Comprehensive wiring system shielding technology detailed

Integrated wiring system with cutting-edge technology and intelligent design, with unparalleled superiority. The integrated cabling solution delivers a complete end-to-end solution that includes copper and fiber based solutions, high performance components in the design to achieve the most perfect match, and the choice of UTP, FTP, or STP cables to meet current and future requirements over five categories, Six or future seven types of copper technology and innovative optical fiber solutions form a fiber to the desktop of the Information network. The innovation of the Integrated Cabling solution provides the network with sufficient reliability and bandwidth, so that we are always at the forefront of the wiring technology.

Integrated wiring products, whether the shield system or shielding system has a wide range of use and can be tailored to different user needs (the network's operating frequency and the surrounding electromagnetic environment is different) to provide a variety of end-to-end solutions, including shielding, unshielded and fiber cabling solutions. However, the shielding system will be very suitable for interference and confidentiality requirements (such as government agencies, military installations) or the following electromagnetic environment.

Integrated wiring network in the building inside the distribution box and distribution network generated high-frequency interference, the harmonic interference caused by electric spark of high power motor, the ringing current of fluorescent lamp, electronic starter, power switch, telephone network, the periodical pulse caused by information processing equipment and so on, should adopt shielding system when unable to maintain safe interval.

Integrated wiring network in the building outside the existence of radar, radio transmission equipment, mobile phone base station, High-voltage wire, electrified railway, lightning zone and other sources of interference, if in high electromagnetic field intensity of the environment should be used shielding system. ---http://bianceng.cn (computer science)

The interference signal field strength of the surroundings or the noise level of the integrated wiring system should adopt the shielding system when exceeding the following regulations:

(1) The field strength of the 10khz~600mhz jamming signal is 1v/m by the computer LAN, and the 600~80mhz interference signal is 5v/m.

(2) The telecommunication Terminal equipment is introduced into RFO through the introduction line of signal, DC or AC. The field intensity of 15~80mhz jamming signal is 3V amplitude modulation 80% 1kHz;

(3) The total bandwidth of the noise level exceeding -40dbm is less than 200MHz when the terminal equipment with analog/digital Terminal interface provides telephone service;

(4) When the terminal equipment provides the acoustic interface service, the total bandwidth of the noise level exceeding the reference level is less than 200MHz.

1. Shielding Technology

Shielding wiring system from Europe, it is in the ordinary unshielded wiring system outside the metal shielding layer with the metal shielding layer of reflection, Absorption and skin effect to prevent electromagnetic interference and electromagnetic radiation function shielding system comprehensive utilization of the balance principle of twisted pair and shielding effect of shielding layer has very good electromagnetic compatibility (EMC) characteristics. Most end users in Europe will opt for a shielded wiring system, especially in Germany, where about 95% of the users are installed as shielding systems while the other 5% are installed as optical fibres.

At present, the shielding cabling system has been recognized by more and more users for its good performance in electromagnetic compatibility. Shielding wiring products in the market, in addition to imports in Europe, more and more manufacturers also provide shielding wiring products. In the latest North American cabling Tia/eia-568-b Standard, shielded and unshielded cables are also used as a recommended medium for horizontal wiring, thus ending the history of no shielding systems in North America. In China, more and more users, especially those involving the secrecy and radiation intensity of the project, began to pay attention to and use of shielding systems, even six types of shielding systems.

Shielded wiring system has a complete set of shielding, grounding theory and product line, to provide the most complete, most comprehensive cable, components and end-to-end total shielding solutions to meet the growing needs of today's network. Of course, the current industry on the shielding wiring system, some of the controversy may also make the user is not very understanding of shielding system.

The shielding principle of the FTP cable is different from the balance cancellation principle of the twisted pair. The FTP cable is four pairs of twisted-pair outside the outer layer or two layer of aluminum foil, the use of metal to the electromagnetic wave reflection, absorption and skin effect principle (the so-called skin effect is the current in the conductor section of the distribution with the frequency of increase and tend to the conductor surface distribution.) The higher the frequency, the smaller the skin depth, that is, the weaker the penetration of electromagnetic waves, effectively prevent external electromagnetic interference into the cable, but also prevent the internal signal radiation to interfere with other equipment work.

Experiments show that the frequency of more than 5MHz of electromagnetic waves only through 38μm thick aluminum foil. If the thickness of the shielding layer exceeds 38μm, such as Nike Sen's FTP cable for the two-layer 25μm thick aluminum foil shielding, so that through the shielding layer into the cable inside the frequency of electromagnetic interference is mainly below 5MHz, and for 5MHz below the low-frequency interference can be effectively offset the principle of twisted pair.

2. Transmission Media

The transmission medium used in wiring system mainly has twisted pair and optical cable. The twisted pair is composed of two insulated copper conductors, which are divided into unshielded twisted pair (UTP) and shielded twisted-pair STP, while the shielded twisted pair is divided into aluminum foil shielded twisted pair ftp, independent shielded twisted pair (STP). How to select the system transmission medium is an important content in the construction, the technical performance comparison of UTP, FTP, STP cable please refer to table 1, 2 (ignore, see this issue of magazine).

