If a building is fitted with a flashover but is not grounded or has a bad grounding effect, it will cause more damage to the building or its personnel when it is connected, which is even more unsafe than a building that does not have a flash picker installed.
2007 occurred in Chongqing Kaixian County Lightning Accident, is because the roof of the classroom is composed of reinforced concrete plate, in which the steel bar is not well grounded, in the Thunder when the Flash, nowhere to release, so through the classroom roof and walls of indoor personnel discharge, resulting in the classroom of seven primary school students killed dozens of people injured the tragic accident. According to the requirements of Chapter 5 ' Lightning Protection device ' in GB50057 's code for building Lightning Protection, the flashover can be made of copper, tin plated copper, aluminum, aluminum alloy, hot-dip galvanized steel, stainless steel, copper plated steel on the outer surface, etc., as long as the minimum section and thickness requirements can be met. In other words, as long as it is not so easy to rust, not due to wind and rain and easy damage, most common metal materials can be used to make flashover.
In the case of the most common iron flash lever, GB50057 requires that its minimum diameter should not be less than 8 mm. In this sense, the vast majority of building steel bars on the market, as long as their diameter is greater than 8 mm, can be used to make lightning rods, just after installation on its surface to paint one to two layers of antirust paint can be, its price is very low. In this sense, the lightning rod is not branded, because the lightning rod is just a small class in the flashover, and any metal member can be used to make the flashover.
Only emphasize the role of lightning rod, emphasize the famous brand of the lightning rod, but ignore the common flashover effect of other flashover, ignoring the flash away from the lead line and grounding device can not play a role in the objective facts, this concept is harmful and needs to be corrected. It should be noted that there are a variety of so-called well-known brands in the Market lightning rod, most of the ' pre-discharge ' or ' early discharge ' as its selling point, mostly imported from abroad so-called ' Special lightning rod ', the scope of its claim is far more than the scope of protection calculated according to the principle of the rolling ball method, its price is very expensive, often tens of thousands of yuan a root. The so-called scientific principles of these lightning rods have not been recognized in mainland China so far, and their lightning protection effect has not been recognized by practice.
Even if such a lightning rod is installed on the building, at the time of lightning protection, it is necessary to calculate according to the principle of the traditional rolling ball method, and the customers who have bought such a lightning rod at a high price should beware of the risks in this regard. Therefore, instead of spending high prices to buy such so-called special lightning rod to protect the building, it is better to follow the scientific principles of the rolling ball method, careful investigation of the scene, careful design, calculation and calibration, honest in accordance with national norms for site construction, with ordinary lightning rod, Lightning Belt and other flashover, the protection of the place to do in place,
This will achieve both safe, reliable and affordable purposes. The so-called rolling ball method, is assumed to a certain radius (according to the building protection level, 100 meters, 60 meters, 45 meters, 30 meters range) of the sphere, rolling along the outer surface of the building, when the sphere only touches the flashover and the ground, and does not touch the area to be protected, the part is protected by the flashover.
In popular terms, the place the sphere can touch is where ray can hit it, and where the sphere is out of reach is within the protection of the flashover. Calculation of the protection range of the Flashover, in the Appendix d ' Rolling ball method for determining the protection range of the flashover in GB50057 's code for the design of mine Lightning Control ', a single connecting Flash rod (lightning rod), two equal-height flash rods, two unequal high-connection flash rods, four equal-height flash rods with rectangular arrangement, and one flash line (Flash belt,
Lightning belt), two and other high-connection Flash line protection range of the protection range of the calculation method, and drawn the relevant schematic diagram. For the vast number of lightning protection industry technicians, according to the method given by GB50057, you can use a manual way to calculate some simple situation, but in the daily work, often encounter far more complex than the case listed in the scene situation, such as: a number of unequal high and not in the regular arrangement of the Flash rod, The calculation of these complex conditions can not be carried out by hand, and the GB50057 does not give a specific calculation method for the combined protection range of the connecting Flash line, the connecting Flash rod and the flash line of the unequal height. This problem is a technical problem that is often encountered in the lightning protection industry.
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