Weak electrical equipment lightning protection technical measures - News - Global IC Trade Starts Here Free Products

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

TP-IP4220CZ6 5V 0.35PF breakdown voltage 6V SOT

Shunuo varistor / ESD varistor / product complete / Sunlord first-class agent

SMD aluminum electrolytic capacitor

Crystal oscillator

With the rapid development of modern technology, the application of electronic information equipment has penetrated into various fields, and various electronic and microelectronic equipments have been widely used in various industries. Due to the low overvoltage resistance of these systems and equipment, the electromagnetic effects and thermal effects generated by lightning high voltage and lightning electromagnetic inrush currents may cause interference or permanent damage to the system and equipment, resulting in large economic losses. Therefore, it is very important to solve the problem of protection against lightning disasters in electronic information systems. The diversification and complication of electronic information system equipment, the low working voltage of microelectronic components, and the relatively small amplitude of communication signals, such as the installation of lightning protection facilities in the loop, will inevitably affect the reliability of communications, networks and other equipment. Safe and unobstructed. This brings certain difficulties to the overvoltage protection of weak current equipment. In order to reduce lightning damage and cause damage to weak electrical equipment such as automatic control systems, causing direct and indirect major economic losses, it is necessary to study the lightning protection and grounding technologies of weak electrical equipment and take effective lightning protection measures.

1 The main cause of damage to weak electrical equipment

1.1 Direct lightning The so-called direct lightning refers to the lightning strike point directly acting on the equipment or acting on the transmission line, causing damage to the equipment caused by the transmission line. The degree of equipment damage caused by direct lightning strikes is generally serious. Generally, lightning rods are installed and lightning protection belts are installed for lightning protection.

1.2 Inductive thunder The so-called inductive thunder means that the lightning strike point occurs hundreds of meters or several kilometers away from the device. The magnetic field around the lightning strike point changes strongly, and a certain lightning voltage amplitude is induced on the nearby equipment or metal conductor. Damage to the weak current device caused by overvoltage. In fact, most of the damage caused by lightning strikes (99%) is caused by inductive lightning. Therefore, we must pay attention to the prevention of inductive lightning.

1.3 Characteristics of Inductive Thunder Voltage 1 Lightning wave is shock voltage, short acting time, generally only a few microseconds to tens of microseconds of non-periodic changing voltage, can be considered as transient voltage change: 2 magnetic field around lightning strike point occurs When there is a strong change. A certain lightning voltage amplitude will be induced on nearby equipment and metal conductors; 3 the lightning induced voltage intensity generated on the equipment, device or conductor and its conductor length, section, installation height and magnetic field strength (lightning strike strength) In proportion, it is inversely proportional to the distance to the location where the lightning strike occurs. The weak current equipment is mainly composed of electronic components, transistors, integrated circuits, etc., and its working voltage is low (generally 5V to 12V), and the anti-lightning interference capability is poor. Even a small lightning induced voltage may cause damage to weak electrical equipment.

2 Lightning protection measures for weak electrical equipment

According to the IEC61312 standard, weak current equipment should be equipped with multi-level lightning protection measures. Overvoltage protection for 380V low voltage lines. According to the national standard, there should be three parts: a lightning arrester or a protector is applied to both ends of the cable core wire at the back end of the high voltage transformer to the total power distribution of the secondary low voltage equipment for primary protection. A lightning arrester or protector is installed on both ends of the inner core of the cable between the total switchboard of the secondary low-voltage equipment and the Distribution Box of the secondary low-voltage equipment for secondary protection. Install lightning arresters or protectors on all important, precision equipment and front ends of the UPS as a three-level protection. Since the lightning current is mainly composed of the first lightning current and the subsequent lightning current, the protection of the lightning overvoltage must also consider how to suppress (or shunt) the first lightning current and the subsequent lightning current. While taking multiple levels of protection, energy coordination and decoupling measures must also be considered. There are two measures for lightning protection of weak current systems: external lightning protection and internal lightning protection. External lightning protection can directly introduce most of the lightning current into the underground leakage; internal lightning protection can block lightning waves introduced along the power supply or signal line. These two lines of defense work together and do their part.

