First of all, the lightning protection short circuit can almost use the steel bars in the building foundation as the short circuit body, but it is necessary to weld the steel bars together, and use the vertical steel bars in the building column as the down lead, which is always connected to the roof lightning protection facilities.

Secondly, many people who refuse to lead out one more steel bar are used for artificial short circuit, only when the short circuit of the building foundation itself cannot exceed the specified resistance rejection, and even so, the effect is much worse than using the building foundation itself as a short circuit body. Therefore, it is necessary to use building foundation reinforcement as short circuit body.

Concern: 1. Carry out good electrical penetration of foundation reinforcement, at least ensure that the excircle is completely penetrated. The recommended bridging material is 12MM round steel, and the welding length is about 150 mm. The average spacing between down conductors should be more than 25m. If the house is not big, it is good to have a down lead in every corner.

3. It is recommended to use two16mm steel bars or four14mm steel bars for each down lead. Ensure that the down lead is connected with the short circuit body and the roof lightning protection device.

2. How to debug lightning protection grounding?

Should the grounding grid, bus and grounding electrode be debugged? Answer: The debugging of grounding device is mainly to test the grounding resistance value of grounding device to determine whether the grounding device meets the engineering design requirements.

(1) Calculation of engineering quantity The unit of measurement for independent grounding device debugging is "group" and the unit of measurement for grounding grid is "system", and the engineering quantity is calculated according to the quantity shown in the construction drawing. (2) This norm is applicable to the debugging of grounding device, which is divided into independent grounding device debugging and grounding grid debugging, and the corresponding norm subtitle is used when using.

(3) The following problems should be paid attention to during debugging: 1) Independent grounding devices are counted as "groups". For example, a transformer on a column has an independent grounding device, which is tested once and counted as a group. 2) For the determination of grounding resistance of lightning rods, each lightning rod has a separate grounding grid (including independent lightning rods and chimney lightning rods, etc.). ), which are calculated as a group.

3) Determination of grounding resistance of grounding grid, and calculation of mother grid connected to power plant or substation as a system; An independent grounding network, whose mother network is not connected with the factory mother network, should be calculated as a system. When the grounding grid of the independent substation in the factory is not connected with the main grid of the factory, it should be calculated as a system. Large buildings have their own grounding grid (grounding resistance value is required in design). Although grounding grids will eventually be connected together, they should be calculated as a system.

4) The Grounding Device Debugging Quota is applicable to the grounding device debugging of all electrical equipment installation projects.

3. Why can lightning rod prevent lightning strike?

Lightning is a common weather phenomenon in summer.

Dazzling lightning and rumbling thunder not only make people feel scared, but also make people curious about them. Through modern scientific research, people have revealed the secret of lightning.

It turns out that lightning is a spark discharge phenomenon between clouds and between clouds and air. Lightning and thunder always happen at the same time, collectively known as lightning.

Lightning is closely related to our life. Lightning can make nitrogen, oxygen and other gases in the air have a series of chemical reactions, and the new substances formed are mixed with rainwater, and the inorganic substances falling on the ground and in the soil synthesize new nitrogen fertilizers that can be absorbed by plants.

According to the determination, about 400 million tons of nitrogen fertilizer can be synthesized by thunderstorms on the earth every year. Lightning is not only beneficial to biological growth, but also can purify the air.

Lightning can also eliminate viruses and germs in the air and reduce the occurrence of crop diseases and insect pests. But lightning can also bring disaster. For example, when the climate is dry, lightning can cause forest fires, sometimes attack people and sometimes destroy buildings ... For a long time, people have been looking for ways to suppress lightning and reduce disasters.

/kloc-In the 8th century, American scientist Franklin invented the lightning rod. It is to erect a copper rod with a sharp tip on a tall building, and then connect a metal wire, and the other end of the wire is buried underground.

In this way, the negative charge in the cloud will be conducted to the ground along this device, which can avoid the harm caused by lightning.

4. What is the knowledge about lightning protection?

Generally speaking, places with low soil resistivity and obvious changes in soil resistivity are prone to lightning strikes.

Areas with metal deposits, river beds, underground outlets, hillsides bordering rice fields, hillsides and foothills, rivers, lakes, coasts, low-lying areas and places with high groundwater levels are all vulnerable to lightning strikes. Some isolated tall buildings (structures) such as iron towers and chimneys are also vulnerable to lightning strikes.

