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Introduction to direct lightning and induction lightning, and lightning strike ways



# Direct lightning:Thunder and lightning directly strike electrical equipment, lines, buildings and other objects.

Sometimes the thundercloud is very low, and there are no thunderclouds with opposite charges around, so it is possible to induce the opposite charge on the ground protrusions, forming a large lightning field between the thundercloud and the earth. When the electric field strength between the thundercloud and the ground reaches 25~30kV/cm, the discharge begins, which is a direct lightning strike.

According to observations, most of the thunderclouds that produce lightning strikes on the ground are negative thunderclouds.

# Inductive lightning: Overvoltage caused by electrostatic induction or electromagnetic induction of lightning on lines, equipment or other objects. The induced overvoltage on overhead lines can reach tens of thousands or even hundreds of thousands of volts, which is very harmful to the power supply system.

The intensity of lightning activity and the law of direct lightning

Thunderstorm day: As long as there has been thunder and lightning activity (including seeing thunder flashes and hearing thunder) in a day, it is considered a thunderstorm day.

1) Areas where the average annual thunderstorm days are less than 15 days are areas with less thunderstorms;
2) Areas where the average annual thunderstorm days exceed 40 days are areas with heavy thunderstorms;
3) Areas where the average annual thunderstorm days exceed 90 days are areas with particularly intense lightning activity.

The law of thunder and lightning activity

1. Hot and humid areas have more thunderstorms than cold and dry areas, and mountain areas are larger than plain areas, plain areas are larger than desert areas, and land arears are larger than lake and sea areas.

2. The formation of lightning zone is related to factors such as geological structure (ie soil resistivity), facilities on the ground and geographical conditions.

1) Places with low soil resistivity are prone to lightning strikes;
2) It is easy to be struck by lightning at the junction of soils with different resistivities;
3) The east and south slopes of the mountain are more prone to lightning strikes than the north and west slopes of the mountain;
4) Mountain areas are vulnerable to lightning strikes.

3. The lightning strike position of a building is related to factors such as the height, length and roof slope of the building.

The main way of lightning strike

Ways for lightning strikes to invade buildings and equipment

1) Lightning strikes buildings (direct lightning)
2) Lightning strikes overhead conductors (direct lightning)
3) Lightning electromagnetic induction
4) Ground potential counterattack
5) Operating overvoltage

The damage channel of lightning strikes summarizes the damage channel of other surges.

1. Lightning strikes buildings

2. Lightning strikes overhead conductors

3. Lightning electromagnetic induction

4. Ground potential counterattack

The main way of lightning strike

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