How does the security monitoring prevent lightning strikes? In order to be able to accurately and effectively solve the lightning protection scheme of the security monitoring system, we must first understand the system composition of the security monitoring system accurately, and then accurately analyze the main reasons for the damage to the security monitoring system and the possible lightning overvoltage Way of invasion. So, how does security surveillance prevent lightning strikes?
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How Security Monitoring Prevents Lightning Strikes: Overview of Security Monitoring System Composition, Classification, and Lightning Protection
　 1. Composition of security monitoring system
The security monitoring system is generally composed of the following three parts: the front part: mainly composed of black and white (color) cameras, gimbals, protective covers, brackets, etc. Transmission part: use coaxial cable, electric wire, multi-core wire, adopt overhead, underground or laying along the wall to transmit audio, video, control signals and AC and DC power. Terminal part: It is mainly composed of control equipment, screen splitter, monitor, video storage equipment, etc.
2. Classification of security monitoring system
Classified according to the transmission method of the transmission part, the security monitoring system is mainly divided into the following categories:
A. Coaxial cable transmission monitoring system: Lightning protection focuses on line interface protection at both ends of the transmission cable and protection of the transmission cable itself;
B. Twisted-pair transmission monitoring system: Lightning protection focuses on front-end and terminal power protection and twisted-pair interface protection;
C. Optical cable transmission monitoring system: Lightning protection focuses on the protection of power supply at the front end and the terminal and the shielding of the optical cable's own shielding armor and reinforcement;
D. Microwave transmission monitoring system: The focus of lightning protection is on the direct strike protection of the wireless devices at the front and back stations.
How to Prevent Lightning Strikes in Security Monitoring: Points, Frequently Asked Questions and Precautions of Lightning Protection Solutions for Security Monitoring System
1. Lightning protection
Lightning strikes the camera in the open air and directly damages the device; lightning strikes directly on the cable, causing the cable to fuse and damage. Direct lightning protection is an indispensable foundation for lightning protection and an integral part of lightning protection.
(1) Direct lightning protection for front-end equipment
There are two types of front-end equipment for the security monitoring system: outdoor and indoor. Equipment installed indoors generally will not be subject to direct lightning strikes, while equipment installed outdoors is mostly in a relatively open area, and the risk of direct lightning strikes is greater, you must consider direct lightning protection. problem.
The front-end equipment of the security monitoring system, such as the camera, should be placed within the effective protection range of the lightning receptor (lightning rod or other lightning conductor). For front-end equipment that is already within the protection scope of other air-termination systems or the original air-termination system of high-rise buildings, direct lightning protection may not be considered separately; for front-end equipment that is not within the protection scope of any air-termination system, all Consideration should be given to direct lightning protection. From a technical and economic point of view, it is not feasible to install a separate lightning rod for front-end equipment for direct lightning protection. Generally, a lightning rod is set up on the support rod of the camera. The down conductor can directly use the metal rod itself (also Φ8 galvanized can be used) Round steel or 30 × 3 galvanized flat steel), but in order to prevent electromagnetic induction, the power and signal wires of the camera led along the pole should be laid through metal pipes, and the metal pipes should be reliably grounded.
(2) Direct lightning protection for transmission lines
In order to prevent the transmission line from being hit by direct lightning, the transmission line should be avoided as far as possible, and buried as far as possible through a metal pipe, and both ends of the metal pipe should be reliably grounded.
(3) Direct lightning protection for terminal equipment
The building where the terminal equipment room (commonly referred to as the monitoring room) should be protected against direct lightning strikes. Round steel bars of φ10 (silver paint) can be used to build lightning protection belts on the top of the building, and 3.1.3 terminal equipment for direct lightning protection terminal equipment The room where the computer room (generally called the monitoring room) is located should be protected against direct lightning strikes. Round steel bars of φ10 (silver powder paint) can be used to build lightning protection belts on the roof. In addition, round steel bars of φ10 are used to support the lightning protection belts. The support height is 15 cm. , Set a support every 1m, and use 40 × 4mm galvanized flat steel as the down conductor to connect to the ground network (the resistance of the ground network should be less than 10Ω), and the distance between the down conductors should not be greater than 25 meters. You can also use a lightning rod as a measure to prevent direct lightning strikes, and use 40 × 4mm galvanized flat steel as a down conductor to connect to the ground network. The height and installation position of the lightning rod should be calculated according to the rolling ball method.
2. Lightning protection grounding system
All lightning protection systems should have reliable and effective grounding. The grounding system is also part of the lightning protection. The front end of the security monitoring system and the terminal equipment should have good lightning protection grounding, and the corresponding grounding system should meet the requirements of the specification. Generally, the front-end equipment independent of the building where the monitoring room is located must be independently grounded. However, it is important to point out here:
Regardless of the grounding system of the front end or the terminal equipment, if the distance is less than 20 meters, an equipotential connection should be made between the two grounding systems.
3. Attentions for laying along the wall
Many wiring personnel, because of limited knowledge of lightning protection, or simple and convenient drawings, are accustomed to bundling outdoor wiring lines with building lightning protection strips and down conductors. Convenient for the construction and aesthetics of the project, it also brings a large hidden danger of lightning protection. This is worthy of attention and attention. In order to reduce the risk of lightning damage, any wire / metal line should be avoided from being bundled in parallel with the direct lightning protection system as far as possible, and should be in accordance with the requirements of relevant regulations.
