It is generally considered from several aspects.
1 First of all, to determine the quality of building lightning protection facilities According to the relevant provisions of GB50057-94 "Lightning Protection Design Code for Buildings", the program-controlled switchboard building must have anti-radar facilities. When the building height exceeds 30m (a type of lightning protection), 45m (type II lightning protection), and 60m (type III lightning protection), the metal objects such as railings, doors, windows, and lightning protection devices on the outer walls of the above height shall be installed. connection. In addition, the grounding resistance of lightning protection facilities should also meet the requirements of relevant regulations.
2 Identify the interior mine protection zone (LPZ)
According to the relevant provisions of the International Electrotechnical Commission IEC 1312-1 "Protection of Lightning Electromagnetic Pulses," the building is divided into four areas (Figure 1): LPZOA area, where objects in the area may be directly struck by lightning. No attenuation; in the LPZOB area, no direct lightning strikes on objects in the area can occur, and the electromagnetic field in the area is not attenuated. In the LPZ1 area, objects in the area cannot be directly struck by lightning, and the electromagnetic field in the area may be attenuated. LPZ2 area is a follow-up mine protection area. According to the above partition principle, program-controlled switches should be placed in the LPZ2 area as much as possible to reduce the impact of lightning electromagnetic pulses on the switch.
3 The purpose of determining the equipotential bonding of the equipotential bonding switch of the switch is to reduce the potential difference between various metal components and systems in the space where lightning protection is required. Metal parts and systems that pass through the boundaries of lightning protection zones, as well as metal components and systems inside a lightning protection zone, are required to make equipotential bonding at the intersection of the lightning protection zone (Figure 1). For example, in the equipotential bonding zone at the junction of the lightning protection zone LPZO and LPZ1, all metal conductors that enter the exchange room should be equipotentially connected. In addition, SPD should be installed at the junction of LPZ1 and LPZ2.
4 Determine the location of the engine room The location of the engine room should be determined by factors such as the distance and near planning of the construction project, and the location of the terrain. For high-rise buildings, the general practice is to locate the engine room above the first floor below the fourth floor. In wet areas, telephone exchange rooms should not be provided on the first floor. However, some units are subject to conditions and are not based on the above principle to set up the exchange room. For example, the program-controlled exchange room of the Guangdong Yingbin Hotel is located in the additional floor of the building. According to the relevant provisions of IEC 1312-1 “Protection of Lightning Electromagnetic Pulses,†the division of the building’s sky surface in the lightning protection zone is LPZOB zone, where the electromagnetic field is not attenuated and the switch is greatly affected by the electromagnetic field.
5 Confirm the grounding of the switch System-controlled switch grounding includes: DC power grounding; telecommunications equipment chassis or chassis grounding; metal sheathing or grounding of inbound communication cables; grounding or cable inbound arrester grounding and signal cable empty pairs Grounding and so on.
6 Determining the method of wiring At present, the transmission network of the switch adopts overhead and buried methods in the outdoors. Among them, the aerial cable should be buried in the ground before entering the room. The buried length should be greater than 2Ï (Ï is the resistivity of the grounding resistance, and the unit is Ω*m). The actual length is more than 50m. The buried ground is generally directly buried with metal armored cable, or the non-metallic shielded cable is buried directly in the metal pipe. From the standpoint of lightning protection, buried cables should be selected in the case of conditions.
7 In addition to the signal line and the power line, the switch room (including space and lines) should also handle the switch room. The specific method is to ground the metal doors, windows, ceiling keel, and special anti-static floor.
8 Measure for determining the voltage limitation of the shunt On the power supply side, a three-stage shunt limiting device should be used 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 80KA power supply lightning protection box is installed; the second level is located in the power supply box of the floor and the 40kA power supply lightning protection box is installed; the third level is set in the power switch of the switch room. Place a 10kA power supply lightning protection socket. In terms of signals, it is also necessary to use shunt limiting measures. First, install a PT-DB25/DB15/DB9 surge arrester with reliable performance on the trunk and subscriber lines, and install a lightning arrester between the switch and the accounting terminal. In short, the lightning protection of program-controlled switches should not be biased towards any party. The emphasis on lightning protection of one side can only be called partial lightning protection, while partial lightning protection has the problem of “congenitally deficientâ€. So program-controlled switches should be integrated lightning protection.
