Discussion on integrated lightning protection of SPC exchange program

first, the introduction

Power Communication (Power Special Communication Network) is an indispensable part of modern power system, is one of the three pillars of modern power grid security and stable operation, and the program-controlled switchboard is an important part of Shaanxi Electric Power Communication network, the loss caused by the failure is not only economic, More seriously, it poses a potential threat to grid security. Therefore, it is very important to strengthen the security protection of SPC exchange program.
　　
The most important part of the program-controlled switchboard is integrated circuit (IC). IC anti-interference ability is low, even if from the line induction Lightning electromagnetic pulse (LEMP), can also penetrate IC components. Therefore, the program-controlled switches are prone to lightning accidents. Below I will carry on the thorough analysis and the discussion to this question.

Ii. Classification and precautionary principles of lightning disasters

Lightning can produce different forms of destruction (see figure I), the International Electrotechnical Commission has called the Lightning Disaster "the electronic era of a major public nuisance," Lightning, induced lightning, power supply, such as sharp wave of instantaneous overvoltage has become the culprit of electronic equipment damage. From a large number of communications equipment in the Lightning case analysis, experts believe that: Lightning induction and lightning wave intrusion caused by the Lightning Electromagnetic pulse (LEMP) is the main reason for the damage of communications equipment. To this end, we take the precautionary principle is "overall defense, comprehensive treatment, multiple protection." Strive to reduce its damage to the lowest point.
　　

　
　　 third, the main countermeasures of lightning protection

3. 1 Perfect grounding system
　　
Grounding is the most basic and effective measure in lightning protection system.
　　
3.1.1 According to the function of "grounding", we can divide "ground" into "work place", "Protected land" and "Thunder Ground". To the important communication equipment system, must have "the work place", it provides the standard reference potential for the entire system, has this reference potential, the system can work normally; if the system is powered by a strong power supply, the shell of the equipment must be "protected" to protect the safety of the person. If the system also has an outdoor overhead metal equipment or cable connected to it, also need the system in a reasonable position of "lightning protection" to prevent lightning high pressure string into the system.
　　
3.1.2 If the "work place", "protection" and "lightning-proof" of the communication system are installed separately, disconnected, self-contained systems, we call it "separate grounding system". If the three are merged together to form a unified grounding system, we are called "Combined grounding system". At present, Shaanxi Province dispatching communication building for the combined grounding of the grounding method. The combined grounding system eliminates the potential difference that may exist at different points of contact, and in the case of lightning strike, it can better restrain the discharge phenomenon occurring between different connecting sites.

The grounding of 3.1.3 program-controlled switchboard and the grounding of the whole building are very important. According to the standards of the Ministry of Information Industry, the grounding resistance of lightning protection grounding of telecommunication building should not be greater than 10 ohms (yd5003-94 "Special Building Design Code for Telecommunication"), the important telecommunication building grounding resistance should be below 1 ohms (ydj20-88 "Interim technical provisions for the installation design of the SPC Exchange equipment" If the grounding does not meet the requirements, when the switch is subject to strong electrical interference or lightning, may cause serious injury machine accident. Shaanxi Electric Power Company governs the use of the program-controlled switchboard Earthing method, grounding resistance <1ω (measured 0.7ω).
　　
3.1.4 in the actual wiring process, using a similar "decentralized grounding" wiring way, that is, the working ground and protection ground from the ground line, the two lines are not directly connected to the nearest, as shown in Figure II, the advantage is that when the lightning flow through the grounding network, the lightning flow only longitudinal flow, even if there is contact with bad contacts, It does not cause lateral interference.
　　
Earthing treatment of 3.1.5 switch: With a 135mm2 copper conductor, it is connected to the grounding wire line separately. Different from the system is: (1) not directly connected with the positive pole of the switch, also do not connect the cabinet with the cathode cable, line random connection. (2) Cabinet and elevated floor and base of the contact part of the insulation treatment, equivalent to the use of "suspended grounding" way to prevent similar surface layer of static electricity and building stray current into the cabinet, the communication caused interference.
　　

3.1.6 Total Wiring frame grounding: Separate from the bus row to introduce two 50mm2 copper conductor, one of which is connected to the base of the wiring frame, the other is connected to the upper end of the wiring rack on the ground copper row. The advantages of dual-line grounding are: On the one hand, it can improve the reliability of security equipment and alarm signal circuit, on the other hand, when the communication line is hit by lightning and high voltage current, the potential on the wiring frame can be reduced rapidly.
　　
The joint grounding method makes the grounding of the equipment and floor more reliable, and effectively guarantees the equipment and personal safety.
　　
3.2 Reasonable integrated wiring
　　
Program-controlled switchboard wiring is a highly professional work, its wiring scheme, in the design phase should take into account the lightning safety problem. Wiring work includes switchboard, inside, power supply line, indoor grounding wire and so on.