When a thunderstorm comes, because the trees are taller, they are vulnerable to lightning. Stay away from trees in thunderstorm weather, and try to squat down with your feet together.

Why does the bathroom become a high lightning strike area at home? The water pipes in the bathroom are mostly metal bodies with strong conductivity, so the bathroom naturally becomes a lightning strike-prone area at home in thunderstorm days. Moreover, the solar water heaters installed on the roofs of most citizens are not connected with lightning protection equipment.

Some solar water heaters are equipped with high iron frames for good lighting. In the case of thunder, the water heater may become a "lightning rod", causing lightning strikes. How to prevent electric shock accidents: 1 in bad weather.

In strong winds, thunderstorms and other bad weather, we should try to reduce going out. If you have to go out and walk, observe the terrain carefully, walk carefully and avoid stepping on wires.

Avoid walking around power facilities such as telephone poles and iron towers, and bypass fallen wires. 2。

Don't walk barefoot when going out. 3。

Indoor, in case of thunderstorm and windy weather, turn off the running household appliances in time and unplug the power plug; Don't go barefoot to repair live lines or equipment at home; If the home is accidentally flooded, the power supply should be cut off immediately to prevent the household appliances being used from accidents due to water ingress and insulation damage. 4。

When walking outdoors in rainy days, you should pay attention to observation, avoid touching the metal parts of street lamp poles, signal lamp poles and landing billboards, and detour where there is water. 5。

When it is found that power facilities such as distribution panels and box-type substations are flooded, it is necessary to inform the power supply department in time to deal with them, and at the same time stay away from other personnel. How to give first aid after being struck by lightning The following measures can be taken to give first aid after being struck by lightning: 1.

The injured person lies flat on the spot, unbuttoning buttons, belts, etc. 2。

Immediately perform mouth-to-mouth resuscitation and chest compressions until the patient wakes up. 3。

Holding hands or acupoints, such as Renzhong, Xuan Shi, Yongquan and Mingmen. 4。

Send to the hospital for emergency treatment. Don't shelter from the rain under the tree during a thunderstorm.

Don't go into the hut during a thunderstorm. Don't overload the power cord.

Don't wipe the lamp holder with wet hands and wet cloth. The air is humid in thunderstorm season, which is the season of frequent electric shock accidents. The public should replace the old or damaged wires in time to prevent accidents such as upside down and leakage that harm personal safety.

Relevant experts answered questions about lightning protection, prevention of accidental electric shock, safe use of electricity, electric shock first aid and other knowledge. Some people think that as long as lightning rods and lightning belts are installed in buildings, people and equipment in buildings will not be struck by lightning.

This view is wrong. First of all, the lightning rod has a certain protection range. When the building is beyond the protection range of lightning rod, it is not protected by lightning rod.

Secondly, whether the performance of lightning rod meets the technical requirements, such as material specifications and grounding resistance. If it loses its function due to disrepair, it will not only fail to achieve the lightning protection effect, but will increase the probability of being struck by lightning. Furthermore, lightning rods can only protect buildings from lightning strikes, but not people and equipment in buildings from lightning strikes.

Lightning rods can only release 50% of lightning energy to the ground, and the remaining 50% will be released to the ground through various pipelines and equipment through induction and energy coupling. What should I pay attention to when encountering strong lightning? Pay attention to the following points when encountering lightning: 1.

If you happen to be at home when there is strong lightning, it is recommended not to venture out. Don't use radios and televisions with external antennas, and don't answer the phone.

2。 If you are in the wild, you should immediately look for shelter, and take concrete buildings with lightning rods, steel frames or steel plates as lightning protection places, and vehicles with complete metal compartments can also be used.

3。 When there is no shelter, don't go near empty places or lonely trees on the top of the mountain. These places are most vulnerable to lightning strikes.

Don't stay in open waters and boats; Try to avoid tall trees and forest edges, around wires and flagpoles, and near high objects without lightning protection equipment, such as haystacks and tents. Don't get close to huge metal objects such as railway tracks and long metal railings, and don't stay at the top of the mountain and commanding heights. 4。

During the lightning, it is best not to ride horses, bicycles or motorcycles; Don't carry metal objects in the open air; Do not go near any part of lightning protection equipment. 5。

If you can't find a suitable lightning protection place, try to reduce the center of gravity and the contact area between the human body and the ground. You can squat down, put your feet together, put your hands on your knees, lean forward, and never lie on the ground, trenches or pits. If you can wear a raincoat, the lightning protection effect will be better. People in the wild, whether moving or static, should be separated by a few meters, not crowded together, or they can hide in bigger caves.

