First of all, lightning short-circuit almost can be used in the building foundation of the rebar as a short-circuit body, but the rebar must be unfolded electrical all-through welded together, and the use of vertical rebar in the house columns to do the lead wire, has been connected to the roof lightning facilities.
Secondly, many refused to lead the rebar more than one out is used to do artificial short circuit, that is used in the building foundation itself to do short circuit can not exceed the specified resistance refused to be used, and even if this is done artificially short-circuited, the effect is to use the foundation of the building itself to do a short circuit body is much worse than. So it is necessary to use the building foundation rebar to do short circuit body.
Note: 1. The foundation rebar will unfold a better electrical all through, at least to ensure that the periphery of a circle is all through, spanning the material recommended for the 12MM round steel, weld length of about 150MM. 2. The average lead spacing should be greater than 25 meters, if the house is not large, the four corners have a lead line is good.
3. Each lead wire is recommended to be used for two 16MM bars or four 14MM bars. Be sure to make sure that the lead wire connects the short circuit body and the roof lightning protection device into one.
2. How to debug the lightning protection grounding
Grounding network, busbar, and grounding electrode should be debugged? A: The grounding device debugging is mainly on the grounding device grounding resistance value test to determine whether the grounding device to meet the engineering design requirements.
(1) quantity calculation independent grounding device debugging to "group" as a unit of measurement, grounding network to "system" as a unit of measurement, the amount of work according to the construction drawings show the number of calculations. (2) quota application of grounding device commissioning, the quota is divided into independent grounding device commissioning and grounding network commissioning, the use of the corresponding quota subheadings.
(3) debugging should pay attention to the following issues: 1) independent grounding device according to the "group" calculation, such as a column transformer has an independent grounding device, if the test - that is, according to a group of calculations. 2) Determination of lightning rod grounding resistance, each lightning rod has a separate grounding network (including independent lightning rods). (including independent lightning rod, chimney lightning rod, etc.), are calculated as a group.
3) Determination of grounding resistance of the grounding network, power plant or substation connected to a mother network, according to a system; since the mother network is not connected to the mother network of the plant's independent grounding network, another system, such as a separate substation in the plant grounding network is not connected to the mother network of the plant, it should be calculated according to a system. Large building complexes have their own grounding network (grounding resistance value design requirements), although the last will be connected to the grounding network, but should be calculated according to a system.
4) Grounding device commissioning quota applies to all electrical equipment installation project grounding device commissioning.
3. Why lightning rods can avoid lightning
Thunder and lightning is a common weather phenomenon in summer.
The dazzling lightning, rumbling thunder, both make people feel frightened, but also make people curious about them. Through modern scientific research, people have revealed the secrets of lightning.
It turns out that lightning is a spark discharge phenomenon that occurs in the clouds between clouds and clouds, between clouds and air. Lightning and thunder are always produced at the same time, collectively known as lightning.
Lightning is closely related to our lives. Lightning can make the air in the nitrogen, oxygen and other gases in a series of chemical reactions, the formation of new substances and rain mix, and land on the ground and the soil inorganic substances synthesized new, can be absorbed by the plant nitrogen fertilizer.
It has been determined that the annual thunderstorms on Earth can synthesize about 400 million tons of nitrogen fertilizer. Lightning is not only conducive to biological growth, but also has the effect of purifying the air.
Lightning can also eliminate viruses and germs in the air, and reduce the occurrence of pests and diseases in crops. But lightning can also bring disasters, for example, in dry weather, lightning can cause forest fires, sometimes also attack the human body, and sometimes destroy buildings ...... For a long time, people are always looking for ways to inhibit lightning to reduce disasters.
In the 18th century, the American scientist Franklin invented the lightning rod. It is a tall building on the erection of a sharp copper rod, and then connected to a metal wire, the other end of the line buried in the ground.
In this way, the negative charge in the clouds will follow this device into the ground, you can avoid the harm caused by lightning.
4. What to know about lightning protection
Generally speaking, lightning strikes are likely to occur in places where the soil resistivity is small and the soil resistivity changes significantly.
Areas with metal deposits, riverbeds, groundwater outlets, hillsides bordering rice paddies, mountain slopes and foothills, riversides, lakesides, seashores, low-lying areas, and places with high water tables are all vulnerable to lightning strikes. Some isolated towers, chimneys and other tall buildings (structures) are also vulnerable to lightning strikes.
