameter wrapped with insulating sleeve.
If the distance from the grounding body is more than 30m, the diameter of the grounding wire is shown in the table below:
Distance (m) conductor diameter (mm)
≤ 30 4.0
30-48 4.5
48-76 5.6
76-106 6.2
106-122 6.7
122-150 8.0
151-300 9.8
Each distribution frame in the distribution room shall be reliably grounded to the grounding bar of the distribution frame (cabinet), and its grounding conductor shall not be less than 2.5 mm2, and the grounding resistance shall be less than 1 Ω.
11. System test
1) Copper cable test
Perform basic link test for each cat 5 information port, and the test items include:
Information port and connector in work area
Horizontal line from work area to telecommunication room
Distribution frame interface in telecommunication room
During the test, all the following parameters must meet the standards set by EIA / TIA 568a TSB 67:
The wiring diagram (wiremap) is correct
Length of horizontal twisted pair < 90m
Line attenuation < 23.2db
Near end cross talk / next > 24dB
2) Optical cable test
Test standard: the test of optical cable transmission performance can refer to GB / T 8401.
(1) Light attenuation
Whether it is the horizontal wiring subsystem, the building backbone wiring subsystem or the building cluster backbone wiring subsystem, the optical attenuation of each core optical fiber in the optical cable shall not exceed the specified values in the table below.
Optical attenuation of each subsystem of optical cable wiring:
Type single mode optical attenuation (DB) 1310nm single mode optical attenuation (DB) (1550nm) multimode optical attenuation (DB) (850nm) multimode optical attenuation (DB) 1300nm
Flat line (100m) 2.2 2.2 2.5 2.2
Building wiring (500m) 2.7 2.7 3.9 2.6
Building group wiring (1500m) 3.6 3.6 7.4 3.6
(2) Full range light attenuation
For the optical cable wiring link composed of several subsystems, at the working wavelength point, the whole process optical attenuation of each core optical fiber shall not exceed 11db. In terms of the above tests, all twisted pair cables connected from the distribution frame to the data network equipment shall be performed. During the test, if any information port fails to pass the test, it shall be inspected, repaired or replaced until it passes the test. When the whole wiring project is completed, all the test reports will be submitted to the user together with other documents for record.