6。 Note that when your hair stands up or your skin vibrates, you may be struck by lightning, so you should fall to the ground immediately.

People who are struck by lightning may be burned or severely shocked, but they will not be charged and can be rescued safely. 7。

Never use your cell phone when it's thundering! What is the key to personal lightning protection? Personal lightning protection should pay attention to the following points: 1. You should stay indoors and close the doors and windows; People who work outdoors should hide in buildings.

2。 It is not appropriate to use TV, audio and other electrical appliances without lightning protection measures or insufficient lightning protection measures, and it is not appropriate to use faucets.

3。 Do not touch antennas, water pipes, barbed wire, metal doors and windows, external walls of buildings, and stay away from live equipment such as wires or other similar metal devices.

4。 Reduce the use of telephones and mobile phones.

5。 Do not swim or engage in other water sports. Not suitable for outdoor ball games. Leave water and other empty places to find shelter.

6。 Don't stand near mountain tops, roofs or other highly conductive objects.

7。 Do not handle flammable items in open containers.

8。 Stay away from trees and masts when you can't hide in a building with lightning protection facilities in the wild.

9。 It is not advisable to take an umbrella in an open field, nor to carry badminton rackets and golf clubs on your shoulders.

10。 It is not advisable to drive a motorcycle or ride a bike.

How to prevent electric shock accidents and measures to prevent electrical fire accidents?

5. What is the grounding device?

Lightning protection In order to prevent lightning damage, lightning protection devices must be strictly prevented.

A complete lightning protection device consists of lightning receptor (lightning rod), down conductor and grounding body. Lightning arrester is a metal conductor that directly receives lightning strikes. It is installed on the top of the protected object or on an independent lightning arrester.

In the initial development stage of lightning tunnel, because Lei Yun is relatively high from the ground, the development direction of the tunnel is not affected by ground objects, but when the lightning tunnel develops to a certain height, the protrusions on the ground will affect the development direction of the tunnel. Therefore, lightning arresters (lightning rods) must be installed in the storage areas of inflammable and explosive chemicals such as warehouses and oil tanks, and the passages will develop in the direction of lightning rods. This is because the arrester is higher than the storage protrusion of flammable and explosive chemicals and has a good grounding.

Therefore, the essential function of lightning arrester is to lead lightning to itself and lightning current to the earth safely. The down lead of the grounding device is a metal conductor connecting the lightning receptor and the grounding device, and its function is to transmit the lightning current on the lightning receptor to the grounding body. The down conductor is generally made of round steel or flat steel. If there are corrosive places, the cross-sectional area should be appropriately increased, and the down conductor should be laid along the external wall of the building. The laying route should be as short and straight as possible, and the fixed fulcrum should not be greater than 1.

5 to 2 meters. In order to prevent foreign bodies from causing mechanical damage and corrosion to the down lead, steel pipes should be used at the grounding connection.

For the convenience of inspection and measurement, above the ground 1. 5- 1。

The disconnect card must be set at 8 meters. Grounding body includes grounding device and soil or concrete around the device, and its function is to effectively drain lightning current into the earth. Now commonly used grounding devices are horizontal grounding electrode, vertical grounding electrode, extended grounding electrode and foundation grounding electrode.

The grounding device of flammable and explosive chemicals generally adopts vertical grounding electrode, that is, a 2. Angle steel, round steel, steel pipe or copper column profile over 5 meters are made and driven vertically into the soil. When the grounding can't meet the requirements, ring grounding electrode group and radial grounding electrode group can be used. In order to prevent corrosion, preservatives can be applied before burial.

In some areas, the soil resistance is high, and the general grounding method can not meet the requirements of grounding design. Artificial methods can be used to reduce the resistivity of grounded soil, that is, soil replacement or chemical treatment. What are the grounding requirements for lightning protection grounding? Lightning protection grounding: In order to quickly introduce lightning current into the earth and prevent lightning damage, grounding is called lightning protection grounding.

