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What issues should I pay attention to in lightning protection?
Lightning protection is a very complicated problem. It is impossible to completely eliminate the effects of lightning overvoltage and induced overvoltage by relying on one or two advanced lightning protection equipment and lightning protection measures. The factors that cause lightning strikes are eliminated, and comprehensive prevention and control—lighting, equalizing, shielding, grounding, and shunting (protection) can be used to minimize the damage.
1. The lightning flashing device is the lightning rod, lightning protection belt, lightning protection line or lightning protection net that we often say. The lightning is the lightning discharge that can be selected within a certain range. The discharge channel cannot be arbitrarily selected, but only according to people's prior design. The prescribed channel of the lightning protection system discharges lightning energy into the earth.
2. When the lightning-collecting device is connected to the lightning device, the down-conductor line immediately generates a high potential, which will cause a side flashover of the conductor that is still at the ground potential around the lightning protection system, and increase its potential, thereby And equipment constitutes a hazard. In order to reduce this flashover hazard, the simplest method is to use a voltage equalizing ring to connect the equipotentials of the conductor at ground potential until the grounding device. Indoor metal facilities, electrical installations and electronic equipment, if they are not in compliance with the specified safety requirements with the conductors of the lightning protection system, especially the lightning receptors, they should be connected to the lightning protection system with thicker conductors. Equipotential bonding. In this way, when the lightning current passes, all the facilities in the room immediately form an "equal potential island" to ensure that no harmful potential difference is generated between the conductive parts, and no side flashover discharge occurs. The perfect equipotential bonding also prevents counterattacks caused by rising ground potential caused by lightning currents entering the ground. In order to completely eliminate the destructive potential difference caused by lightning, it is particularly necessary to implement equipotential bonding. Power lines, signal lines, metal pipes, etc. must be equipotentially connected through an overvoltage protector, and the interfaces of the inner protective areas are also the same. The local equipotential bonding is carried out in accordance with this and finally connected to the equipotential bonding busbar.
3. Shielding is to shield the objects to be protected by conductors such as metal mesh, foil, shell or pipe, so that the channels of lightning electromagnetic pulse wave intrusion are all cut off. All shields, shells, etc. need to be grounded. Shielding is the most effective way to prevent the impact of lightning electromagnetic pulse radiation on electronic equipment.
4. Grounding grounding is to let the lightning current that has been built into the lightning protection system flow smoothly into the earth, but not to let the lightning energy concentrate on somewhere in the lightning protection system to cause damage to the protected object. Good grounding can effectively discharge the lightning. Energy, reduce the voltage on the down line to avoid counterattacks. In the past, some specifications required electronic equipment to be grounded separately in order to prevent stray currents or transient currents in the power grid from interfering with the normal operation of the equipment. Before the 1990s, the communication and navigation equipment was mainly based on electronic tube devices, and the analog communication method was adopted. The analog communication was particularly sensitive to interference. In order to resist interference, the method of separating the power supply from the communication ground was adopted. Now, lightning protection engineering does not advocate separate grounding. Separate grounding is not recommended in the iec standard and itu related standards. The US standard ieeestd1100-1992 sharply points out that it is not recommended to use any so-called separate, independent, computer, electronic or other such incorrect earth. The grounding body acts as a connection point for the grounding conductor of the device. Lightning protection grounding is the most basic part of lightning protection system, and it is also the most basic safety requirement in lightning protection installation acceptance specification. The grounding is not good, and the lightning protection effect of all lightning protection measures cannot be exerted.
5. Diversion (Protection) This is the focus of the rapid development of modern lightning protection technology and is a key measure to protect various electronic equipment or electrical systems. The so-called shunt is to connect an appropriate lightning arrester spd in parallel with any lightning-proof grounding device or grounding wire from any outdoor conductor (including signal lines such as power supply lines, data lines or antenna feeders), when lightning strikes or lightning strikes effect online. When the overvoltage wave generated on the road enters the room or equipment along these wires, the resistance of the arrester suddenly drops to a low value, which is close to the short circuit state, and the lightning current flows into the ground from here. After the lightning current is shunted, there will still be a small amount of wire entering the device along the wire. This is very dangerous for some microelectronic devices that are not resistant to high voltage. Therefore, for such devices, multiple stages should be performed before the wires enter the casing. Diversion (ie no less than three levels of lightning protection). The research and development of arresters is now beyond the scope of diversion. Some arresters can be connected directly to the signal line or the feeder of the antenna. They allow the useful signal to pass smoothly and block the lightning overvoltage wave. When shunting is used as a lightning protection measure, special attention should be paid to the choice of the performance parameters of the arrester, since the installation of additional facilities will affect the performance of the system more or less. For example, the access of the signal lightning arrester should not affect the transmission rate of the system; the loss of the antenna feeder lightning arrester in the passband should be as small as possible; if used on the orientation device, the positioning error cannot be caused.
6. When avoiding the site selection of buildings, you should avoid the multi-mine area or the location that is vulnerable to lightning strikes, so as to avoid increasing the expenses and expenses of lightning protection projects in the future.