When a thunderstorm comes, trees are vulnerable to lightning strikes because they are taller. You should stay away from large trees and crouch down as far as possible with your feet together during a thunderstorm.
Why the bathroom into a high incidence of lightning strikes in the home, the bathroom plumbing more metal body, conductivity, so the thunderstorm days bathroom naturally become a high incidence of lightning strikes in the home. And, the public installed on the roof of the solar water heater is not connected to the vast majority of lightning equipment.
Some solar water heaters, installed in order to get good light, and even built a high iron frame, in case of thunder, the water heater may become a "lightning", resulting in lightning strikes. How to prevent electrocution accidents bad weather to prevent electrocution should pay attention to the following points: 1.
Gale force winds, thunderstorms and other inclement weather, should minimize the out. If you must go out to walk, you should carefully observe the terrain and walk cautiously to avoid stepping on power lines.
You should avoid walking near power facilities such as utility poles and pylons, and you should also walk around hanging power lines. 2.
Do not go barefoot when walking outside. 3.
Indoors, in case of thunderstorms and windy weather, household appliances in operation should be turned off and unplugged in time; do not go barehanded and barefoot to repair electrically charged wiring or equipment in your home; if your home is flooded inadvertently, you should cut off the power supply immediately, in order to prevent accidents from occurring due to water ingress and insulation damage to household appliances in use. 4.
When walking outside on a rainy day, pay attention to observation, do not contact with street lamp poles, signal light poles and metal parts of the floor billboards, and should go around the place where there is water. 5.
When you find power distribution panels, van-type substations and other power facilities flooded, you should notify the power supply department in time to deal with the problem while you and other people are not close to them. How to give first aid after being struck by lightning After being struck by lightning, you can take the following ways to give first aid:
The injured person lies down on the ground, loosening the buttons of the clothes, belt, etc.. 2.
Immediately mouth-to-mouth breathing and extrathoracic cardiac compression, insist until the patient woke up. 3.
Hand-guided or needled Renzhong, Shixuan, Yongquan, and Vital Gate points. 4.
Send to the hospital for first aid. Don't take shelter under trees during thunderstorms.
Don't go into the shed during a thunderstorm. Don't overload the power line.
Don't use wet hands and wet cloth to wipe the head of the electrified lamp. Thunderstorm season air humidity, it is the season of electrocution accidents, the public should be replaced in a timely manner old aging or damaged wires, to prevent hanging down, leakage and other accidents, injuries and personal safety.
On the public's concern about the defense against lightning, to prevent accidental electrocution, safe use of electricity, electrocution first aid and other knowledge, the relevant experts have answered. How to prevent lightning strikes during thunderstorms Some people believe that the building as long as the installation of lightning rods and lightning straps, the building people and equipment will not be struck by lightning.
This view is wrong. First of all, lightning rods have a certain protection range, when the building beyond the protection range of lightning rods, will not be protected by lightning rods.
Secondly, the performance of the lightning rod is in line with technical requirements, such as material specifications, grounding resistance, etc., if the role of the loss due to disrepair, not only can not play the effect of lightning, but also increase the probability of lightning strikes. Furthermore, lightning rods can only protect the building from lightning strikes, but not to protect the people inside the building and equipment from lightning strikes.
Lightning rod can only be 50% of the lightning energy released into the ground, the remaining 50% of the energy will be through the induction effect and energy coupling, through a variety of pipelines and equipment released into the ground. Do not use radios and televisions with external antennas and do not answer the phone.
2. If you are in the field, you should immediately look for a shelter, such as a lightning rod-equipped, steel-framed, or steel-paneled concrete building as a lightning shelter, or a vehicle with a full metal compartment.
3. When there is no shelter, do not approach the open area or the lonely tree on the top of the hill, which is most vulnerable to lightning strikes.
Don't stay in open water and small boats; try to avoid the edges of tall trees, around power lines, flagpoles and near tall objects without lightning protection such as haystacks and tents, and don't stay close to railroad tracks, long metal railings, and other bulky metal objects, and not on hilltops, heights, and other places. 4.
During lightning, it is best not to ride horses, bicycles and motorcycles; not to carry metal objects in the open air; and not to go near any part of lightning protection equipment. 5.
If you can not find a suitable place to avoid lightning, should be used to minimize the center of gravity and reduce the contact area between the human body and the ground, you can crouch down, feet together, hands on the knees, the body forward bending, and never lie on the ground, trenches or pits of earth, such as can be draped in raincoats, the effect of lightning protection is better. In the field of the crowd, whether in motion or static, should be pulled away from the distance of a few meters, do not crowded together, can also hide in the larger caves.