In the system wiring, the use of shielded twisted pair or the use of unshielded twisted pair, in the industry is still in dispute. People who stick to the idea of non-shielding think: shielding system is the whole process of shielding the entire system, which itself is a good idea, can improve the speed of signal transmission, but the installation standards are high, investment, although the shielding can resist noise interference, improve transmission rate, but if the wiring process in the slightest careless, Will affect the entire system shielding effect, but will reduce the performance of the system, the full shield wiring transmission bandwidth, lower than the same cost of the multi-edge fiber; From the performance-price ratio, the horizontal wiring subsystem will still be unshielded twisted-pair and fiber-optic world. The person who holds the view of shielding thinks: the shielding system can improve the stable performance and high quality transmission signal, can provide high transmission bandwidth, can support the future high-speed network system, and improve the farther transmission distance. High construction requirements are professional installation of the company, as long as strictly in accordance with the specifications of the wiring requirements operation, will provide users with shielding wiring system.

Wiring system using unshielded twisted-pair or shielded twisted-pair line, from the construction quality, duration and investment to see there are obvious differences. Non-shielded twisted-pair cable is adopted in unshielded system, the construction is simpler, the quality standard is low, the construction period is short, and the investment is low. and shielding system using shielded twisted-pair, the shielding layer processing requirements are very high, in addition to the need to link the shielding layer can not have breakpoints, but also requires the shielding path must be complete the entire process of shielding. From the current construction conditions, it is difficult to achieve the entire system of the whole process of shielding. Therefore, it is necessary for designers to understand the technical indexes of unshielded twisted pair, shielded twisted pair and optical fiber in the choice of voice communication, data communication and transmission medium of image communication. Voice communication: 3 or higher 100ω unshielded twisted pair; general Data communication: 5 class 100ω unshielded twisted pair, 150ω shielded twisted pair; high-speed data communication: 2-Core 62. 5/125μm optical fiber; visual communication: Class 5 100ω unshielded twisted pair, 2-core 62. 5/125μm optical fiber and so on.

3. Balanced transmission

UTP Cables achieve EMC performance through the twisted pair of core wires. This means EMI is first received by UTP Cable and then offset. However, as the frequency increases, the EMC performance of UTP will decrease. The measurement found that the cable pair can only meet the 30MHz of EMC performance, for higher electromagnetic interference will be powerless. At present, most of the actual network applications operating frequency is lower than 30MHz, and the ideal balance transmission system does not exist. The balance characteristics of UTP cables are not only determined by the quality of the parts themselves (such as twisted pair), but are affected by the surrounding environment. Because of the metal around UTP, hidden "ground", the construction of the pull, bending and so on will damage its balance characteristics, thereby reducing EMC performance. In fact, the cable that we install usually wears it into a metal conduit, a plastic conduit, or other protection with a different grounding impedance. So there is only one solution to achieve a durable, unchanging performance: the grounding of a layer of aluminum foil on all core wires. Aluminum foil provides protection for fragile twisted-pair cores while creating a balanced environment for UTP cables. This means that the shielding solution based on the FTP cable is independent of the environment, which is not related to the environment. FTP is the integration of UTP balance characteristics and construction flexibility and STP shielding effect, that is, balance and shielding principle of the perfect combination.

3. 1 FTP, UTP attenuation

The attenuation index of FTP cable is in full compliance with iso/iec11801 and eia/tia568b and other related standards. If the UTP cable is pierced into the metal conduit, its impedance characteristic will decrease and cause the attenuation to increase. The FTP cable has been compensated for in the manufacturing process, taking into account the effects of the surrounding aluminum foil.

3. 2 FTP, UTP transmission distance

The transmission distance of the cable is determined by the attenuation of the cable and the propagation delay, which is not related to the shielding. The most critical factor affecting transmission distance is the propagation delay, which is determined by the NVP value of the cable: the NVP of the ordinary UTP cable is about 0. 66 Nike Sen's UTP, FTP, STP cable NVP at 0. 68 or so.

3. 3 Radiation and grounding

The shielding performance of the system is determined by the performance of the worst part, the weakest part of the shielding system is the information socket and the modular jumper disk in the cabinet can improve its EMC performance by moving away from interference sources, such as elevators, air-conditioning, power equipment, fluorescent lamps, mobile communication base stations, etc. And the use of an information socket with an EMC shield and jumper disk, cable parts and information outlets and jumper disk, the cable is widely distributed throughout the building, the surrounding electromagnetic environment more complex, unpredictable and control, so the cable is part of the entire wiring system need to be the most electromagnetic protection part.