Most buildings belong to Class I load and should be designed according to the protection measures of Class I lightning protection buildings. The lightning arrester adopts pin-belt combined lightning arrester, and the lightning protection belt adopts 25*4(mm) galvanized flat steel to form a grid of ≤ 10* 10(m) on the roof. The grid is electrically connected with the roof metal components and the steel bars in the column head of the building, and the down lead is wound by the steel bars in the column head. This can not only effectively prevent lightning from damaging the equipment in the building, but also prevent external electromagnetic interference.

The power frequency grounding resistance of various lightning protection grounding devices should generally be determined according to the counterattack conditions when lightning strikes. If the lightning protection device and the working grounding of electrical equipment share a total grounding grid, the grounding resistance should meet the minimum requirements.

AC working grounding: A point in the power system is connected to the earth directly by metal or through special equipment (such as impedance and resistance), which is called working grounding. Working grounding mainly refers to the neutral point or neutral line (N line) grounding of transformer.

N-wire must be insulated with copper core. There are auxiliary equipotential terminals in power distribution, which are generally in the cabinet.

It must be noted that the terminal cannot be exposed; Can not be mixed with other grounding systems, such as DC grounding, shielding grounding, anti-static grounding, etc. You can't connect the PE line either. In high voltage system, neutral grounding can make grounding relay protection work accurately and eliminate single-phase arc grounding overvoltage.

Neutral grounding can prevent zero-sequence voltage deviation and keep the three-phase voltage basically balanced, which is very meaningful for low-voltage systems and can facilitate the use of single-phase power supply. Safety protection grounding: Safety protection grounding is to connect the uncharged metal parts of electrical equipment with the grounding body.

That is, the electrical equipment in the building and some metal components near the equipment are connected with PE wires, but it is forbidden to connect PE wires with N wires. Shielded grounding and anti-static grounding: In order to avoid the malfunction or even damage of the equipment used, the equipment constituting the wiring system should be able to prevent internal self-conduction and external interference.

These interferences are either caused by the coupling phenomenon between wires, or by the capacitance effect or inductance effect. Its main sources are ultra-high voltage, high-power radiated electromagnetic field, natural lightning strike and electrostatic discharge.

These phenomena will cause great interference to the equipment designed to send or receive high transmission frequency. Therefore, these devices and their wiring must be protected from interference from all sides.

Shielding and its correct grounding are the best protection methods to prevent electromagnetic interference. The equipment shell can be connected with PE wire; The shielded grounding of conductor requires that both ends of shielded pipeline be reliably connected with PE line; Indoor shielding should also be reliably connected with PE line at multiple points.

Anti-static interference is also very important. In a clean and dry room, people will generate a lot of static electricity when walking and moving equipment rub against each other.

For example, in an environment with relative humidity of 10~20%, people can accumulate 3. The electrostatic voltage of 50 thousand volts, without good grounding, will not only interfere with electronic equipment, but even damage the chip of the equipment.

Electrostatic objects or objects (non-insulators) that may generate static electricity form a circuit with the earth through electrostatic conductors, which is called anti-static grounding. Anti-static grounding requires that all equipment enclosures and indoor (including ground) facilities must be reliably connected to PE lines in a clean and dry environment.

The smaller the grounding resistance of building grounding device, the better. Independent lightning protection grounding resistance should be ≤10Ω; The grounding resistance of independent safety protection shall be ≤ 4Ω; Independent AC working grounding resistance should be ≤ 4Ω; Independent DC working grounding resistance should be ≤ 4Ω; Anti-static grounding resistance generally requires ≤100Ω. General * * * common grounding device, namely unified grounding body, should be adopted.

Unified grounding body is the reference point of grounding potential, therefore.

6. Lightning protection and grounding engineering

1. General requirements for lightning protection and grounding of AC power supply system 1. The AC power supply system of mobile communication station should adopt three-phase five-wire power supply mode.

2. The mobile communication station should be equipped with a special power transformer, and the power cord should be introduced into the mobile communication station through a steel pipe with a metal sheath or an insulating sheath. Both ends of metal sheath or steel pipe of power cable shall be reliably grounded nearby. 3. When the power transformer is located outside the station, if the annual thunderstorm day is more than 20 days and the earth resistivity is greater than100Ω m, the power line should be within the protection range of 25 degrees of the lightning conductor, and each pole of the lightning conductor (except the terminal pole) should be grounded once, as shown in the figure.

