【 Weak current College 】 safe use of electricity and architectural lighting – section III building mine

Lightning is a natural phenomenon. Lightning is a thundercloud or between the discharge Earth thundercloud. Lightning has a devastating effect.
This section describes the common sense and Thunder and lightning. 　　Should acquire through learning, building mine classification, understand the composition of the lightning protection system, understand the structure of the lightning protection measures for lightning protection facilities maintenance requirements. First, the basics of lightning lightning damage there are two types of lightning directly stroke in a direct lightning strike on a building, called direct leiguo voltage or lightning. Another is the lightning caused by electromagnetic induction electrostatic induction or overvoltage, called induced voltage or lightning. Their characteristics are shown in the following table. Types of features direct lightning strike thundercloud directly on surface objects discharge, although lightning time is very short, only a few per to fractions of a second, but there are a lot of current adoption, up to 100 to 200kA, make a sharp rise in air temperature to Celsius 1 ~ 2 million degrees, strong shock wave, causing damage to the housing, human casualties.　　When the lightning current through a resistance or inductive objects, can produce a large voltage drop and induced voltage, damages insulation, spark, equipment damage, or even cause a fire, explosion, making harm to further expand the induced voltage or lightning over static induction is because building a thundercloud, buildings will the induction and thundercloud charge for live load on the contrary, the ground started thundercloud after discharge, in the discharge pathway in charge in and quickly, but the building at the top of the charge cannot sprang into the ground, forming a high potential, resulting in the building wire and metal equipment, metal pipe discharge, fire, explosion and personal injury Electromagnetic induction is when the lightning current through a metal body into the ground, forming a powerful magnetic field, near the metal conductor induces high potential, the conductor loop gap sparks II, civil buildings of lightning protection classification according to the building after being struck by the extent of the number of victims by lightning chance, as well as local lightning activity, that is, the importance of building and using properties, the possibility of occurrence of lightning incidents and consequences of the lightning protection requirements are divided into three categories.　　1. the first category of civilian buildings it lightning protection is of particular importance for the purpose of the State-level large buildings.　　2. the second type of lightning protection of civilian buildings it is important or personnel-intensive large buildings, as well as provincial key cultural relic protection of buildings and structures, 19 layer and above the height of residential buildings and other buildings of more than 50m. 3. the third category of lightning protection of civilian buildings ① number of lightning strikes in the calculation of buildings greater than or equal to, or exceeds 0.05 surveys confirm need lightning protection of buildings. ② the tallest buildings or in complex edge height more than buildings, 20m in lightning activity strongly area height above for 15m, lightning strike activity is relatively weak in its height above the 25m. ③ height exceeding 15m above the chimney, water towers, and other isolated building or structure, the lightning activity is relatively weak areas, and its height above for 20m. 　　④ history lightning hit areas or lightning more areas of the building. III. composition of lightning systems to as much as possible to reduce the damage caused by lightning, you need to install lightning protection equipment for buildings.　　The main building of the mine-used jieshan Qi such as lightning, lightning, lightning and the lightning, lightning through down lead, earthing device directly into the Earth. 1. jieshan jieshan qi is designed to accept a direct lightning strike of metal conductors. The main function is to receive the lightning current lead, through down lead and grounding device to the ground in relief, protection of buildings against lightning.
Jieshan protection range can be used to determine the roller ball method. Roller ball method is to hr for RADIUS of a sphere, lightning along the need to prevent the scroll position, when the ball touches only jieshan Qi (including being exploited as jieshan Qi's metal) or simply touch jieshan Qi and terrestrial (including contact with Earth and can withstand the lightning of metal), not touched on the need to protect the site, the section would be jieshan qi. Layout jieshan qi is available alone or in any combination. Protection range as shown in the figure below. ① lightning rod is the highest building of the ground, and the closest thunder clouds, because it and the Earth has a good electrical connection, it and the Earth have the same potential to enable lightning near space of electric field strength is relatively large, easily attract lightning Herald, so that the main discharge are concentrated into it, so that nearby objects than it low probability of being struck by lightning. Lightning lightning will not be able to actually cited, it makes its own mine more struck by lightning and the lightning protection from around. Due to lightning and Earth has good electrical connections, the earth energy quickly accumulated in charge delivered to thunderstorm clouds relief; or the thunderstorm clouds accumulated in charge of energy transfer to the Earth in relief, the lightning caused by overvoltage time greatly reduced, from a very large extent reduces the danger of lightning strikes. ② lightning conductor is the overhead of lightning rod is suspended at a height of grounding, and lightning rod. ③ Lightning zone is highlighted along the top of a building site of edge laying metal band as jieshan qi. ④ lightning network refers to the use of reinforced concrete structure reinforcement mesh for lightning protection.
Lightning rod is mainly used to protect outdoor transformer substation equipment, buildings and structures; lightning line is mainly used to protect the power lines; lightning, and lightning belt used to protect the building. 2. down lead down lead role is jieshan Qi and earthing devices connected together, constitute the lightning current pathway.　　In high-rise building with its columns or walls of main reinforcement as down lead, with the main structure by in-line solder-roof and jieshan connection. 3. earthing jieshan qi through down lead and Earth make good electrical connection device called grounding device.　　Grounding is grounding and grounding line. IV. building of lightning protection (1) basic lightning protection measures building mine mainly should prevent lightning, lightning and the lightning electric wave invasion of measures should be based on the actual site. ① the lightning prevention should be installed in various forms of jieshan qi. Can be installed independent of the lightning rod, in high-rise building on fitted with lightning, lightning network, etc. ② Lightning by coagulationClay roofing reinforcement down lead and earthing connection. For lightning protection request high buildings, you should use the lightning lightning network. ③ Lightning waves into the main part of the substation, the focus is on power transformers. Basic protection measures is in the high-voltage power line surge arresters for client-side installation. 　　Lightning protector should be as close as possible to install the grounding line transformer, with low voltage side of the transformer should be neutral and transformer casing joint together, and grounding connection. 2. lightning protection facilities maintenance in order to maintain a good lightning protection system to protect performance, should carry out regular checks for maintenance, in checking the maintenance of the following questions. ① jieshan Qi and arrester in any circumstances must guarantee reliable grounding. Grounding resistance should be less than 10W. ② the thunderstorm season each year, until the lightning protection system facilities, all the links for detailed inspection. If there is ground down lead serious corrosion (making the actual section decrease 30% above), should be replaced in a timely manner; have broken, loose shall immediately proceed to the welding or fastening; grounding resistance larger non-compliant should also take appropriate remedial measures (such as increase the earthing devices, etc.). ③ arrester shall in each year, thunderstorm season before conducting a test checks, performance does not meet the requirements should be replaced immediately. ④ After each time a large thunderstorm, shall promptly conduct a comprehensive inspection, see whether lightning discharges cause some connection point loose, broken or damaged, and shall immediately proceed to the appropriate repair.