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This article will explain in detail how to install the shielded cabling system in the server. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

The way of shielded wiring originated in Europe, which mainly adds a metal shielding layer to the outside of the ordinary unshielded wiring system, and the principle is to make use of the emission, absorption and skin effect of the metal shielding layer. it is mainly reflected in that it has a strong ability to resist external electromagnetic interference and radio frequency interference, but also can prevent internal transmission signals from radiating energy to the outside world, and has good system security. The shielding system makes comprehensive use of the principle of twisted pair balance and the shielding effect of the shielding layer, so it has very good electromagnetic compatibility (EMC) characteristics. In addition, shielded cabling has gradually shown its advantages in electromagnetic compatibility, which has been used in Europe, the United States, North America and many other countries.

At present, there is an objective debate about "shielding and non-shielding" in the industry, but we think that as each kind of wiring solution, there is a basis for its existence, or it has its own advantages and disadvantages. It is one-sided and irresponsible to comprehensively negate a certain type of cabling scheme. Both shielded cabling system and unshielded cabling system are widely used, based on the advantages of shielded cabling can help the rapid development of the Internet, many large data centers use shielded cabling system, so the use of shielded cabling system is one of the main trends of network wiring in the future.

According to the statistical data, 42.2% of the respondents think that shielded cabling construction is difficult, and 21.2% of the interviewees think that it is difficult to maintain the shielded cabling system. however, only 20.6% of the respondents considered it difficult to plan and design the shielding cabling system. it seems that the worry about the shielded cabling system has shifted from the field of planning and design to the construction of shielding cabling. And maintenance has also begun to be valued by people. For a shielded wiring system, to reflect its characteristics, in the design and construction, we need to pay attention to the following two points:

The function of the shielded wiring system requires that all connection hardware use shielded products, including transmission cables, distribution frames, modules and jumpers.

The installation of the shielded wiring system must be correct and well grounded, and if the shielding layer of the connected components of the transmission channel is discontinuous or poorly grounded, the transmission performance may be worse than that provided by the unshielded system.

Installation of shielded wiring system

The installation of shielded wiring system mainly involves two aspects: the terminal connection of shielded cable in floor wiring closet and work area and system grounding.

In view of the particularity of the shielding system, it is necessary to ensure that the shielding layer of the cable has good contact with the shielding layer of the module and distribution frame in the range of 360 degrees, rather than connecting at some points, and the shielding layer can not be broken in the middle of the same link.

Step 1: use a special termination tool to remove the sheath of the shielded cable

Step 2: separate the 4 pairs of twisted-pair core wires, do not disassemble each pair of core wires, according to the color sequence of core wires indicated on the information module, pull a small section of corresponding core wires horizontally with both hands, and place the wires into the corresponding slots one by one with a little effort.

Step 3: after all the core wires are embedded, you can press the core wires into the wire slot one by one with wire pliers. Aim the knife edge of the marking tool at the wire slot and wire on the information module, and the excess wire outside the module is cut. Repeat this while connecting the drain line in the cable to the metal sheet at the back of the module.

Step 4: the plastic dustproof sheet of the information module is pierced into the twisted pair along the gap and fixed on the information module, then the iron cover of the module is covered, and the whole process of making the module can be completed after pressing. Then put the finished information module into the information socket.

Step 5, after the information module is made, you can also test whether the connection is good or not. At this time, you can use a multimeter to measure. Hit the gear of the multimeter in the resistance file of x10, contact one of the watch needle of the universal bead with the corresponding core wire at the other end of the wire, and the other universal watch pen contacts the edge of the card slot of the corresponding color core wire on the contact information module (note that it is not touching the core wire). If the resistance value is very small, it proves that the information module is connected well, otherwise press the corresponding core wire with wire clamp until it is smooth. You can also use a professional tester, such as FLUKE, to choose different shielding testing standards according to different objects.

A complete shielding and wiring system installation requires shielding everywhere, a continuous and complete shielding path, in order to achieve the desired results of users. If you choose to use shielding system, in addition to cables, modules, distribution frames and other connectors need to use shielding, supplemented by metal bridges and pipes. The principle of electrostatic shielding is to make the interference current flow into the earth through the outer layer of the shield, so the proper grounding of the shield is very important.

Earthing

The proper grounding of the shield is very important, otherwise the interference will not be reduced, but will increase. Because when the grounding location is arranged incorrectly, the grounding resistance is too large, and the grounding potential is not balanced, it will cause grounding noise, that is, the potential difference between two points of the transmission channel will occur, resulting in interference current on the metal shielding layer. At this time, the shielding layer itself forms an interference source, resulting in its performance far inferior to that of the unshielded transmission channel. Therefore, in order to ensure the effect of the screen, the shield must be grounded correctly and reliably.

The grounding accessory in the shielded distribution frame is the bus for grounding, through which all the shielding modules can be connected to the unified grounding body to form the grounding channel in the distribution frame.

There are two main types of grounding accessories for shielded distribution frames.

