Weak current system lightning protection
Multi-level classification (class) protection principle
According to the different functions of electrical and microelectronic equipment and different protected programs and their protective layers, the protection points are classified and protected; according to the electrical path that lightning damage may invade, the system can be multi-level from power line to data communication line. Multi-level protection.
External passive protection
In the 0-level protection zone, the external protection is passive, mainly including lightning rods (net, wire, belt) and grounding devices (grounding wire, grounding pole). Protection principle: When the thundercloud discharge is close to the ground, it causes the ground electric field to be distorted. At the top of the lightning rod (wire), the inter-exchange electric field strength distortion is formed to affect the development direction of the lightning pilot discharge, and the lightning is guided to discharge the lightning rod (wire), and then the grounding lead-down line is used, and the grounding device introduces the lightning current into the earth, thereby Protect objects from lightning strikes.
The power supply is partially protected, and the lightning infringement is mainly invaded through the power supply line. The "power surge protector" is connected to the power line to contain transient overvoltages and bleed surge currents. From the total incoming line to the end of the powered device, three levels of protection are usually configured. After step-by-step voltage limiting and discharging, the lightning energy is gradually eliminated to ensure the safety of the electrical equipment. The overvoltage protection shall be divided into three parts according to the national standard: it is recommended to add a lightning arrester at both ends of the cable inner core between the back end of the high voltage transformer and the main switchboard of the building as the first level protection; in the main distribution board to the floor distribution box A lightning arrester is installed at both ends of the cable core wire as a second-level protection; a lightning arrester is installed at all important and sophisticated equipment and the front end of the UPS as a third-level protection.
Signal part protection, for various types of signal systems, should be divided into rough protection and fine protection. The coarse protection level is determined according to the level of the protected area, and the fine protection is determined according to the sensitivity of the electronic device. After the "signal lightning arrester" is connected to the signal line, on the one hand, it is necessary to cut off the passage of lightning into the equipment, and at the same time, it must be able to discharge to the ground quickly. On the other hand, it must ensure that the signal passing through the lightning protection device is not under normal conditions. Damage, so that the equipment can work properly.
Handling by land
In the construction of computer rooms and various types of weak motor rooms, a good grounding system is required. Because all lightning protection equipment needs to discharge lightning current into the earth through the grounding system, thus protecting equipment and personal safety. If the grounding system of the equipment room is not well done, it will not only cause equipment failure, but also burn out the components, which will seriously endanger the safety of the workers. In addition, anti-interference shielding problems and anti-static problems need to be solved by establishing a good grounding system.
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