6. Note that when your hair stands on end or your skin trembles, a lightning strike may occur and you should immediately fall to the ground.
People who are struck by lightning may be burned or go into severe shock, but are not electrically charged and can be safely rescued. 7.
Be sure not to use your cell phone when there is strong thunder and lightning! What are the essentials of personal protection against lightning Personal protection against lightning should pay attention to the following points:1. should stay indoors and close doors and windows; people who work outdoors should take shelter inside buildings.
2. It is not advisable to use electrical appliances such as TVs and stereos that have no or insufficient lightning protection, and it is not advisable to use water taps.
3. Do not touch the antenna, water pipes, barbed wire, metal doors and windows, building facades, and stay away from electrically charged equipment such as power lines or other similar metal devices.
4. Reduce the use of telephones and portable phones.
5. Do not swim or engage in other water sports, outdoor ball games should not be played, leave the water and other open spaces, and seek shelter.
6. Do not stand on the top of a hill, on the roof of a building, or anywhere else close to an object with high conductivity.
7. Do not handle flammable materials in open containers.
8. Stay away from trees and masts in the wilderness when you cannot take shelter in a building with lightning protection.
9. It is not advisable to carry umbrellas, badminton rackets, golf clubs, etc. on your shoulders in an open field.
10. It is not advisable to drive a motorcycle or ride a bicycle.
How to prevent electrocution Measures to prevent electrical fire accidents.
5. What is the grounding device
The role of lightning protection To prevent lightning hazards, it is necessary to strict lightning protection devices.
A complete lightning protection device consists of three parts: flashover (lightning rod), lead wire and grounding body. Flashover is a metal conductor that receives lightning strikes directly, which is installed on the top of the protected object or on an independent lightning arrester.
In the initial development stage of the lightning channel, because the thundercloud is relatively high from the ground, so the direction of the channel development is not affected by the ground objects, but when the lightning channel development to a certain height, the protruding objects on the ground will affect the direction of the development of the channel. Therefore, flammable and explosive chemical storage areas, such as warehouses, tanks, etc., must be equipped with a lightning rod (lightning rod), the channel will develop in the direction of the lightning rod, this is because the lightning rod is higher than the flammable and explosive chemical storage protruding objects and have a good grounding.
So, the essential role of the lightning catcher is to draw lightning to itself, and safely introduce the lightning current to the earth. The role of the grounding device lead is connected to the flashover and grounding device of the metal conductor, its role is to pass the lightning current on the flashover to the grounding body, the lead is generally made of round steel or flat steel, such as corrosive places should be appropriately increased cross-sectional area, the lead is generally laid along the outside wall of the building, the laying of the route should be as short as possible, but straight, should be fixed firmly, the fixed fulcrum should not be greater than 1.
5. To 2 meters. In the ground connection with the application of steel pipe through the pipe, in order to prevent external mechanical damage to the lead line and corrosion prevention.
In order to check the convenience of measurement, 1.5-1.
8 meters from the ground shall be set to break the connection card. Grounding body including grounding devices and devices around the soil or concrete, its role is to effectively drain the lightning current into the earth, now commonly used grounding devices are horizontal grounding electrode, vertical grounding electrode, extension of the grounding electrode and the foundation grounding electrode.
The grounding of flammable and explosive chemicals is generally used vertical grounding electrode, that is, with a 2. 5 meters above the angle, round steel, steel pipe or copper column profiles made of vertical into the soil, when the grounding can not meet the requirements, can be used to ring grounding electrode group and radiating grounding electrode group, in order to prevent corrosion, can be coated with anticorrosion agent before burying.
Some areas of high soil resistance, general grounding methods can not meet the grounding design requirements, artificial methods can be used to reduce the resistivity of the grounding soil, that is, with the soil replacement method or chemical treatment method. What are the grounding requirements for lightning protection grounding? Lightning grounding: In order to quickly lead the lightning current into the earth, in order to prevent lightning damage for the purpose of grounding is called lightning grounding.
The building belongs to the first class load, should be designed according to the first level of lightning protection building protection measures, the flasher using a combination of needle belt flasher, lightning belt using 25 * 4 (mm) galvanized flat steel in the roof of the composition of the ≤ 10 * 10 (m) of the grid, the grid and the roof metal components for electrical connections, and the building column head reinforcement for electrical connections, the lead wire using the column head in the steel, ring beam reinforcement, the floor Reinforcement and lightning protection system connection, all metal components of the external wall should also be connected to the lightning protection system, column head reinforcement and grounding body connection, composed of multi-layer shielding cage lightning protection system. This can not only effectively prevent lightning damage to the building equipment, but also prevent external electromagnetic interference.
