We know that no matter the variable magnetic field generated by lightning in the pilot channel or the return channel of lightning, or the variable magnetic field generated after lightning enters the lightning rod system of ground structures, it will produce electromagnetic effects in a certain space. It can be the electromagnetic induction effect determined by Faraday's law of electromagnetic induction, or it can be a pulse (commonly used by LEMP) that affects all electronic equipment in a three-dimensional space, generating an induced current in a closed metal circuit, or not closing it. A high induced voltage is generated in the conductor circuit of the circuit. According to the CCIT test, the induced current on the general power line is about 3000 amperes, not more than 10KA, and the induced voltage does not exceed 6KV. In the data signal line and telephone line, the induced voltage is generally about 5KV The induced current is about several hundred amperes. In this way, it is easy to produce sparks at the gap and cause fire. When lightning strikes through the lightning rod, a strong pulsed electromagnetic field will be generated in the nearby space. When the magnetic pulse exceeds 0.07 Gauss, it will cause the computer to fail. When it exceeds 2.4 Gauss, the induced integrated circuit will be permanently damaged, especially for VLSI. With the development of science and economy, the application of computers in various industries has become very common. Many daily affairs depend on computer systems to a large extent. With a little carelessness, lightning strikes will paralyze the entire system.
① National Standard of the People's Republic of China GB50074-94 "Code for Design of Lightning Protection of Buildings"
② International Electrotechnical Commission IEC1312-1 ～ 3 "Protection of Lightning Electromagnetic Pulses"
③ National Standard of the People's Republic of China GB50174-93 "Code for Design of Computer Room"
According to the principle of overall lightning protection. Combined with modern lightning protection technology, according to the lightning electromagnetic pulse (LEMP) protection principle, for indoor electronic systems, from the three main interference sources of LEMP, various operating overvoltages (SEMP), and electrostatic discharge (ESD) in the power network, we start with Take measures on power and signal:
(1) Install a three-phase power supply lightning protection box in front of the main power distribution cabinet to attenuate the strong lightning current and high voltage introduced by the power line.
(2) At the end of the air switch in the power distribution box of the power supply line of the monitoring system room, connect the three-phase power supply lightning arrester with light alarm and lightning strike counting function to further attenuate the strong lightning current and high voltage introduced from the power line, and protect The power supply of system equipment in the entire computer room is safe.
(3) Connect a lightning protection socket in series in front of the host in the computer room to ensure the safety of the host.
(4) Connect a lightning protection socket in series in front of the display to ensure the safety of each display and each electrical device.
(5) Install power monitoring lightning arresters at the power line of the ball camera gun to effectively attenuate the lightning current and lightning voltage introduced from the power cable to protect the camera gun.
(6) Install a DC 12V power lightning arrester before each power supply of the 12V power camera gun, which can effectively attenuate the lightning current and lightning voltage introduced from the power line to protect the safety of the camera gun.
One-to-one video transmission is used between the peripheral monitoring and monitoring center. In order to better exert the overall lightning protection effect, the camera gun and the monitoring center are in a one-to-one correspondence relationship. Signal lightning arresters are installed at both ends of the host and the camera gun to protect the safety of the monitoring center and camera gun.
(1) Install information line protectors at both ends of the video cable of the camera gun to attenuate the lightning voltage and lightning current induced from the video line.
(2) Install control signal protectors at both ends of the camera gun's gimbal control line to attenuate the lightning voltage and lightning current induced on the control signal line.
In the construction of the computer room, there must be a good independent system of the computer room. Doing a good job in the construction of the equipment room grounding system can not only ensure the safety of equipment and people, but also make the equipment room equipment work stably and reliably. If the grounding system of the equipment room is not well done, it will not only cause equipment failure, burn out the components, but also seriously endanger the lives of workers.
According to different geographical environments, the grounding body has various shapes to choose from, and a grounding module should be used according to actual experience.
Grounding resistance requirement: Ra≤1Ω
It is a scientific method commonly used in grounding engineering to reduce the grounding resistance by using the Tiandun grounding module. According to the soil conditions, installing an appropriate number of grounding modules can meet the requirement of grounding resistance R≤1Ω. The use of a grounding module to reduce resistance can not only reduce the grounding resistance to the maximum, but also ensure that the grounding body remains stable for a long time, and its use period is greater than 30 years. It has the characteristics of moisture absorption and moisturizing, low ground resistance and long-term stability; after repeated large current impacts, the resistance value does not increase, nor does it become hard, brittle, or broken. Superiority; can withstand a low temperature of -40 ° C, which is also applicable in northern high and cold regions.
It is composed of non-metallic minerals and electrolytic substances with good conductivity and stability. Its birth has created a new era of grounding materials and grounding technology.The common grounding bodies are mostly metal conductors, and the most common are angle steel, round steel, steel pipes, copper rods, and copper mesh. Its characteristics are more materials, large cost, short life, poor stability, and should not be used in areas with high soil resistivity. And this kind of grounding module has less material, low cost, long life (up to 30 years), good stability, especially suitable for high resistivity soil area. If the ground point is surrounded by sand or rock formations, it can be used to form a special "human
Construction site "to solve some difficult problems in grounding work, and this product is pollution-free, non-toxic, corrosion-resistant, and very convenient to use.
The basic reason why the grounding module can obtain low grounding resistance is that in the same external dimensions, comparing metal materials doubles the contact area between the grounding body and the soil layer, thereby increasing the divergent area of the grounding body itself; The contact resistance between the grounding body and the soil is reduced; it has strong hygroscopicity and moisture retention, and fully exerts the conductive effect of the electrolytic substance in the grounding body.