Users of process-controlled switches should be aware that program-controlled switches are prone to lightning strikes. Therefore, lightning protection measures should be implemented before use. Program-controlled switches are prone to lightning accidents because the main components of integrated circuit ICs have very low anti-interference ability, and often ordinary lightning electromagnetic pulses are very likely to damage ICs, so ICs are very fragile and need to be well-made. Precautions.

Classification and Prevention of Lightning Disasters

Lightning strikes can produce different forms of damage. The International Electrotechnical Commission has called the lightning disaster a “great public hazard in the electronic age”. Lightning strikes, induced lightning strikes, and power spikes have become the culprit in the destruction of electronic devices. From the analysis of a large number of communications equipment lightning strikes, experts believe that lightning electromagnetic pulses (LEMP) caused by lightning and lightning wave intrusion are the main causes of damage to communication equipment. The precautionary principle we have adopted for this purpose is "total defense, comprehensive governance, and multiple protections." Strive to reduce the harm it produces to the lowest point.

Major countermeasures for lightning protection

Grounding is the most basic and most effective measure in the lightning protection system. According to the different role of "grounding", we can divide "ground" into "workplace", "protection ground" and "lightning protection ground". For important communication equipment systems, there must be a "workplace", which provides a standard reference potential for the entire system. With this reference potential, the system can work properly; if the system is powered by a strong power supply, the equipment housing must also be Connect the “protection ground” to protect personal safety; if the system still has outdoor overhead metal devices or cables connected to it, the system must also be “grounded” at a reasonable location to prevent lightning strikes from entering the system in high voltage.

If the "work place", "protection place" and "lightning protection place" of the communication system are installed separately, they are not connected to each other, and they are self-contained systems. We call this the "distribution grounding system." If the three are merged and set together to form a unified grounding system, the grounding of the PBX controlled switch that we will call the "integrated grounding system" uses the joint grounding method, and the grounding resistance of the grounding body is <1 Ω (0.7 Ω measured).

In the actual wiring process, similar to the "distributed grounding" of the wiring, that is, the working ground and the protective ground line are drawn from the ground line, the two ground lines are not directly connected nearby, as shown in Figure 2, the advantage is When the lightning current flows through the grounding grid, the lightning current flows only vertically, and even if there is a poorly contacted junction, it will not cause lateral interference. Grounding of the switch: Use a 135mm2 stranded copper conductor that is individually connected to the ground wire bank. Different from the system, it is: (1) It is not directly connected to the positive side of the switch, nor is it connected randomly to cables or wires with positive wires. (2) The contact parts of the cabinet and the raised floor and the base are all insulated. This is equivalent to a "floating earth" method to prevent the static electricity of the adjacent surface and the stray current of the building from entering the cabinet and causing interference to the communication. .