From late July to early August, it is the summer thunderstorm season. In recent years, more than 80% of the lightning disasters in internal equipment, including electrical appliances, monitoring systems, probes, etc., have been damaged. Some high-tech electronic equipments have the ability to resist interference. Very weak, love is "injured" in thunderstorm days. If there are monitoring devices such as monitoring probes and intercom systems in residential areas, there is no lightning protection device. Inductive lightning is easy to take advantage of and destroy the system. In fact, these high-tech electronic systems must have special protection, such as the installation of electromagnetic shielding devices and overvoltage protection devices that prevent lightning electromagnetic pulses and internal operating overvoltages that cause damage to electronic equipment.
Modern security monitoring products are all microelectronic products, and monitoring equipment has the characteristics of high density, high speed, low voltage and low power consumption. It is very sensitive to various electromagnetic interferences such as lightning overvoltage, power system operating overvoltage, electrostatic discharge, electromagnetic radiation, etc., which makes the monitoring system equipment vulnerable to lightning/overvoltage damage, and the consequences may cause the entire monitoring system to operate. Failure and cause unpredictable economic losses and security risks. Monitoring the entire system is widely distributed, the line is long, and it is easy to be damaged by the inductive lightning attack. Therefore, the equipment at both ends of the transmission line, including the camera part, the optical part of the extension room, and the remote access of the local area network are the key parts of lightning protection, each part Functional devices must take measures such as power supply lightning protection, signal lightning protection, and grounding for safety. Frequently asked questions about installing lightning protection equipment in the monitoring system?
1. The grounding resistance is too large or there is no grounding. The "Digital Security Monitoring System Engineering Design Specification" and "Building Information System Lightning Protection Technical Specifications" do not clearly specify the grounding resistance of the lightning protection system. Generally, the grounding resistance of the design monitoring system is determined according to the resistance of the computer room and the grounding resistance of the information system: the independent grounding is not more than 4 ohms, and the combined grounding resistance is not more than 1 ohm. Specifically, more different geological conditions can appropriately increase the grounding resistance of the monitoring system. For example: forest fire prevention unit, camera requirements must be installed on the ridge, the address is bluestone, there is no river ditch within 200 meters, no excavation is possible. Large gravel and soil. At this time, if the grounding of the monitoring system in this particular place is required to be no more than 4 ohms, the cost is ten times or even several times that of the monitoring system itself, then choose the appropriate grounding resistance, and use the cable of the large-pass flow as the connection. Ground wire.
Second, there is no direct lightning protection measures, this kind of situation is more common is the gun camera, some people think that the three-in-one signal lightning arrester has been installed, the grounding [industrial electrical network -cnelc] is also done, there should be no problem, but However, it is not known that the arrester is a tool for lightning protection and lightning, and it has no effect on direct lightning. There are several ways for lightning to damage electronic information systems: 1. Mechanical effects, such as lightning strikes on trees, sometimes breaking the poles of large trees, mainly relying on the mechanical effects of lightning strikes. 2, the thermal effect, the instantaneous temperature of the lightning strike point can reach more than 3000 degrees, so that the metal is instantaneous. 3, electromagnetic effect, this is an invisible killer, it works through electromagnetic induction to generate instantaneous high current burning equipment. Direct lightning protection is only required to rely on the lightning rod device, which changes the running direction of the lightning, making lightning less likely to hit directly. There is also a case where the lightning rod is actually installed using the curved ball machine. In this case, the metal rod itself has already protected the ball machine, and it is not necessary to increase the cost and install the lightning rod.
3. The signal lightning arrester is too far away from the equipment to be protected. If the lightning arrester is installed too far away from the equipment, there is no way to eliminate the lightning current induced on the communication line and power line from the lightning arrester to the front end of the equipment. Therefore, it is recommended that the signal lightning arrester should be installed directly to the front end of the monitoring equipment, especially where the signal power supply line is clearly visible.
Fourth, the problem of the grounding cable, in order to save costs, often use the metal rod as the down conductor of the working grounding system, regardless of "right" and "no". According to the design, the metal rod is used as the direct lightning protection system to lead the lower line. At this time, the working ground is connected to the metal rod. If there is a direct lightning strike, there is no voltage difference between the front end of the signal lightning arrester and the metal rod body, that is to say, your Direct lightning strikes directly impact the signal lightning arrester or the power supply arrester, which will cause the arrester to age prematurely or be damaged on the spot. Therefore, it is recommended that the work line should be taken out separately.
The choice of five or three-in-one surge protector (or BNC surge protector), according to the specific conditions of the market, and time installation experience, BNC signal electrophoresis protector is set in the lightning protection range for a long time, this The protection of the matter is not enough. For it, there are surges, spikes, burrs, etc., causing surges, spikes, and burrs to be activated by nearby large-scale power tools. Shutdown, as well as changes in nearby electromagnetic fields, etc., require not only the protection of the pressure sensitive or discharge tube, but also a logic filter circuit to provide a safer power environment. The latter factor has been ignored. Lightning protection is a more complicated problem. The lightning protection design of the safety monitoring system depends not only on the performance of the lightning protection device, but more importantly, the geography of the monitoring system should be considered before the design and construction of the monitoring system. Environment, design appropriate cable deployment, shielding and grounding methods. In short, lightning protection design should be considered in order to achieve good results.
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