The outdoor door of the building is more likely to be struck by lightning, causing great inconvenience to the user and also causing great economic losses. Through the investigation and analysis of the causes of these lightning strikes, the main components of the crash are the power box, circuit board, and talker.
The main route to lightning strikes
(1) Directly hit mine. Direct lightning strikes lightning directly on the object, and thunderclouds near the ground induce opposite charges on the protrusions.
When the electric field strength between the thundercloud and the ground protrusion reaches the air breakdown strength, a breakdown discharge will occur. This thundercloud direct breakdown discharge on the ground protrusion is called a direct thunderbolt. High buildings and their sides are subject to direct lightning strikes, and direct lightning strikes on the side of a building can be called side impact mines.
(2) Induction of thunder. Lightning strikes a conductor, such as a metal object next to the device, and indirectly strikes the object. Lightning induction is divided into electrostatic induction and electromagnetic induction. The formation of electrostatic induction is due to the induction of a large number of opposite charges on the top of ground projections when the cloud approaches the ground. When the thundercloud and other thunderclouds or other objects are discharged, the accumulated charge on the top of the protrusion suddenly loses its bondage, showing a high voltage and rapidly propagating in the form of lightning waves. The formation of electromagnetic induction is due to direct lightning currents that produce a rapidly changing strong magnetic field in the surrounding space, which induces high voltages in nearby metals. Induction mines are not as violent as thunder but they are much more likely to occur than direct thunder. Because direct lightning strikes only when lightning strikes the ground, it will cause disasters to the ground. Induction lightning, however, strikes lightning regardless of the lightning strikes on the ground, or lightning strikes between thunderclouds may occur and cause disasters. A lightning stroke can occur in a relatively large range and multiple small parts at the same time, and this induced high voltage can be transmitted far through the signal wires, power lines, telephone lines and other metal wires, resulting in lightning The scope has expanded.
Access control Intercom System lightning protection installation
The following measures should be taken to prevent the above major lightning strikes:
1. The installation position of the power box should be properly selected.
(1) Avoid installing on the side wall of the house, especially on the side wall of the projected house, so as to prevent direct lightning strikes.
(2) Avoid installation on the side of a pipe where there is a metal pipe, a gas pipe, etc. Especially, the same side wall that is less than 5 meters from the metal pipe and the air pipe can not be installed.
2. Both the power box and the circuit board should be grounded. The grounding wire should be solid and reliable, and the grounding resistance should be ≤ 0.1Ω.
3, wiring should be correct and reasonable. Power lines and signal lines should be placed indoors to avoid outdoor wiring as much as possible, avoiding the same direction and cross wiring as metal pipes, air pipes, etc., and it is impossible to avoid wiring in the same direction as metal pipes, gas pipes, etc. The distance between the two should be ≥ 5 meters. . The wiring should be laid in a straight line to minimize bending wiring.
4. The power source of the power box should be connected to the power socket. When weather is prevented or weather changes may cause lightning, it is convenient to cut off the power in time to prevent lightning strikes.
October 19, 2022
