Program-controlled switches with reduced economic losses should be completely protected against lightning

The Programmable switch is still quite common. So I studied the comprehensive Lightning Protection Problem of the programmable switch. Here I will share it with you and hope it will be useful to you. Currently, many organizations have installed programmable switches, and the main component of the programmable switches is the integrated circuit (IC ). The IC anti-interference capability is relatively low. Even the lightning electromagnetic pulse (LEMP) induced by the line can penetrate the IC element. Therefore, programmable switches are prone to lightning strikes.

Most of the components that are damaged are trunk boards, user boards, billing cards, and power supplies. Due to the high value of these mainboards, to reduce economic losses, some users try their best to protect the switch and even insure the entire switch to the insurance company. However, the loss caused by the communication interruption caused by lightning strikes occurs, but it cannot be remedied. Therefore, lightning protection of programmable switches is particularly important. So how should the program-controlled switch be protected against lightning? The author believes that the following aspects should be taken into account comprehensively.

Determine the lightning protection area inside the building (LPZ)

According to the relevant provisions of the International Electrotechnical Commission IEC1312-1 lightning electromagnetic pulse protection, the building is divided into four areas (figure 1): LPZOA area, all objects in the current zone may be directly struck by lightning, and the electromagnetic field in the zone has no attenuation. In the LPZOB zone, the objects in the current zone cannot be directly struck by lightning, and the electromagnetic field in the zone has no attenuation. In the LPZ1 zone, objects in the current area cannot be directly struck by lightning, and the electromagnetic field in the area may degrade. The LPZ2 area is the subsequent lightning protection area. According to the above partition principle, the Programmable switch should be placed in LPZ2 as much as possible to reduce the impact of lightning electromagnetic pulse on the switch.

Determine the equipotential connection of the vswitch

The purpose of equipotential connection of vswitches is to reduce the potential difference between various metal parts and systems in the space that requires lightning protection. It is required that the metal parts and systems passing through the junction of each lightning protection area, as well as the metal parts and systems inside a lightning protection area, should be equipotential connections at the junction of the lightning protection area (figure 1 ). For example, in The equipotential connection band at the junction of LPZO and LPZ1 in the lightning protection area, equipotential connections should be made to all metal conductors entering the switch room. Additionally, SPD should be installed at the LPZ1 and LPZ2 intersections.

Determine the IDC location

The IDC location should be determined by factors such as the distance and proximity planning of the construction project and the terrain location. For high-rise buildings, the general practice is to set the data center in a space above the first floor of the 4-storey or below. In wet areas, the first floor should not have a telephone switch room. However, some units are restricted by the conditions and do not set up switch rooms in accordance with the above principles. For example, the Programmable switch room of Guangdong Ying hotel is located in the basement room on the building. According to the relevant provisions of IEC1312-1 lightning electromagnetic pulse protection, the building area in the lightning protection area is divided into LPZOB area, the electromagnetic field in the area does not decay, the switch is greatly affected by the electromagnetic field.

Determine the grounding system of the switch

The grounding of a program-controlled switch includes: DC power supply grounding; telecommunication equipment housing or rack shielding grounding; metal jacket or shielded grounding of the incoming communication cable; grounding of lightning arresters on open cables or cable entry stations, and grounding of empty cables on signal cables. In order to ensure the grounding of a program-controlled switch, some units make a pair of Artificial Ground poles for the program-controlled switch separately, and the grounding resistance of the ground pole also meets the standard requirements, however, the distance between the Artificial Ground pole and the anti-lightning ground of the building is less than 20 mb due to the limitation of the site. For example, the distance between the yunfu Hotel in Guangzhou and the General Data Center of China South Building is less than 20 mb, does not comply with the national JGJ/T16-92 "Civil Building electrical design specifications" on the Two-site network independence must be greater than 20 m of the relevant provisions. To solve the above problems, the common practice is to connect all the Grounding Devices of the program-controlled switch with the communication Grounding Devices shared by the whole station, and then connect the shared Grounding Devices with the anti-lightning Grounding Devices of the building, build a ground pole. After the ground pole is combined, the grounding device of the communication equipment must use a special grounding trunk line. The cross-sectional area of the trunk line is no less than 25mm2 of the copper wires.

Cabling method

Currently, the transmission network of a vswitch adopts two methods: overhead and overhead. For overhead cables, the telephone lines or cables should be buried before entering the room. The buried length is> 2 P (P is the resistivity of the grounding resistance, in the unit of Ω * m), and the actual length is> 50 m. Generally, metal-clad cables are directly buried, or non-metallic shielded cables are directly buried through metal pipes. From the perspective of Lightning Protection, underground cables should be used in case of conditions. The transmission network of the programmable switch should be cabled along the dedicated signal cable trough in the room to avoid laying along the building structure column or close to the external wall. strong and weak current cables should not be laid along the same trough to reduce interference. For example, if a center in Guangzhou does not have a special signal cable trough, its signal line and power line are laid in the same trough. When the power line is struck by lightning or lightning pulse, it will also sense an electromagnetic pulse on the signal line and transmit it along the signal line to the switch, causing the switch to be struck by lightning. As a result, the switchboard and computer network systems of the central building are often struck by lightning.

Shield A vswitch

In addition to signal lines and power cables, the switch room should also be shielded. The specific method is to ground metal doors, windows, ceiling keel and anti-static floor.

Measures for determining traffic distribution and pressure limit

In terms of power supply, three-level shunt pressure limiting measures should be adopted to minimize the lightning electromagnetic pulse amplitude. Therefore, the first level is located in the low-voltage part of the main power distribution room, And the 40kA power lightning box is installed; the second level is located in the power supply box on the floor, and the 20kA power lightning box is installed; level 3 is located at the power switch of the switch room. A 10kA power lightning box is installed, or a level 1 power lightning box is installed before the UPS. In terms of signal, measures for shunting and pressure limiting should also be adopted. First, install a program-controlled switch lightning arrester with reliable performance on the trunk line and the user line respectively, and install a network Lightning Arrester between the switch and the billing terminal. In short, the program-controlled switch lightning protection should not focus on either side, which side of the lightning protection can only be called local lightning protection, and local lightning protection has a "inherent deficiency" problem. So the program-controlled switch lightning protection should be carried out comprehensively.