Comprehensive lightning protection of modern buildings

1.Grounding device in lightning protection

With the rapid development of my country's national economy, the widespread application of smart devices and electronic information systems has become more and more stringent in the prevention of lightning disasters. The occurrence of lightning disasters often causes and serious consequences for such places. In order to reduce lightning disasters to a minimum, we must enhance the awareness of lightning protection and disaster reduction. The safety inspection of lightning protection devices is especially worthy of our attention. The comprehensive lightning protection of modern buildings includes three parts: direct lightning, lightning induction, and lightning wave intrusion protection. For a complete set of lightning protection facilities, in order to achieve the purpose of protection against different lightning damages, technical measures such as flashover, shunting, shielding, equalization, and grounding must be taken. Therefore, the external lightning protection device should include technical links such as lightning receptors, down conductors, grounding devices, shielding, equipotential bonding, reasonable wiring, and surge protection.

Grounding device in lightning protection

The lightning protection device in the comprehensive lightning protection of modern buildings refers to the sum of air-termination devices, down conductors, grounding devices, surge protectors (SPD) and other connecting conductors. Generally, grounding devices in lightning protection are divided into two categories- external lightning protection devices and internal lightning protection devices. The external lightning protection device consists of an air-termination device, a down conductor and a grounding device, that is, a traditional lightning protection device. The internal lightning protection device is mainly used to reduce the lightning current and its electromagnetic effect inside the building, such as the use of electromagnetic shielding, equipotential bonding and installation of surge protectors (SPD) to prevent possible harm caused by lightning electromagnetic pulses. The grounding device is an important part of the lightning protection device. The grounding device discharges the lightning current to the ground, and limits the voltage of the lightning protection device to the ground from being too high. In addition to independent lightning rods, the grounding device in lightning protection can be shared with other grounding devices on the premise that the grounding resistance meets the requirements.

External lightning protection device

Air-termination

Air-termination is a metal object specially used to receive lightning flashes. The metal pole for flashing is called a lightning arrester, the metal wire for flashing is called a lightning wire or overhead ground wire, and the metal belt and metal net for flashing is called a lightning protection belt or a lightning net. All air-termination devices must be connected to the grounding device through the down conductor. Lightning rods, lightning conductors, lightning nets, and lightning strips are all air-termination devices. They all use their prominence above the protected object to lead the lightning to themselves, and then through the down conductor and grounding device, the lightning current is leaked into The earth, in order to protect the protected objects from lightning strikes. The materials used in the air-termination system should meet the requirements of mechanical strength and corrosion resistance, and should also have sufficient thermal stability to withstand the thermal damage of lightning current.

Lightning rod material

The lightning rod in the comprehensive lightning protection of modern buildings is generally made of galvanized round steel or galvanized welded steel pipe. It is usually installed on a frame, pillar or building, and its lower end is welded to the grounding device through the down conductor. Because the lightning rod is higher than the protected object and is directly connected to the ground, when the thundercloud leader approaches, the electric field strength between it and the thundercloud is the largest, so the path of the thundercloud discharge can be attracted to the lightning rod itself and passed through the downline and The grounding device safely discharges the lightning current to the ground, so that the protected object is not directly struck by lightning. The protection range of the grounding device in lightning protection is represented by the space it can protect against direct lightning strikes.

Overhead ground wire

The lightning line is erected on the overhead line to protect the overhead line or other objects (including buildings) from direct lightning strikes. Because the lightning wire is both overhead and grounded, it is also called overhead ground wire. The principle and function of the lightning rod are basically the same as that of the lightning rod. Lightning protection belts and lightning protection nets are commonly used to protect tall buildings from lightning strikes. Lightning protection belts are generally installed around the roof, 100mm～150mm higher than the roof, and the distance between supporting cards is 1m～1.5m. In addition to installing around the roof, the lightning protection net is also connected vertically and horizontally with round steel or flat steel when needed. The lightning protection belt and the lightning protection net must be reliably connected to the grounding device through the down conductor.

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