What are the interference protection measures for the computer room's integrated wiring system?

1. Types of interference sources

(1) Interference sources from inside the computer room building

• High-frequency interference generated by distribution networks and distribution boxes.
• Harmonic interference generated by sparks in high-power motors.
• Interference caused by fluorescent lamps and electronic ballasts.
• Interference generated by high-frequency switching power supply.
• Interference caused by the ringing current of the telephone.
• Periodic pulse interference generated by information processing equipment.

If the integrated wiring system cannot maintain a safe distance from these interference sources, a shielding system can be used to reduce or eliminate the interference of the above interference sources on the integrated wiring system.

(2) Interference sources from outside the computer room building

The interference sources from outside the computer room building are:

Radar, radio transmitting equipment, mobile phone base stations, high-voltage power lines, electrified railways, interference signals in lightning strike areas, etc.

Obviously, the interference sources outside the intelligent building have a higher electric field strength. When one of the above interference sources exists outside the integrated wiring system, a shielding system should also be used.

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(3) Interference sources from the surrounding environment of the integrated wiring system

When the interference signal field strength of the surrounding environment of the integrated wiring system or the noise level of the integrated wiring system exceeds the following regulations, a shielding system should also be used for protection.

• For computer local area networks, if the frequency of the introduced interference signal is 10kHz~600MHz, its field strength is 1V/m; if the frequency of the interference signal is 600MHz~2.8GHz, its field strength is 5V/m.
• When telecommunication terminal equipment introduces interference signals with a frequency of 15 to 80 MHz through signal DC or AC lead-in lines, the field strength is 3 V/m (amplitude modulation 80%, 1 kHz).
• When the terminal equipment with analog/digital terminal interface provides telephone service, the total bandwidth where the noise level exceeds 40dB should be less than 200MHz.
• The background noise should be at least 12dB lower than the reference level.

2. Anti-interference measures for integrated wiring systems

When the electric field strength of the interference wave emitted by the integrated wiring system exceeds the specified value, the factors that determine whether protective measures are needed are relatively complex, among which the most harmful are electromagnetic interference and electromagnetic radiation. Electromagnetic interference is related to whether the integrated wiring system can work normally; electromagnetic radiation is related to the security of the integrated wiring system in normal operation without the information being stolen by other personnel, or causing electromagnetic pollution.

When designing an integrated wiring system project, careful arrangements and designs must be made and appropriate protective measures must be selected based on the requirements of the construction unit.

(1) Shielding measures to reduce electromagnetic interference

• The metal shell, cable shielding layer and metal wire duct of the information system should be connected to the same potential when introduced into the frame or building. The attenuation calculation of the magnetic field strength should be carried out for the lightning protection zone where the information system is located, and corresponding shielding measures should be taken according to the calculation results.
• The data center should not be located on the high floors of the building, but in the center of the lower floors of the building. The relevant equipment should be as far away from the outer wall of the building as possible. According to the requirements of lightning protection zoning and information equipment, appropriate shielding measures should be taken to attenuate the electromagnetic field generated by lightning strikes to the inner layer.
• When the information equipment has a non-metallic shell and the shielding of the building does not meet the requirements, a metal shielding net or shielding room can be directly installed on the computer room or equipment according to the importance of the information equipment, and the metal shielding net or shielding room can be connected to the equipotential bonding belt.

(2) Shielding measures for outdoor lines

The following points should be noted when shielding outdoor lines.

• Shielded cables should be used in places that require protection, and the two ends of their shielding layers should be connected to the same potential. The shielding layers should also be connected to the same potential where they pass through the boundary of the lightning protection zone.
• When using optical cables containing metal components, all metal components such as metal plugs, metal moisture barriers and metal reinforcement cores should be connected to the same potential at the entrance.
• Cables interconnecting buildings should be laid in metal pipes, and both ends of the metal pipes should be electrically connected and connected to the equipotential bonding belts of each building. The cables in the pipes should also be connected to the equipotential bonding. If there are power and communication cables connected between adjacent buildings, their grounding devices should also be connected together.

(3) Strengthen the anti-interference ability of the wiring system's internal structure and materials

This is mainly a requirement for products that may generate electromagnetic interference and equipment that may be affected by electromagnetic interference. Specific requirements can be tested in accordance with relevant standards during the product manufacturing process.

In general, the appearance structure of computer equipment, communication equipment and electronic equipment should be made of metal boxes, cabinets or racks, so that they can be in the form of Faraday cages, have grounding terminals and be well grounded. This can enhance the anti-interference and anti-radiation capabilities of the equipment to a certain extent.

The selection of cables for the integrated wiring system must also meet the system requirements and be comprehensively considered in combination with the electromagnetic environment around the building. Anti-interference ability and transmission capacity are usually the main considerations, and economic costs must also be considered.

When selecting cables and connection hardware for the integrated wiring system, ensure consistency after determining a certain category. If shielding is selected, the cables and connection hardware must be shielded and have a good grounding system. Twisted pair cables are usually used in the links of the integrated wiring system, and twisted pair cables have the ability to absorb and transmit electromagnetic waves.

(4) Pay attention to the distance between equipment and transmission lines and different interference sources

In addition to using shielding and grounding to improve its anti-interference and anti-radiation capabilities, the integrated wiring system must also be kept as far away from interference sources as possible to reduce their impact on the normal operation of the system, improve the reliability of the system and equipment, and make the integrated wiring system a truly standard and standardized wiring system in the data center.

Through some experiments, we know that when the transmission line is at different distances from the interference source, the degree of distortion of the transmission signal is different. Therefore, during the construction and installation process, we must pay attention to the relationship between the distance between the wiring system and different interference sources, strictly follow the specifications for design and construction, and do the corresponding testing work to ensure the normal and reliable operation of the integrated wiring system.