Various types of lightning protection grounding device frequency grounding resistance, generally should be determined according to the counterattack conditions of falling thunder. Lightning protection devices, such as working with electrical equipment grounded in a total grounding network, grounding resistance should be in line with its minimum requirements.
AC work grounding: a point in the power system, directly or by special equipment (such as impedance, resistance, etc.) and the earth for the metal connection, known as work grounding. Work grounding mainly refers to the transformer neutral point or neutral (N line) grounding.
The N-wire must be insulated with a copper core. There are auxiliary equipotential terminals in the power distribution, equipotential terminals are generally in the box cabinet.
It must be noted that the terminal can not be exposed; can not be mixed with other grounding systems, such as DC grounding, shielding grounding, anti-static grounding, etc.; and can not be connected to the PE line. In the high-voltage system, the neutral grounding method can make the grounding relay protection accurate action and eliminate single-phase arc grounding overvoltage.
Neutral grounding can prevent the zero sequence voltage offset, to maintain the basic balance of three-phase voltage, which is very meaningful for low-voltage systems, can facilitate the use of single-phase power. Safety grounding: safety grounding is the non-electrified metal part of the electrical equipment and grounding body for a good metal connection.
That is, the building's electrical equipment and equipment near some of the metal components, with PE wire connection, but it is strictly prohibited to PE wire and N line connection. Shielded grounding and anti-static grounding: In order to avoid the use of equipment dysfunction, to avoid even the equipment damage that will occur, the equipment that constitutes the wiring system should be able to prevent the internal self-conduction and external interference.
These interferences occur either because of the coupling phenomenon between the wires, or because of capacitive or inductive effects. Its main sources are ultra-high voltage, high-power amplitude electromagnetic fields, natural lightning strikes and electrostatic discharges.
These phenomena can cause significant interference to equipment designed to send or receive very high transmission frequencies. Therefore, these devices and their cabling must be protected from interference from all sources.
Shielding and its proper grounding are the best protection against electromagnetic interference. The equipment shell can be connected to the PE line; the shielding of the conductor grounding requirements shielding piping ends and PE lines are reliably connected; indoor shielding should also be multi-point and PE lines are reliably connected.
Anti-static interference is also very important. In a clean, dry room, people walking, moving equipment, each friction will produce a lot of static electricity.
For example, in a relative humidity of 10 ~ 20% of the environment, people walking can accumulate 3. 5 million volts of electrostatic voltage, if there is no good grounding, not only will produce interference with electronic equipment, and even equipment chip damage.
The static charged objects or objects that may generate static electricity (non-insulator) through the conductive body and the earth constitute an electrical circuit grounding called anti-static grounding. Anti-static grounding requirements in a clean, quiet and dry environment, all equipment shell and indoor (including floor) facilities must be connected to the PE wire multi-point reliable.
The grounding resistance of the building's grounding device is as small as possible, independent lightning protection grounding resistance should be ≤ 10 Ω; independent safety protection grounding resistance should be ≤ 4 Ω; independent AC grounding resistance should be ≤ 4 Ω; independent DC grounding resistance should be ≤ 4 Ω; anti-static grounding resistance is generally required to ≤ 100 Ω. It is desirable to use a total **** the same grounding device, that is, the unity of the grounding body.
The unified grounding body is the ground potential reference point, thus.
6. Lightning protection and grounding
First, the AC power supply system of lightning protection and grounding general requirements 1, the AC power supply system of the mobile communication station should be used three-phase five-wire power supply.
2, mobile communication stations should be set up special power transformers, power lines should be used with a metal sheath or insulated sheath cable through the steel pipe buried into the mobile communication station, power cable metal sheath or steel pipe ends should be close to the reliable grounding. 3, when the power transformer is located outside the station, for the location of annual thunderstorms greater than 20 days, earth resistivity greater than 100Ω - m, the power line should be in the lightning protection line within the 25 ° angle protection, lightning protection line (except the terminal pole) should be made for each pole for the first time for the grounding, as shown in the figure.