The shielding principle of the FTP cable can be understood that the shielding layer is not grounded also has shielding effect, the shielding effect of aluminum foil shielding and grounding has nothing to do. But if the grounding is not good the FTP shielding layer will become the interference source. Integrated wiring system as a passive product, itself will not produce electromagnetic radiation, but if the grounding of the defective cable shielding layer will absorb external electromagnetic interference, conduction and outward radiation. Of course, outward radiation also requires a certain condition, that is, the energy required for radiation and its antenna size and wave wavelength in the same order of magnitude. Only the shielding layer that satisfies the above condition cable can become "potential antenna". In the development and development of the whole system, the problem of high frequency grounding has been fully taken into account, and the large area surround grounding of the cable shielding layer has been realized to avoid the so-called "antenna effect".

3. 4 Measurement Shielding

The advantage of the FTP cable shielding system is to provide better EMC performance than UTP cabling, which is based on isolating the system from the external electromagnetic environment, because the external electromagnetic environment affects the transmission of the entire cabling system. So far, there are no performance metrics or test methods to express or compare EMC performance. However, the European Committee for Standardization (CENELEC) has started this work, coupled attenuation coupling attenuation is defined as the metric for measuring EMC performance, which is also written in the second version of the international wiring standard iso/iec11801.

4 Shielding Wiring System

Nike's shielding cabling system consists of F2TP/STP shielded cables and corresponding shielded connectors, jumpers and other components of the product line covers the Super Five class (class D99), six Class E and seven class (Class F). Its cable comprehensive use of balance and shielding technology, greatly improve the system's resistance to electromagnetic interference EMI and electromagnetic radiation to prevent EMR's ability, that is, the system has a very high EMC performance electromagnetic compatibility. The shielding products are obtained by the Danish Independent Electronics Laboratory Delta, the United States Insurance Laboratory UL and the United States ETL testing and certification agencies. At the same time, its series of wiring products indicators far higher than the iso/iec11801, eia/tia568a and EN50173 standards.

4. Characteristics and advantages of 1 shielding system

The shielding layer of shielded cable consists of two layers of aluminum foil, which not only greatly improves the shielding performance of the cable, but also facilitates the installation. F2TP Cable uses the world's unique Double-layer longitudinal package aluminum foil shielding structure, that is, the outside of the UTP cable longitudinal two layers of 25μm thick aluminum foil, so as to avoid the cable bending or heating when the shielding layer appeared small gap, and reduced the transfer impedance, improve the shielding effect, At the same time make grounding (including shielding grounding and protection grounding) more convenient and reliable. Because the Double-layer aluminum foil structure greatly simplifies the connection of shielded cable, save the installation time, so that the installation of Double-layer aluminum foil FTP cable is as simple as the installation of UTP cable. The Double-layer aluminum foil consists of two layers of aluminum foil (conductor layer) and plastic film (insulating layer) deposited on its surface, which is relative to the conductor layer. When the cable ends, it is very easy to remove the outer sheath of the cable and the shielding layer outside, exposing a layer of shielding layer, the conductor layer outward. From the aspect of EMC, the shielding layer of the cable must be in contact with a large area of metal surface, that is, the so-called 360 ℃ grounding grounding. In the double layer aluminum foil shielding system, just inside a layer of shielding card (Nike Sen patented products Clip-ontm) card on the cable rack, to ensure that the shielding cable in the wiring racks and information sockets to achieve 360 ℃ surround grounding (grounding), will never produce the so-called "antenna effect." The CLIP-ONTM cable frame is integrated with the modular wiring tray to achieve continuous shielding within the entire link, with an EMC enclosure and a dedicated cable conductor frame.

For more than 10MHz of electromagnetic waves, using the shielding layer of reflection, absorption and skin effect mechanism to offset electromagnetic interference and electromagnetic radiation. The higher the frequency, the more obvious the effect of shielding layer. For low-frequency, less than 5MHz electromagnetic wave, the balance of twisted pair is used to cancel. This double-layer aluminum foil shielded cable has the greatest characteristics of two aspects: excellent shielding performance, maximum convenience for users to install.

4. 2 Grounding System

When the integrated wiring system adopts shielding measures, it must have a good grounding system. and shall comply with the following provisions:

(1) The grounding resistance value of the protective ground wire shall not be greater than 4 Ω when the grounding body is individually set, and shall not be greater than 1 ω when the joint grounding body is used;

(2) When the shielding wiring system is used, all shielding layers should be kept continuous;

(3) The use of shielding integrated wiring system, the shielding layer of the wiring equipment FD or BD End must be good grounding, the client, terminal equipment, depending on the circumstances of the ground. The grounding of both ends shall be connected to the same grounding body. If there are two different grounding systems in the grounding system, their grounding potential difference should not be greater than 1VR. M s valid value;

(4) The use of shielding wiring system, each floor of the wiring cabinets should be the appropriate cross-section of copper wire to the grounding of the individual wiring, can also be used in the shaft centralized copper or coarse copper wire to the grounding, wire or copper conductor cross-section should conform to the standard. The grounding conductor bell into a tree-like grounding net to avoid forming a DC loop;

(5) Integrated wiring of the cable using metal channels or steel pipe laying, channel or steel pipe should maintain continuous electrical connection, both ends should be good grounding.