Lightning protection grounding is a protection against buildings, electrical equipment and facilities in order to shed lightning currents. Safe use of buildings, electrical equipment and facilities is essential. The lightning protection grounding series of buildings is generally divided into lightning rods and lightning protection lines. The grounding of the power system is generally installed and used separately with the lightning protection grounding system to avoid damage to the electrical equipment caused by lightning. For high-rise buildings, in addition to roof lightning protection, there are lightning protection belts for anti-side lightning strikes and grounding devices. Usually, the lightning rods and lightning conductors on the roof are welded to the main reinforcement of the building, and then the grounding body on the ground. Connected to form a lightning protection device for the building, that is, a natural grounding body combined with an artificial grounding body to achieve the best lightning protection effect.
The basic principle of lightning protection
Lightning is a phenomenon of discharge in nature. The saturated water vapor in the atmosphere rises and falls due to the change of climate. During the convection process, due to strong friction and collision, a large number of water droplets gather into the thundercloud with different charges, and the earth will induce the thundercloud The opposite charge. When the electric field strength of the charged cloud block reaches 25~30kVcm, the surrounding air will be broken down, and the thundercloud will break down on the earth. This is the lightning we usually see, and the discharge time is generally 30~50s. Because the lightning rod on the barrier device is at the highest point of the building on the ground, it is easier for the lightning to scatter the lightning current to the earth through the lightning rod and the down-conductor connected to it, thereby protecting the protected building and the like. Direct lightning strikes.
Lightning rods are devices used to protect electrical equipment and tall buildings from direct lightning strikes. Lightning rods actually act as lightning receptors. Because the height of the lightning rod exceeds the protected building, under the thundercloud, its tip has a large electric field, which can first direct the lightning current in the air to the tip and leak into the earth, thus avoiding the place. Thundercloud discharges to the protected object.
Lightning rods are usually made of galvanized round steel or galvanized steel. The diameter of the round steel is generally not less than 8 mm, and the diameter of the steel pipe is generally not less than 25 mm. It is usually installed on poles or frames, chimneys, buildings, and the lower end is welded to the grounding device via the down conductor. The length of the lightning rod is generally not more than 5m.
The installation of the lightning rod down conductor is generally round or flat steel. The specifications of the round steel are not less than 8mm, the thickness of the flat steel is 4mm, and the cross-sectional area is not less than 48mm2.
The lightning rods attached to the chimney are required to have a diameter of not less than 12 mm, a flat steel thickness of 4 mm, and a cross-sectional area of not less than 100 mm2.