The Intrusion Path and Protection Means of Induction Lightning in Intelligent Buildings

May 20, 2022

Intelligent buildings have a high degree of informatization integration, and various electronic equipment chips have low tolerance and are easily harmed by induction lightning. Now, the inspection and acceptance of lightning protection is more careful and strict in the inspection of direct lightning strikes, but relatively less attention is paid to the inspection and acceptance of induction lightning.

Once a lightning strike occurs in a smart building, it may cause a greater loss of equipment. This article introduces the intrusion methods and defense measures of building induction lightning, hoping to help everyone.
1. Intelligent building induction lightning intrusion path.

Induction lightning is usually formed by electrostatic induction or electromagnetic induction and poses a serious threat to low-voltage electronic equipment in buildings. Here are some ways to sense mine intrusion into buildings.

①Intrusion of power supply lines.
Usually, the power of the electronic information system in the building is usually transmitted to the room through the power line, and the power line is easily hit by direct lightning strikes and induced lightning strikes. Once the high-voltage power line is struck by lightning, it is coupled to the 220-volt low-voltage through the transformer, invading the power supply equipment of the building electronic information system; at the same time, the low-voltage line is often affected by direct lightning strikes or induced lightning overvoltage, resulting in strong lightning overvoltage and damage to the building. Electronic Information System.

②The communication line is invaded.
The communication line intrusion of the electronic information system in the building can generally include three situations. First of all, if there are protrusions on the ground around the building, when struck by lightning, the strong lightning voltage will penetrate the nearby soil layer, and the lightning current will directly enter the surface of the cable, and then penetrate the outer skin, causing high voltage to invade the communication line. Second, if a multi-core cable is run in parallel with wires or cables from various different sources, if the wires are struck by lightning, lightning overvoltages from nearby wires are often felt, which can damage the low-voltage electronics of the building. Third, in the process of discharging to the earth, thunderclouds often feel thousands of volts of overvoltage on the line, causing the electronic equipment connected to the line to be damaged by lightning strikes, and intrusion value communication lines through the connection of the equipment. This intrusion method is distributed along the communication line, and has a wide range of influence and great harm.

③ The ground potential counterattack voltage is invaded by the grounding body.
When lightning weather occurs, the strong lightning current will leak to the radioactive potential distribution near the ground grounding area through the grounding body and lead wires. If other grounding bodies connected to electronic equipment are found near, a high-voltage ground potential counterattack will be formed, and the intrusion voltage can reach tens of thousands of volts. The lightning protection device of the building introduces a strong lightning current into the ground, forming a strong magnetic field change around it, and usually induces lightning overvoltage on the adjacent wires (signal line and power line). At this time, the lightning protection device of the building can not only protect the electronic information system, but also And it is likely to introduce lightning current. Therefore, the voltage resistance of the integrated wire chip of the electronic information system is weak, generally not exceeding 100 volts, and a multi-level comprehensive lightning protection system should be established to prevent the intrusion of building induction lightning.
2. Protective measures


Shielding refers to a measure to reduce or prevent electromagnetic interference or overvoltage energy from entering a building with the help of various metal shields.

For the weak current system of buildings, it can generally be divided into building shielding, equipment shielding and various cable shielding. Building shielding can generally be combined with the functions and importance of electronic information equipment and information equipment, summarize and analyze its economic investment, and take appropriate shielding methods.

Generally, building steel bars, metal doors and windows, metal frames, floors, etc. can be effectively welded to form a Faraday cage, and at the same time, the ground net can be effectively connected to form a shielding net. At the same time, the computer room in the building should also be treated with anti-static. The walls can be made of anti-static aluminum plastic panels, which are connected to the shared system of the computer room to form a Faraday cage, which can effectively shield the external electromagnetic field.

As with most modern buildings, many have reinforced concrete structures or all-metal framing. For the shielding of equipment in buildings, it should generally be shielded separately in combination with the use nature of electronic equipment and the electromagnetic environment during lightning strikes.

Electronic information equipment should be effectively connected to the grounding system. For mainframes and electronic equipment, the chassis should be covered before lightning strikes to ensure shielding effectiveness. For cable shielding, such as various power cables, metal pipes and communication lines in buildings, buried entry is required.

The buried horizontal distance is generally more than 15m, and various cables should be shielded. Metal hoses, rigid conduits, trestle bridges, wire textile meshes, etc. can be used as shielded cables. Generally speaking, most inductive lightning strikes occur due to the induced high voltage generated by the transmission line in the alternating magnetic field, which destroys the electronic information system in the building.

Therefore, shielding the transmission line is a reasonable means to avoid or reduce the damage caused by induced lightning strikes.
② Equipotential bonding.

Equipotential bonding is a key part of building induction lightning protection, mainly to greatly reduce the potential difference generated by lightning current, control the lightning electromagnetic field in the building, reduce the damage caused by lightning overvoltage, and ensure that the electronic information equipment in the building can maintain normal operation. .

Building equipotential bonding is mainly to connect wires or surge protectors. Building lightning protection devices are effectively connected to metal frames, metal devices, and external wires to form equipotential bonding to achieve voltage equalization and equipotential bonding to avoid building fires or other safety accidents.

③ Integrated wiring.

When installing electronic information equipment in a building, generally try to avoid the location of strong magnetic field to avoid damage to electronic equipment in a strong magnetic field environment.

For the defense of induction mines, general wiring should be carried out. Since the reinforced concrete column and the entire building shielding network are located on the outer wall, the lightning current generally passes through the regional steel bars to the grounding device, so the current density in the outer wall area is high and the electromagnetic field is also strong. Therefore, the circuit area formed by the power lines and signal lines of building electronic equipment should be It should be as small as possible and cannot be parallel to the wall lightning protection system to avoid the generation of large circuit induced potential and damage to electronic equipment.

In addition, various electrical feeders entering the building should be protected with metal pipes or double shielded cables.

④Install the lightning protection device.

Corresponding lightning arresters should be installed on the power lines and signal lines entering and leaving the building to discharge the surge energy that invades the building along the line.

The power supply system can adopt three-level lightning protection, install a first-level surge protector in the main power distribution cabinet, and install a second-level power supply lightning protection device in the floor power distribution cabinet.

The signal system can install other signal lightning protection devices such as network lightning protection device and telephone lightning protection device for network signal lines and telephone lines.
3. Conclusion
Compared with the randomness of direct lightning strikes, the frequency of inductive lightning strikes is more frequent, and the probability of causing damage to equipment is also greater, so lightning protection needs to be done for smart buildings. Strengthen the lightning protection capability of buildings by means of shielding, equipotential bonding, and installation of lightning protection devices.