1. Grounding fittings installed in the distribution frame

The grounding fittings installed in the distribution frame are flexible. When the installation module of the shielded wiring system is inserted into the distribution frame, the metal shell automatically forms a good connection with the grounding accessories, and the grounding work of the shielding module is completed.

two。 Independent grounding fittings

Independent grounding accessories can be transformed from a special unshielded distribution frame to a shielded distribution frame, and this kind of shielding module generally contains a grounding interface for pluggable lap wiring. When the shielding module is inserted into the distribution frame, the lap wire in the grounding accessories is inserted on the grounding interface of the shielding module to form the grounding connection of the shielding module.

Grounding piles should be installed on the distribution frame so that the grounding wires from the cabinet can be overlapped with them. The traditional shielded distribution frame is grounded by metal posts in the cabinet, which is no longer used.

The shielded grounding of the distribution frame can be done in the following ways:

Each shielded distribution frame is connected to the bus copper bar of the cabinet through its own grounding wire to form a star grounding structure.

A grounding copper bar is installed at the bottom of the cabinet, and an independent grounding wire is used to connect the grounding copper bar to the grounding pile (grounding copper bar) in the distribution room (telecommunication room), so that the grounding between the cabinets forms a star grounding structure.

The cross-sectional area of grounding wire should be larger than 6mm2.

The cold-rolled welding pads commonly used by electricians should be used at both ends of the grounding wire to prevent the wire ends from spreading to form a short circuit.

In order to improve the release capacity of high frequency interference signal, it is suggested that the grounding wire should be woven to meet the skin effect of high frequency current with larger surface area.

Let's look at the problems related to shielded cabling in the process of network cabling:

1. What are EMC features?

EMC is electromagnetic compatibility, which means that electronic equipment or network system has a certain ability to resist electromagnetic interference, at the same time can not produce excessive electromagnetic radiation. In other words, the equipment or network system is required to work normally in a relatively harsh electromagnetic environment, at the same time, excessive electromagnetic waves can not interfere with the normal work of other equipment and networks around.

two。 How to measure the performance difference between shielded and unshielded systems?

The advantage of FTP cable shielding system is that it provides better EMC performance than UTP cable, which is based on isolating the system from the external electromagnetic environment. Because the external electromagnetic environment will affect the data transmission of the whole wiring system. So far, there are no performance metrics or test methods to express or compare EMC performance.

3. UTP cable is an ideal balanced transmission system, why use FTP cable?

The UTP cable achieves EMC performance through the twisted pair of the core, which means that the EMI is first received by the UTP cable and then offset. However, with the increase of frequency, the EMC performance of UTP will decline. After measurement, it is found that the twisted pair of cable can only meet the EMC performance of 30MHz, and will be used as force for higher EMI twisted pair. So far, most practical network applications work at a lower frequency than 30MHz.

Moreover, the ideal balanced transmission system does not exist. The balance characteristics of UTP cables depend not only on the quality of the components themselves (such as twisted pairs), but also on the surrounding environment. Because the metal around UTP, concealed "ground", traction during construction, bending and so on, will destroy its balance characteristics, thus reducing the performance of EMC.

In fact, when we install a cable, we usually insert it into a metal conduit, plastic conduit, or other protection with different grounding impedance. Therefore, in order to achieve lasting ground performance, there is only one solution: an extra layer of aluminum foil is added to all the core wires for grounding. Aluminum foil adds protection to the fragile twisted pair and creates an artificial balance environment for UTP cables. This means that shielding solutions based on FTP cables are environment-specific, that is, environment-independent. FTP combines the balance characteristics and construction flexibility of UTP with the shielding effect of STP, that is, the combination of balance and shielding principle.

4. What is the shielding principle of FTP cable?

Different from the balance cancellation principle of twisted pair, FTP cable adds one or two more layers of aluminum foil to the outside of four pairs of twisted pair, using the principle of reflection, absorption and skin effect of metal to electromagnetic wave (the so-called skin effect means that the distribution of electric current in the cross section of conductor tends to the distribution of conductor surface with the increase of frequency, and the higher the frequency is, the smaller the skin depth is, that is, the higher the frequency is, the weaker the penetration ability of electromagnetic wave is.) It can effectively prevent external electromagnetic interference from entering the cable, and at the same time prevent internal signals from radiating out and interfere with the work of other equipment.

The experimental results show that the electromagnetic wave whose frequency exceeds 5MHz can only pass through 38 μ m thick aluminum foil. If the thickness of the shield is more than 38 μ m, for example, Nixon's FTP cable is shielded by two layers of 25 μ m thick aluminum foil, the frequency of electromagnetic interference that can enter the cable through the shield is mainly below 5MHz. The twisted pair principle can be used to effectively cancel the low frequency interference below 5MHz.

In the installation project of shielded wiring system, in addition to the need for high-quality wires and connectors, good construction skills and meticulous working attitude are essential. Pay attention to the details of the construction process, do a good job of each grounding link in the shielding system, I believe that we can make a high-quality shielding project.

This is the end of the article on "how to install the shielded cabling system in the server". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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