2.1 External protection measures External protection refers to the safety protection of the building body where weak electrical equipment is installed. It can be used such as lightning rod, shunt, shielding net, equalization potential and grounding. This kind of protection measures are more important and relatively perfect. At present, the external protection measures for weak current equipment mainly include: 1 Using the lightning rod of the building to introduce the main lightning current into the earth. 2 When the lightning current is introduced into the earth, the lightning current is shunted to avoid causing overvoltage damage to the equipment. 3 The use of metal parts and steel bars in the building can be used as an irregular Faraday cage to provide a certain shielding function. If the equipment in the building is a low-voltage electronic logic system, remote control and other low-power signal circuits, it needs to be installed. Special shielding net. 4 The potential of each point of the building is balanced to avoid damage to the equipment due to the potential difference. 5 Ensure that the building has a good grounding-2 to avoid damage to the equipment when the ground potential is raised during lightning strikes.
2.2 Internal protection measures Internal lightning protection refers to the protection of over-voltage (lightning or over-voltage inside the power supply system) of weak electrical equipment inside the building. When the equipment is subjected to over-voltage attack, the protection device can quickly discharge energy and protect the equipment. Protected from damage, equipotential bonding, shielding, protection isolation, proper wiring, and overvoltage protectors can be used. Internal lightning protection is divided into power lightning protection and signal lightning protection.

2.2.1 Power supply lightning protection system is mainly to prevent lightning waves from causing damage to computers and related equipment through power lines. In order to avoid the high voltage after the residual voltage after the lightning arrester is discharged to the ground or because of the greater lightning current, the subsequent equipment will continue to be destroyed after destroying the lightning arrester, and the cable will be prevented from being subjected to secondary induction. The principle of hierarchical protection and gradual discharge shall be adopted. First, install a primary power supply lightning arrester with a large discharge current at the main entrance of the building power supply; first, install a secondary or tertiary power supply lightning arrester at the entrance of important floors or important equipment power supplies. In order to ensure lightning strike, the high voltage first passes through the primary power supply lightning arrester, and then passes through the secondary power supply lightning protection device. The distance between the primary power supply lightning protection device and the secondary power supply lightning protection device is greater than l0-15m. If the distance between the two is not enough, a lightning protection box with a coil can be used, so that the secondary power lightning protection device can be prevented from being damaged by lightning strike first.

2.2.2 Signal lightning protection system Because lightning waves can induce high instantaneous impact energy on the line, network communication equipment is required to withstand the transient impact of higher energy. At present, most of the equipment is highly integrated due to electronic components. In order to reduce the overvoltage and overcurrent resistance level, necessary lightning protection devices must be installed at the network communication interface to ensure the safe operation of the network communication system. It is very important to select the appropriate protection device for lightning protection of the communication system. The lightning protection product should be fully matched with the communication system. For information systems, it 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. Due to insufficient attention to the lightning surge protection of weak electrical equipment, lightning surges damage the equipment. Therefore, while improving the external protection of weak electrical equipment, it is necessary to strengthen the internal protection of weak electrical equipment. 1 Improve the external lightning protection of weak currents, and introduce most of the lightning current directly into the underground. 2 Block the overvoltage wave introduced along the power line or data and signal lines. 3 Limit the range of surge overvoltage overcurrent on the clamped device to be protected on the device. 4 The high-absorption energy shunt device (arc arrester) diverts the lightning over-voltage (pulse) energy to the earth. The quality and performance of the protector used in the shunting (limiting) technology is the key to network protection. Therefore, it is important to choose a qualified lightning arrester or protector. 5 uses short-term technology. The connection between the devices is as short as possible to reduce the magnitude of the lightning induced voltage on the wires. 6 is shielded. The use of a shielded cable will reduce the lightning induced voltage strength, but the shield should be reliably grounded. 7Isolation and insulation are used to weaken the lightning induced voltage. The fixing bracket of the antenna is insulated from the lightning rod by the insulating rod, and the battery pole bracket is separated from the lightning rod body floor by an insulator. 8 manual isolation. If weak electrical equipment is required, manually connect the power switch and plug in the network line. Otherwise, disconnect the above line. 9 voltage suppression technology. For unattended equipment and equipment that requires continuous communication with the outside world, the lightning induced voltage must be limited to the voltage that the equipment is subjected to to prevent damage to the equipment. In order to achieve the ideal lightning protection effect, the lightning protection device must be installed according to the working principle, working conditions, power level and impedance level of the equipment. A good grounding system is required, because all lightning protection systems need to ground the lightning current to the earth to protect equipment and personal safety. If the grounding system of the equipment room is not well done, it will not only cause equipment failure, burn out components, but even endanger the safety of workers. In addition, anti-interference shielding problems and anti-static problems need to be solved by establishing a good grounding system.

3 Conclusion

Misunderstanding of Lightning Protection Equipment for Lightning Equipment At present, the lightning protection countries of weak current equipment have not yet issued relevant technical standards. Many designs still apply lightning protection grounding specifications for strong electricity. In fact, the weak current equipment is generally inductive lightning, and the grounding current is relatively small. Recognizing this point is of great significance for the selection of lightning protection schemes for weak electricity products and the limitation of engineering cost.