Working Principle of Lightning Protection

AC power lightning protection module is suitable for power supply protection of distribution room, distribution cabinet, switch cabinet, AC and DC power distribution panel, communication, electronics, power, network, energy, railway, highway system, etc. There are outdoor input distribution boxes and floor distribution boxes in buildings, which are used for low voltage (220/380VAC) industrial power grid and civil power grid. Signal lightning arrester is used for overvoltage protection of line intrusion; lightning rod is used for direct lightning protection; in power system, it is mainly used for three-phase power input or output of power supply screen in automation room and main control room of substation.

Formation of Lightning

1. Thunderstorm classification

(1) Front Thunderstorms

Frontal thunderstorms are caused by the fact that when two air masses flow on the surface meet, the cold air mass flows under the hot air mass due to its high density, and forms relative motion on the interface between the two air masses and raises them sharply. The hot air flows form strong rising air column and eddy current, which will form cumulus clouds. At this time, if the temperature of the hot air mass is high enough and the moisture is enough, a huge thunderstorm cloud can be formed.

(2) Thermal Thunderstorms

Hot thunderstorms occur in mountainous areas. Because of the sunshine, the temperature of the hill and its surface rises, and the hot air flows to the sky because of the low density. The temperature of nearby trees, lakes and rivers is lower. The relatively cold air flows around the hill concentrate on the areas with high temperature and low density. At the same time, these air flows to the sky because of the high temperature of the hill surface. Thermal thunderstorms form.

2. Cumulus Cloud Generation Mechanism

(1) Charge effect of water absorption

There is a downward electric field in the atmosphere, which makes the positive and negative ions of the air move downward and upward respectively. Neutral droplets are also polarized in the electric field, with negative charges at the upper end and positive charges at the lower end. When a large water drops falls, its lower end absorbs negative ions and repels positive ions. Because the large water drop drops rapidly, the negative charge on its upper end can not absorb the positive ions above it, so the whole water drop is negatively charged. Small droplets are carried upward by the airflow. The polarized negative charge at the upper end of the droplet will absorb positive ions, so small droplets are positively charged.

(2) Ice-freezing effect of water droplets

It is found that water will be positively charged when it is frozen, while unfrozen water will be negatively charged. Therefore, when the updraft in the ice crystal region of clouds takes away the water above the ice grains, the charge will be separated and charged in different cloud regions.

(3) Water drop breakdown effect

The large residual droplets are positively charged and the minute droplets are negatively charged. This is because there are many electrons on the surface of the droplets.

3. Discharge mechanism of thundercloud

Because of the uneven distribution of charges in clouds and the formation of many charge centers, the electric field intensity between clouds, within clouds and between clouds and the earth is different. The discharge to the ground occurs only when the cloud has the highest field strength to the ground and reaches a certain value. Similarly, when the electric field intensity between clouds reaches a critical value, the Intercloud discharge will also occur. In fact, most of the discharges occur between or within clouds.

The mechanism of thundercloud discharging to the ground: the cloud with a large number of charges produces electrostatic induction to the earth, and the earth induces a large number of heterosexual charges, which forms a strong electric field between the thundercloud and the earth. When the electric field intensity reaches 25-30 kV/cm at a certain place, the thundercloud will generate a pilot discharge to the earth (in a few cases, the lightning leader is emitted from the ground up). When the leader reaches the ground or meets the ground leader, lightning strikes are produced by neutralizing the charge and forming a strong discharge. Discharge usually occurs more than once. The first current is very large and the subsequent lightning current is much smaller.

Working Principle of Lighting Protection 

Lightning protection refers to the protection technology that prevents damage to the building itself or its internal equipment caused by direct lightning or lightning electromagnetic pulse by forming an integrated system to intercept and guide the final discharge into the ground.

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