1 First of all, to determine the quality of building lightning protection facilities According to the relevant provisions of GB50057-94 "Lightning Protection Design Code for Buildings", the program-controlled switchboard building must have anti-radar facilities. When the building height exceeds 30m (a type of lightning protection), 45m (type II lightning protection), and 60m (type III lightning protection), the metal objects such as railings, doors, windows, and lightning protection devices on the outer walls of the above height shall be installed. connection. In addition, the grounding resistance of lightning protection facilities should also meet the requirements of relevant regulations.
2 Identify the interior mine protection zone (LPZ)
According to the relevant provisions of the International Electrotechnical Commission IEC 1312-1 "Protection of Lightning Electromagnetic Pulses," the building is divided into four areas (Figure 1): LPZOA area, where objects in the area may be directly struck by lightning. No attenuation; in the LPZOB area, no direct lightning strikes on objects in the area can occur, and the electromagnetic field in the area is not attenuated. In the LPZ1 area, objects in the area cannot be directly struck by lightning, and the electromagnetic field in the area may be attenuated. LPZ2 area is a follow-up mine protection area. According to the above partition principle, program-controlled switches should be placed in the LPZ2 area as much as possible to reduce the impact of lightning electromagnetic pulses on the switch.
3 The purpose of determining the equipotential bonding of the equipotential bonding switch of the switch is to reduce the potential difference between various metal components and systems in the space where lightning protection is required. Metal parts and systems that pass through the boundaries of lightning protection zones, as well as metal components and systems inside a lightning protection zone, are required to make equipotential bonding at the intersection of the lightning protection zone (Figure 1). For example, in the equipotential bonding zone at the junction of the lightning protection zone LPZO and LPZ1, all metal conductors that enter the exchange room should be equipotentially connected. In addition, SPD should be installed at the junction of LPZ1 and LPZ2.
4 Determine the location of the engine room The location of the engine room should be determined by factors such as the distance and near planning of the construction project, and the location of the terrain. For high-rise buildings, the general practice is to locate the engine room above the first floor below the fourth floor. In wet areas, telephone exchange rooms should not be provided on the first floor. However, some units are subject to conditions and are not based on the above principle to set up the exchange room. For example, the program-controlled exchange room of the Guangdong Yingbin Hotel is located in the additional floor of the building. According to the relevant provisions of IEC 1312-1 “Protection of Lightning Electromagnetic Pulses,†the division of the building’s sky surface in the lightning protection zone is LPZOB zone, where the electromagnetic field is not attenuated and the switch is greatly affected by the electromagnetic field.
5 Confirm the grounding of the switch System-controlled switch grounding includes: DC power grounding; telecommunications equipment chassis or chassis grounding; metal sheathing or grounding of inbound communication cables; grounding or cable inbound arrester grounding and signal cable empty pairs Grounding and so on.
6 Determining the method of wiring At present, the transmission network of the switch adopts overhead and buried methods in the outdoors. Among them, the aerial cable should be buried in the ground before entering the room. The buried length should be greater than 2Ï (Ï is the resistivity of the grounding resistance, and the unit is Ω*m). The actual length is more than 50m. The buried ground is generally directly buried with metal armored cable, or the non-metallic shielded cable is buried directly in the metal pipe. From the standpoint of lightning protection, buried cables should be selected in the case of conditions.
7 In addition to the signal line and the power line, the switch room (including space and lines) should also handle the switch room. The specific method is to ground the metal doors, windows, ceiling keel, and special anti-static floor.
8 Measure for determining the voltage limitation of the shunt On the power supply side, a three-stage shunt limiting device should be used 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 80KA power supply lightning protection box is installed; the second level is located in the power supply box of the floor and the 40kA power supply lightning protection box is installed; the third level is set in the power switch of the switch room. Place a 10kA power supply lightning protection socket. In terms of signals, it is also necessary to use shunt limiting measures. First, install a PT-DB25/DB15/DB9 surge arrester with reliable performance on the trunk and subscriber lines, and install a lightning arrester between the switch and the accounting terminal. In short, the lightning protection of program-controlled switches should not be biased towards any party. The emphasis on lightning protection of one side can only be called partial lightning protection, while partial lightning protection has the problem of “congenitally deficientâ€. So program-controlled switches should be integrated lightning protection.
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