Lightning Protection Measures And Skills For Industrial Switches

By Author: jothan li
Total Articles: 2
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In the scorching summer, it is not the unbearable heat in summer, but the frequent thunder and lightning that makes the engineers most distressed. Lightning brings great security risks to monitoring equipment, ranging from loss of monitoring images or unstable images, to system paralysis as a whole.

Practical applications show that lightning is the main culprit that causes switch hardware failures and affects the stability of industrial switches. Power failures, port failures, cables, etc. of industrial switches caused by lightning occur from time to time.

Since the key component of an industrial switch is an integrated circuit chip, we should properly prevent lightning damage in specific applications. Lightning protection is a complicated problem. Only by adopting the method of environmental remediation and symptomatic treatment can all elements that are likely to be struck by lightning be removed, so that the threat of lightning damage can be reduced to a minimum. Therefore, industrial switches need to comprehensively implement lightning protection, because if the lightning protection of which side is emphasized, ...
... it can only be called local lightning protection, and local lightning protection has the problem of "congenital deficiency”. Therefore, the lightning protection of industrial switches cannot be biased towards any one party. So how do industrial switches protect against lightning?

1. Select the lightning protection zone inside the building
According to the relevant regulations of the International Electrotechnical Commission IEC1312-1 "Lightning Electromagnetic Pulse Protection", the building is divided into 4 areas: LPZOA area, objects in this area may be directly struck by lightning, and the electromagnetic field in the area is not attenuated; LPZOB area , objects in this area cannot be directly struck by lightning, and the electromagnetic field in the area is not attenuated; in LPZ1 area, objects in this area cannot be directly struck by lightning, and the electromagnetic field in the area may be attenuated; LPZ2 area is a follow-up defense minefield. According to the above zoning principles, the industrial switches should be placed in the LPZ2 area as much as possible to reduce the impact of lightning electromagnetic pulses on the industrial switches.

2. The location of the machine room

The location of the computer room should be determined in combination with the far and near planning of the construction project, as well as the terrain location and other factors. For high-rise buildings, the general practice is to set the computer room in the space below the 4th floor and above the first floor. In humid areas, it is not advisable to set up an industrial switch room on the first floor. However, some units are restricted by conditions and do not set up industrial switches’ rooms according to the above principles. According to the relevant regulations of IEC1312-1 "Lightning Electromagnetic Pulse Protection", the division of the roof of the building in the lightning protection zone belongs to the LPZOB zone, in which the electromagnetic field does not decay, and the industrial switch is greatly affected by the electromagnetic field.

3. Equipotential bonding of industrial switches

The purpose of equipotential bonding of industrial switches is to reduce the potential difference between various metal components and systems in the space requiring lightning protection. It is required that the metal components and systems passing through the junction of each mine protection zone, as well as the metal parts and systems inside a mine protection zone, should be equipotential connected at the junction of the mine protection zone. For example, on the equipotential bonding belt at the junction of LPZO and LPZ1 in the lightning protection zone, all metal conductors entering the industrial switch room should be equipotential connected. In addition, these lines should have SPD installed at the junction of LPZ1 and LPZ2.

4. The grounding system of industrial switches

The grounding of industrial switches includes: DC power grounding; telecommunication equipment chassis or rack shield grounding; metal sheath or shield grounding of inbound communication cables; open wire or cable inbound arrester grounding and signal cable empty pair grounding, etc. In order to do a good job of grounding the industrial switch, some units make an artificial ground pole for the industrial switch. The grounding resistance of the ground pole also meets the requirements of the specification, but the distance between the artificial ground pole and the lightning protection grounding of the building is insufficient due to the limitation of the site. 20m.In order to solve this problem, the usual practice is to connect all the grounds of the industrial switch to the communication grounding device shared by the whole station, and then connect the shared grounding device to the lightning protection grounding of the building to form a combined ground pole. After using the combined ground pole, the grounding device of the communication equipment needs to use a special grounding trunk line, and the cross-sectional area of the trunk line is not less than 25mm2 of multi-strand copper conductors.

5. Wiring method

At present, the transmission network of industrial switches adopts two methods: overhead and buried. Among them, for overhead cables, telephone lines or cables should be buried before entering the house, and the buried length is greater than 2ρ (ρ is the resistivity of the grounding resistance, in Ω*m), and the actual length is greater than 50m.The burial is generally the use of metal armored cables directly buried, or non-metallic shielded cables directly buried through metal pipes. From the point of view of lightning protection, the cable entering the room should be buried under the conditions. The transmission network of the industrial switch should be wired along the dedicated signal cable slot indoors, and avoid laying along the structural column of the building or close to the outer wall; the strong and weak current cables should not be laid in the same slot to reduce interference.

6. Shielding of industrial switches

Shielding of industrial switches (including space and line shielding) In addition to signal lines and power lines, industrial switch rooms should also be shielded by grounding metal doors, windows, ceiling keels and anti-static floors.

7. Measures for shunt and pressure limiting

In terms of power supply, three-level shunt and voltage limiting measures should be adopted to minimize the amplitude of lightning electromagnetic pulses. Therefore, the first level is located in the low-voltage part of the main power distribution room, and a 40kA power supply lightning arrester is installed; the second level is located at the power supply box on the floor, and a 20kA power supply lightning arrester is installed; the third level is located in the industrial switch room. At the switch, install a 10kA power lightning protection box, or install a first-level power lightning protection box in front of the UPS. In terms of signal, the measures of current shunt and voltage limit should also be adopted. First, install a reliable program-controlled industrial switch surge arrester on the trunk line and subscriber line, and install a network surge arrester between the industrial switch and the billing terminal.

Source：http://www.hsindustrialswtich.com