In order to ensure safety, it is appropriate to install an additional set of zinc oxide lightning arrester in the lightning line terminal pole of the previous pole. If the station has been built to transform the lightning protection of overhead high-voltage power lines using lightning line is difficult, in the overhead high-voltage power lines terminal pole, terminal pole before the first, third or second, fourth pole each additional set of zinc oxide lightning arrester, while in the third pole or the fourth pole an additional set of high-voltage fuses.
Lightning line and lightning arrester grounding body should be designed into a radial shape or ring. 4, when the power transformer is located in the station, its high-voltage power lines should be used power cables from the underground into the station, the cable length should not be less than 200m, power cables and overhead power lines connected to the three phase lines should be installed zinc oxide lightning arrester, the cable ends of the metal sheath should be close to the ground.
5, mobile communication base station AC power transformer high-voltage side of the three phase lines, respectively, should be close to the ground to add zinc oxide lightning arrester, power transformer low-voltage side of the three phase lines should be added to the ground to add a gapless zinc oxide lightning arrester, transformer enclosure ﹑ low-voltage side of the AC zero, as well as power cables connected to the transformer's metal sheathing should be close to grounding. All power lines in and out of the base station should be installed at the exit of the lightning arrester.
6, into the mobile base station of low-voltage power cables should be introduced from the ground into the room, the length of which is not less than 50m (when the high-voltage side of the transformer has been used power cables, low-voltage side of the length of power cables is not limited). Power cables should be installed in the room into the AC screen lightning arrester, the zero line leading from the screen is not repeated grounding.
7, mobile communication base station power supply equipment, the normal non-electrified metal parts ﹑ lightning arrester grounding, should be made for the protection of grounding, is strictly prohibited for zero protection. 8, mobile communication base station DC work, should be from the indoor grounding convergence line close to the lead, grounding line cross-sectional area should meet the requirements of the maximum load, generally 35-95m2, the material for the multi-stranded copper wire.
9, mobile communication base station power supply equipment should meet the relevant standards ﹑ norms on lightning impact resistance index, AC screen, rectifier (or high-frequency switching power supply) should be equipped with graded protection devices, as shown. 10, leading to the distribution screen of the three phase and zero line recommended the use of French CITFL company produced by the power supply lightning box DS150E (140KA8/20us), its response time is fast (25ns), low residual voltage (700V-800V), the internal structure of the lightning box for the two poles of the MOV by the de-inductive link to the composite lightning box, which is generally installed in the low-voltage power distribution cabinets.
Don't want to emphasize that the screen AC zero line is not repeated grounding. The building is placed in the AC power line in the neutral (zero) convergence row should be insulated with the normal non-electrified metal part of the rack.
11, the distribution panel of each branch switch should also be connected to the appropriate type of power arrester, switch rated load over 200A, it is recommended to use DS150E (140KA) or LA60-B (10/350us70KA); 100A-200A between the recommended DS100R or V25B (100KA), 100A-63A is recommended to use DS70B or V20B (100KA). DS70B or V20C/4(70KA) is recommended for 100A-200A, DS44 or V20C/2(40KA) is recommended for 100A-63A. 12, important power equipment (such as UPS, rectifier, high-frequency switching power supply, precision air conditioning, etc.) of the AC inlet side also according to its capacity with different types of power arrester (DS150E-DS44 or LA60-B-V20C/2).
13, communication power supply or high-frequency switching power supply on the DC side, it is recommended to use? Complaints of BO products V20C/0-75V low-voltage lightning arrester for protection.
7.
7. Lightning tower lightning protection necessary and what precautions
Lightning tower, also known as lightning tower, extinction of lightning tower, according to the use of the differences in materials, can be divided into round steel and angle to restrain lightning tower lightning tower, according to the results of the differences can be divided into the line tower lightning tower and two, rounding off for the lightning tower is commonly utilized, because of its low cost.
Lightning tower tension for communication base stations, radar stations, airports, oil depots, small smart phone base stations and all kinds of cloud cover and roof structures, power plants, forests, kerosene depots, scenic stations, factory workshops, paper mills, and other intense places. All kinds of mining configuration project, is an oil refinery, gas station, chemical plants, coal mines, the placement of lightning tower time, due to climate change, lightning disasters continue to aggravate, many structures placed lightning tower, restraining tower roof stainless steel decorations, the situation and boldness of a variety of forms and shapes are elegant, commonly used in all kinds of structures on the roof, plaza and green space, such as residential structures, so that the structures reflect each other for the city's decorative landmarks! The building is a landmark of the city's decoration.