1. Lightning protection of front-end equipment

The installation position of front-end cameras often has indoor and outdoor distinction. Cameras installed indoors generally do not suffer from direct lightning strikes. However, lightning overvoltage may also cause damage to the camera, and outdoor equipment needs to consider preventing direct lightning strikes.

Usually, front-end devices such as explosion-proof cameras are placed within the effective protection range of lightning arresters (lightning rods or other lightning conductors). When the explosion-proof camera is installed independently, in order to prevent transient high potential on the lightning rod and down conductor, it is best to keep the lightning rod 3-4 meters away from the camera.

In addition, to prevent electromagnetic induction, the camera power line and signal line led along the power pole should be threaded into a metal tube to achieve shielding effect, and both ends of the shielding metal tube should be grounded.

Cable lightning induced electromotive force is a high-frequency alternating voltage, located in the middle of the cable. Based on this feature, the basic method of protecting against induced lightning is to set up a "voltage limiting protection circuit" at the input and output ports of the equipment.

2. Lightning protection of transmission lines

For analog systems, their circuits mainly consist of transmission signal lines and power lines. The power supply for outdoor explosion-proof cameras can be introduced from terminal equipment or from power sources near monitoring points. Control signal transmission lines and alarm signal transmission lines generally use shielded flexible wires with reinforced cores, which are installed (or laid) between the front end and the terminal. Both ends of the reinforced core and the shielding layer should be well grounded.

According to regulations, when laying transmission lines in urban suburbs or rural areas, direct burial laying can be used. When conditions do not permit, communication pipelines or overhead methods can be used. From the perspective of lightning protection, the direct burial laying method has the best lightning protection effect, and overhead lines are most susceptible to lightning strikes, with high destructive power and a wide range of impact. To avoid damage to equipment at the head and tail ends, grounding treatment should be carried out on each pole during transmission of overhead lines. The suspension lines of overhead cables and the metal pipes in the overhead cable lines should be grounded.

In addition, buried transmission lines cannot prevent lightning strikes from occurring. Numerous facts show that lightning strikes cause faults in buried cables, accounting for about 30% of the total faults. Even in places far away from lightning strikes, some lightning currents still flow into the cables.

Therefore, if cables with shielding layers or cables buried in steel pipes are used, attention should be paid to maintaining electrical connectivity of the steel pipes, which is very effective in protecting against electromagnetic interference and induction. This is mainly due to the shielding effect of metal pipes and the skin effect of lightning currents. Of course, if it is difficult for the cable to pass through metal pipes throughout the entire process, it can be buried and introduced through metal pipes before the cable enters the terminal and front-end equipment, but the buried length should not be less than 15 meters. At the entrance end, the metal outer skin and steel pipe of the cable should be connected to the lightning protection grounding device.

3. Lightning protection of video surveillance center

In video surveillance systems, the video surveillance center is often the place where video surveillance recordings are processed, so its lightning protection is also particularly important. Simply put, the lightning protection of video surveillance centers should include direct lightning protection, lightning protection against electromagnetic wave intrusion, and setting up "voltage limiting protection circuits" for equipment input and output ports.
In terms of direct lightning protection, the building where the video surveillance center is located should have lightning rods, lightning strips, or lightning protection nets to prevent direct lightning strikes. When overhead cable lines are directly introduced, lightning arresters should be installed at the entrance and a "voltage limiting protection circuit" should be set up.