Summary of industrial switch lightning protection knowledge
2019/12/11 18:02:59
1. select the lightning protection area inside the building
According to IEC1312-1 "protection of lightning electromagnetic pulse" of International Electrotechnical Commission, the building is divided into four areas: lpzoa area, objects in this area may be directly struck by lightning, and the electromagnetic field in this area is not attenuated; lpzob area, objects in this area are not likely to be directly struck by lightning, and the electromagnetic field in this area is not attenuated; lpz1 area, objects in this area are not likely to be directly hit by lightning The electromagnetic field in the area may be attenuated due to lightning stroke; lpz2 area is the follow-up lightning protection area. According to the above zoning principle, the industrial switch should be placed in lpz2 area as much as possible to reduce the impact of lightning electromagnetic pulse on the industrial switch.
2. Equipotential connection of industrial switch
The purpose of equipotential connection of industrial switch is to reduce the potential difference between various metal parts and systems in the space requiring lightning protection. It is required to make equipotential connection at the junction of lightning protection area for the metal parts and systems passing through the junction of lightning protection areas and the metal parts and systems inside a lightning protection area. For example, equipotential connection shall be made on the equipotential connection belt at the junction of lpzo and lpz1 in the lightning protection area to all metal conductors entering the industrial grade switch room. In addition, SPD shall be installed for these lines at the junction of lpz1 and lpz2.
3. location of machine room
The location of the machine room shall be determined by combining 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 machine room in the space below the fourth floor and above the first floor. In humid areas, industrial grade switch rooms should not be set on the first floor. However, some units are limited by the conditions and do not set up industrial grade exchange rooms according to the above principles. For example, the program-controlled industrial grade exchange rooms of Guangdong Yingbin Hotel are set up in the extra floor rooms on the roof of the building. According to the relevant regulations of IEC1312-1 protection of lightning electromagnetic pulse, the building roof is divided into lpzob area in the lightning protection area, where the electromagnetic field is not attenuated, and the industrial switch is greatly affected by the electromagnetic field.
4. Grounding system of industrial switch
The grounding of industrial grade switch includes: DC power supply grounding; telecommunication equipment shell or rack shielding grounding; metal sheath or shielding grounding of inbound communication cable; open line or cable inbound lightning arrester grounding and signal cable empty line pair grounding, etc. In order to do a good job in the grounding of industrial grade switches, some units make a pair of artificial earth electrodes for industrial grade switches separately, and the earth resistance of the earth electrodes also meets the requirements of the specification, but the distance between the artificial earth electrode and the lightning protection earth of the building is less than 20 m due to the limitation of the site. For example, the distance between the artificial ground electrode and the lightning protection ground of the general machine room of Guangzhou Yunfu Hotel and South China building is less than 20 m, which does not conform to the relevant provisions of the national JGJ / t16-92 code for electrical design of civil buildings that the distance between the two networks must be greater than 20 m when they are independent. In order to solve the above problems, the common method is to connect all the grounding of the industrial switch with the communication grounding device shared by the whole station, and then connect the shared grounding device with the lightning protection grounding of the building to form a combined grounding electrode. After the combined grounding electrode is adopted, the grounding device of the communication equipment shall adopt the special grounding trunk line, and the cross-sectional area of the trunk line shall not be less than 25mm2 multi stranded copper conductor.
5. wiring method
At present, the transmission network of industrial grade switch adopts two methods: overhead and underground. For the overhead cable, the telephone line or cable shall be buried before entering the room, with the buried length > 2 ρ (ρ is the resistivity of the grounding resistance, unit: Ω * m), and the actual length > 50m. Generally, the metal armored cable or the non-metal shielded cable are directly buried through the metal pipe. From the point of view of lightning protection, the cable entering the room should be buried under certain conditions. The transmission network of industrial switch shall be laid indoors along the special signal cable trough to avoid laying along the structural column of the building or close to the external wall; the strong and weak current cables shall not be laid in the same trough to reduce interference. For example, a central building in Guangzhou does not have a special signal cable trough, and its signal line and power line are laid in the same trough. When the power line is hit by lightning or induced lightning electric pulse, an electromagnetic pulse will also be induced on the signal line, and it will be transmitted to the industrial switch along the signal line, so that the industrial switch is hit by lightning. As a result, the central building's switchboard and computer network system are often struck by lightning.
6. shielding of industrial switch
In addition to the signal line and power line, the industrial switch room should also be shielded. The specific method is to ground the metal door, window, ceiling keel and anti-static special floor.
7. Measures for shunt and pressure limit
In terms of power supply, three-stage shunt voltage limiting measures should be adopted to minimize the amplitude of lightning electromagnetic pulse. Therefore, the first level is set in the low-voltage part of the main power distribution room, with a 40ka power lightning box installed; the second level is set in the power box of the floor, with a 20KA power lightning box installed; the third level is set in the power switch of the industrial grade switching room, with a 10kA power lightning box installed, or a first level power lightning box installed in front of the ups. In the aspect of signal, the measures of shunt and pressure limiting should also be adopted. Firstly, the lightning arrester of program-controlled industrial switch with reliable performance is installed in trunk line and subscriber line respectively, and the network lightning arrester is installed between industrial switch and billing terminal.
Tag: industrial ethernet switch
lightning protection
surge protector
