Summary of precautions for cabling system application

Key Points of Grounding Design for cabling systems

For the majority of engineering and technical personnel, improving the stability and reliability of the Integrated Wiring and grounding system will be a long-term and arduous task, so we should understand the issues that should be paid attention to when designing the grounding of the Integrated Wiring System.

1. When the Integrated Wiring System adopts shielding measures, the continuity of all shielding layers should be maintained and the relative positions between wires should be kept unchanged. The FD or BD end of the shield layer shall be grounded, and the user terminal equipment shall be directly grounded according to the specific situation. The grounding at both ends shall be connected to the same grounding body as far as possible. When there are two grounding bodies in the grounding system, the Grounding Potential Difference should not be greater than 1Vr. m. S valid value ).

2. When a cable enters the building from the outside, it is easily affected by lightning strikes, power touch, power induction potential, ground potential floating, and other external factors, a protective device must be used.

3. When the line is in any of the following dangerous environments, it should be protected against overvoltage and overcurrent:

1) dangerous effects caused by lightning strikes.

2) power supply lines whose operating voltage exceeds v touch the ground;

3) power failure caused by the increase of ground potential to over V;

4) The AC 50Hz induction voltage exceeds 250 V.

4. For the overvoltage protection of the Integrated Wiring System, the gas discharge tube protector should be used. Because the Ceramic Housing of the gas discharge tube protector is sealed with two electrodes, there is a discharge gap between them, and there is a inert gas. When the potential difference between two electrodes exceeds v ac voltage or V lightning surge voltage, the gas discharge tube begins to have an arc, providing a conductive path between the conductor and the ground electrode.

5. The overcurrent protection of the Integrated Wiring System should be self-healing. Due to the possibility of one voltage or another on the cable, if the connection device provides a low-resistance path to the ground, it is not enough to enable the overvoltage protector to operate, the current may damage the device or cause fire. For example, the 20 V power line may be insufficient to discharge the overvoltage protector, but may generate a large current into the device, causing damage. Therefore, the over-voltage protection must be used at the same time. The self-recovery overcurrent protector is required to facilitate maintenance.

The cabling system should be protected against moisture

The incoming traffic of the data cabling system has a significant impact on the cable's ability to support high-speed data applications. In some cases, a cable that is close to the maximum link length specified by the standard may become invalid in case of water inflow. This is because when the cable gets wet, its insulation performance changes and may affect the impedance, attenuation, ripple loss, and other related parameters.

It is generally believed that the PVC material that covers the outside of the standard data cable is waterproof. In fact, the PVC material is moisture-absorbing. Both the standard cat5e and cat6 cables use PVC jackets for indoor design and are not suitable for wet environments.

For outdoor environments with different levels of fog or water, the cables are designed to take waterproof measures, such as blocking tape and gel filling, which are costly and sometimes reduces electrical performance. Moreover, these waterproof gel is based on petroleum and has fire hazards, except for links unsuitable for indoor use ).

The impact of water inflow also depends on the source of water and the time of water inflow. The PVC cable is exposed to a small amount of clean water in a short period of time, without any long-term adverse effects. The low smoke and Zero Halogen cable directly laid on the concrete floor, if no pipelines or protective measures are used, the loss risk will be much greater as long as the water is flooded for a week; water from dusty cement floors, containing dissolved pollutants, will pose a greater risk.

Changing damp cabling systems is time-consuming, costly, and destructive. Obviously, the best way is to prevent cable moisture. Enterprises located in highly dangerous areas should consider the risks of moisture in the network design phase. Measures should also be taken for existing cabling networks.

If possible, the cables should be suspended in the pipe in the ceiling space, which is more dangerous than under-floor wiring. By using pipelines, such as cable racks, the cables can be dried faster when the cables are damp, and sealing pipelines can better prevent the immersion of a small amount of water. If the cable must pass through the floor space, make the cable tray or cable rack as high as possible to the floor plane within the allowed height range, so it is best to keep the water pipe facilities away from areas where the cable is concentrated in a large amount, for example, do not set up a kitchen or toilet near China Telecom or equipment room.

Do not deploy telecommunications or equipment rooms in the basement during cabling system application. If isolation is not possible, consider using racks or cabinets, or creating embankment, water Flow is diverted to areas with less impact. When the cable is damp, the measures to be taken depend on the number of affected cables, the comparison between the replacement cost and the business loss risk of the cable without replacement. The cables that are inlet by capillary reaction through the cable should be directly replaced; cables that are seriously affected by inlet may also need to be replaced.

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