In order to ensure safety, a set of zinc oxide arresters should be installed on the front pole of the terminal pole of lightning rod. If it is difficult to use lightning rods in the lightning protection reconstruction of the existing overhead high-voltage power lines, a set of zinc oxide arresters can be installed on the terminal poles of the overhead high-voltage power lines, and a set of high-voltage fuses can be installed on the roof of the world or the fourth pole in front of the terminal poles.

The grounding body of lightning rod and lightning arrester should be designed as radial or annular. 4. When the power transformer is located in the station, its high-voltage power line should be powered by power cable from underground, and the length of the cable should not be less than 200 m. The three-phase conductor at the joint of the power cable and the overhead power line should be equipped with zinc oxide arrester, and the metal outer sheath at both ends of the cable should be grounded nearby.

5. In the mobile communication base station, the three-phase conductor on the high-voltage side of the AC power transformer should be equipped with zinc oxide arrester to the ground nearby, and the three-phase conductor on the low-voltage side of the power transformer should be equipped with gapless zinc oxide arrester to the ground respectively. The shell of the transformer, the AC neutral wire on the low voltage side and the metal outer sheath of the power cable connected with the transformer shall be grounded nearby. Lightning arresters should be installed at all power line exits in and out of the base station.

6. The low-voltage power cable entering the mobile communication base station should be introduced into the computer room from underground, and its length should be not less than 50m (when the power cable is used on the high-voltage side of the transformer, the length of the power cable on the low-voltage side is not limited). Lightning arrester should be installed at the AC screen of power cable entering the machine room, and the zero line led from the screen should not be grounded repeatedly.

7. The normally uncharged metal parts of the power supply equipment of the mobile communication base station and the grounding terminal of the lightning arrester should be protected and grounded, and zero protection is prohibited. 8. The DC working place of the mobile communication base station should be connected from the indoor grounding hub nearby. The cross-sectional area of grounding wire should meet the requirements of maximum load, generally 35-95m2, and the material is multi-strand copper wire.

9. The power supply equipment of the mobile communication base station shall meet the requirements of relevant standards and specifications for lightning impulse resistance, and the AC screen, rectifier (or high-frequency switching power supply) shall be provided with classified protection devices, as shown in the figure. 10, the three-phase line and the zero line leading to the distribution panel are recommended to adopt the power supply lightning box ds150e (140ka8/20us) produced by French CITFL, with fast response time (25ns) and low residual voltage (700V-800V). The internal structure of lightning protection box is that two MOVs are connected by desensitization.

Don't emphasize that the AC neutral line in the screen is not repeatedly grounded. The neutral line (neutral line) bus bar in the AC power line laid in the building should be insulated from the normally uncharged metal part of the rack.

1 1, each switch in the distribution panel should also be equipped with a corresponding type of power arrester, and the rated load of the switch exceeds 200A. It is recommended to adopt DS 150E( 140KA) or LA60-B (10/350US70ka); 100A-200A, recommended DS 100R or V25B (100ka), 100a-63a, recommended DS70B or v20c/4 (70ka); DS44 or V20C/2(40KA) should be used below 50A. 12, AC incoming terminals of important electrical equipment (such as UPS, rectifier, high-frequency switching power supply, precision air conditioning, etc.). ) Different types of power arresters (DS 150E-DS44 or LA60-B-V20C/2) are also used according to the capacity.

13, DC communication power supply or high-frequency switching power supply, which is better recommended? The protection of V20C/0-75V low-voltage lightning arrester. .

7. What are the necessity and precautions for lightning protection of lightning protection towers?

Lightning protection towers are also called lightning protection towers and lightning protection towers. According to the different materials used to restrain lightning protection towers, they can be divided into round steel and angle steel, and according to the different results, they can be divided into wire towers, lightning rod towers and two kinds. Round steel is commonly used in lightning protection towers because of its low cost.

Lightning towers are used in communication base stations, radar stations, airports, oil depots, PHS base stations, various cloud shelters and roof construction, power plants, forests, kerosene depots, scene stations, factory workshops, paper mills and other tense places. All kinds of mine configuration projects are when lightning protection towers are installed in refineries, gas stations, chemical plants and coal mines. Due to climate change, lightning disasters are becoming more and more serious. Many structures are equipped with lightning protection towers to restrain the stainless steel decoration on the top of the lightning protection towers. The situation and courage are diverse, and the appearance is elegant. Widely used in various roofs, squares, green spaces, such as residential buildings, so that the buildings complement each other and become a landmark building for urban decoration.