Electrical protection of the hottest generic cabli

2022-08-17
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Electrical protection of generic cabling system

generic cabling system is a part of intelligent building. Compared with traditional cabling, its main characteristics are compatibility, openness, flexibility, reliability, progressiveness and economy. It can not only connect voice, data, image equipment and switching equipment with other information management systems, but also connect these equipment with external communication networks. It can be said that generic cabling system is like a highway of intelligent buildings. With this information highway, it becomes very simple to use any application system. The purpose of electrical protection of generic cabling is to reduce the damage of electrical faults to the cables and related connecting hardware of generic cabling, avoid the damage of terminal equipment or devices, and ensure the normal operation of the system

I. electrical protection

when the outdoor cable enters the building, it usually enters the room through a transfer at the entrance. Electrical protection equipment should be installed at the transfer place, so as to avoid the damage to the user's equipment caused by the induced potential of the cable caused by lightning strike or contact with the power line

electrical protection is mainly divided into overvoltage protection and overcurrent protection. These protection devices are usually installed in the special room or wall at the entrance of the building

the overvoltage protection of generic cabling can choose gas discharge tube protector or solid-state protector. The gas discharge tube protector uses disconnection or discharge gap to limit the voltage between conductor and ground. The discharge gap is formed by two metal electric poles sealed in the ceramic shell and filled with inert gas. When the potential difference between the two electrodes exceeds 250V AC or the lightning surge voltage exceeds 700V, the gas discharge tube will produce an arc, providing a conductive path between the conductor and the ground electrode

solid state protector is suitable for low breakdown voltage (60 ~ 90V), and there should be no ringing voltage in its circuit. It uses electronic circuits to discharge excessive harmful voltage to the ground without affecting the transmission quality of the cable. Solid state protector is an electronic switch, which can conduct stable voltage clamping before reaching the breakdown voltage. Once the breakdown voltage is exceeded, it will introduce the overvoltage to the ground. Solid state protector provides the best protection for generic cabling

in addition to overvoltage protection, the generic cabling system also adopts overcurrent protection. In the series circuit of overcurrent protector, when the line has overcurrent, it will cut off the line. For the convenience of maintenance, overcurrent protection generally adopts protectors with automatic recovery function

II. Shielding effect

electromagnetic interference and radiation are the problems of the whole application system. The interference caused by generic cabling cable is only a part of it, and the radiation energy is related to the voltage and frequency of the transmitted signal. Shielding is used to ensure the transmission performance of generic cabling channels in an interfering environment. It includes two parts: reducing the energy radiated by the cable itself and improving the ability of the cable to resist external electromagnetic interference

the plastic in the cavity cannot be supplemented in time after shrinkage. The overall performance of generic cabling depends on the performance of the weakest cable and related connecting hardware in the application system and the connection process when any load is applied. In generic cabling, the weakest link is the contact between distribution frame and cable connecting parts, as well as information socket and plug. When the shield of shielded cable cracks in the installation process according to the use of the machine and the service life of the oil, it also constitutes a weak link in the shielding channel. In order to eliminate electromagnetic interference, in addition to requiring that there is no discontinuity in the shielding layer, it is also required that the overall transmission channel must achieve 360 ° full shielding. This requirement is difficult to achieve for a point-to-point connection channel, because the addition of jiayirong tmemi ⑵ 00 to the information in it can effectively improve the material plasticization, sockets, jumpers, etc., which are difficult to achieve full shielding. In addition, factors such as the corrosion of the shielding layer, oxidation damage, etc., therefore, No channel can be completely shielded. At the same time, the shielding layer of the shielded cable has poor shielding effect on the low-frequency magnetic field, and cannot resist the low-frequency interference generated by equipment such as motors. Therefore, the use of shielded cables can not completely eliminate electromagnetic interference

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