How to do a good job in waterproofing and lightning protection for explosion-proof cameras with frequent thunderstorms?
With the arrival of the thunderstorm season, the harm caused by adverse weather has caught explosion-proof monitoring equipment off guard. So how to keep explosion-proof monitoring equipment in good condition during extreme thunderstorm weather?
In the application of explosion-proof video surveillance systems, explosion-proof cameras are distributed in various front-end environments, with outdoor cameras accounting for a large proportion. Due to various weather factors, outdoor cameras often need to have functions such as infrared night vision, waterproofing, anti fog, rain and snow protection, etc. When encountering rainstorm, it is particularly important for the monitoring equipment to take precautions in advance.
During the operation of explosion-proof cameras, there is a large temperature change, which can easily cause water mist, especially in rainy seasons. The formation of fog and frost is due to the saturation of temperature and humidity in the air, and water vapor condenses when it encounters cold. Due to the strong and weak low-temperature environment, it condenses into frost and fog respectively. The camera works in environments with high humidity and dust, and the window glass of the protective cover is prone to dirt, which can block the light entering the camera and cause the lens to be blurry and unable to capture objects clearly, directly affecting the video capture effect. You can add wipers on the protective cover to clean the glass by controlling the wipers. To solve the problem of fog and dirt on the camera.
How to improve the sealing performance? It is possible to add a waterproof rubber cover and a water pad at the interface, which has an ideal effect; Applying waterproof adhesive at the screw port of the wiring can enhance waterproofing; The infrared waterproof camera adopts an aluminum alloy shell to improve the accuracy of the interface, and is bonded with high-quality silicone material, resulting in ideal results.
Rainstorm is often accompanied by lightning. Modern security system equipment is basically electronic products, which are very sensitive to lightning overvoltage, electrostatic discharge, electromagnetic radiation and other hazardous factors, and are vulnerable to damage. Video surveillance systems are often prone to injury during thunderstorms. According to data from a safety monitoring center in Beijing, over 80% of lightning disasters in recent years have been caused by damage to internal equipment, including electrical appliances, video surveillance systems, and probes.
Generally speaking, the front-end cameras of explosion-proof video monitoring systems are mostly installed outdoors in relatively open areas, with a high risk of lightning strikes. They are very sensitive to electromagnetic interference such as lightning overvoltage, transient overvoltage in power systems, and electrostatic discharge, making video monitoring system equipment extremely vulnerable to lightning overvoltage damage, causing the entire closed-circuit television video monitoring system to malfunction. However, some residential areas do not have lightning protection design for video surveillance probes, intercom systems, and other facilities, making it easy for induction lightning to take advantage of the situation and destroy the system.
There are various reasons why lightning protection cannot be popularized in practical applications. On the one hand, many party A have insufficient understanding of system lightning protection and are not aware of the importance of lightning protection design for the entire system, which is limited by the engineering cost; On the other hand, some engineering companies do not attach great importance to the lightning protection of the system, because if these requirements are considered, it will increase the project quotation and affect the price advantage during bidding; In this way, there will be significant risks to the security and effectiveness of the system.
Not only outdoor cameras can be damaged by lightning, but equipment in the video surveillance center computer room can also be "damaged" due to lightning attacks. So, how do explosion-proof monitoring equipment prevent lightning? Generally speaking, the explosion-proof video monitoring system is divided into several parts: front-end camera, intermediate transmission, and back-end video monitoring center.
The installation location of front-end explosion-proof cameras is often divided into indoor and outdoor locations. Explosion proof 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 for the input and output ports of the equipment.
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.
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 voltage limiting protection circuits for equipment input and output ports.