4. Selection of AC power lightning arrester
Effective lightning protection is provided for all AC power input terminals of the security monitoring system. And it should be ensured that the building where the equipment is located has a good lightning protection grounding system, and it is further confirmed whether the lightning protection device of the building is properly used. Corresponding power lightning arresters should be installed at the AC power inlet of the front-end equipment. Considering that the power supply system of the security monitoring system is generally not very standardized, there are usually several volts, dozens of volts between zero and ground, and sometimes even tens of volts. In addition, when installing single-phase power supply lightning protection Installers generally do not pay attention to distinguishing between zero and live wires. In view of this situation, we recommend that when using single-phase power lightning arresters, try to avoid using 1 + NPE protection mode products, because if there is AC on the NPE module, The presence of voltage will generate power frequency freewheeling when the NPE module operates, making it difficult for the NPE module to extinguish the arc and causing the NPE module to burn out. Three levels of protection should be considered for the power cables entering the monitoring equipment room. A first-level lightning arrester can be installed at the power supply line of the main distribution room of the building, and two can be installed at the power supply line of the distribution box on the floor of the monitoring room. Three-level power lightning arrester, install three-level power lightning arrester at the power supply line of the important equipment in the monitoring room. In the case of high zero and ground voltage, it is not recommended to use 3 + NPE or 1 + NPE protection mode power protection. Thunder device. All lightning arresters should be reliably grounded.
5. Transmission line protection of security monitoring system
Statistical data indicate that more than 80% of lightning accidents in security monitoring systems are caused by lightning intrusion wave overvoltages induced on the lines connected to the system. Therefore, the protection of the line connected to the system is an important part of the overall lightning protection that cannot be ignored.
The safe wiring method should be laid through the metal pipe to bury the ground. At the same time, please also note that the two ends of the metal pipe must be effectively grounded. A transmission line laid through a metal pipe buried in the ground can attenuate the amplitude of the lightning intrusive wave to a considerable extent, thereby reducing the probability that the equipment will be damaged by the lightning intrusive wave. In actual engineering, in many cases, when conditions are not allowed, you can run through the metal pipe for overhead wiring; or do not run through the metal pipe for the whole process, but before the cable enters the monitoring room and front-end equipment, it must be buried under the metal pipe. Not less than 15 meters, effectively connect the cable's metal sheath, metal pipe and lightning protection ground at the entrance end. Lightning arresters should be installed at both ends of all transmission lines.
6. Protection of optical fiber communication lines
Generally speaking, the optical fiber line does not need to be equipped with lightning surge protection, because the optical fiber line itself is not a conductor, so it will not induce / transmit overvoltage surges. Many people know this, but what is often overlooked is the lightning protection of fiber optic cables, which leads to some lightning overvoltage flashovers and damage to equipment. The main reason for this is that fiber optic cables generally have metal stiffeners and metal armors to protect the fiber optic cables. Although the fiber itself does not induce and transmit overvoltages, its metal reinforcements and metal armors are extremely easy to sense. 3. The lightning overvoltage should be properly handled, that is, the grounding protection must be done at the fiber entrance.
7. Precautions for video signal lightning protection
The concept of video signal lightning protection is relatively simple, but it often happens that the lightning protection protection fails due to the negligence of the work link, and at the same time, the video lightning protection itself is damaged. At present, most signal lightning protection products on the market generally adopt two-level protection. The first level is generally used as a rough protection, and the gas discharge tube is used as a protection device; the latter level is used for fine protection, and TVS is generally used as a protection device. In this way, the signal lightning protection device must have the points before and after, and the points between the in and out. Because the current-carrying capacity of TVS used by general signal lightning protection circuits is very limited, if the front and rear stages are connected in reverse, once an over-voltage surge comes in, the TVS is easily broken down first, resulting in damage / failure of the lightning arrester. And this happens from time to time in the market. Many business personnel of lightning protection companies are unfamiliar with this issue, and it is easy to ignore the difference between "yin in and out" and "yang in and out" when signing a contract. The procurement staff of many mine protection engineering companies also tend to ignore this problem. Just place an order to purchase a "video signal lightning arrester"; after the product arrived at the scene, the engineering staff did not consider it carefully and took it seriously, as long as it could be connected, eventually causing some video signal lightning arresters to be reversed. Shenzhen Tiantai Technology Co., Ltd. produces a video lightning arrester with dual-level protection, which can effectively prevent the above problems. Making "yin in, yang out" and "yang in, yin out" common, alleviating the working pressure of sales staff and purchasing staff, making work easier, more convenient, and more convenient for the deployment and use of video lightning arresters.
8. DC power protection, control line signal protection.
The DC power protection and control line signal protection are consistent with the common problems of video signal protection. The difference is that the DC power protection and control line signal protection are generally connected by crimping. There is no distinction between "yin" and "yang" heads. So the above-mentioned problems of selling the wrong goods and buying the wrong goods will not occur. However, site engineers must pay attention to connecting such lightning arresters properly. The commonly used identifiers are: input (IN), output (OUT), or: surge end, protection end, also known as: far end, near end. In other words, the input (IN), that is, the surge terminal, also known as the far end, should be connected to a remote line, the end that is easy to introduce lightning overvoltage; the output (OUT), that is, the protective end, also called the near end, should be connected Protect one end of the device.
The above is the whole content of how to prevent lightning strikes from security monitoring. I believe that you have already seen a certain understanding of lightning protection monitoring solutions here, and I hope to give you some help.
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