In 1750, Franklin proposed to use a lightning rod that discharges charges slowly at the needle tip to neutralize the charge in the thundercloud and use it for lightning protection. Later practice proved that it could not "avoid lightning," but guided the mine to protect its surrounding equipment. Afterwards, Russia’s Lomonosov issued a paper in 1753 after repeating Franklin’s famous kite test (his friend Lichman experimented with him and was sacrificed by the lightning stroke hit by direct lightning). In the speech of the atmospheric phenomena generated by electricity, an important argument was also made. A little-known important fact is that shortly after Franklin published the theory of lightning rods, an engineer in France established a lightning rod according to his theory, and it quickly took off. This is the first time that humans have actively tried to change the lightning flash route, and it is also a proof that direct lightning can be protected. The French engineer, as an upright scientist, was pleased to report the lightning success of the Franklin lightning rod.
The practical application of lightning rods must solve the problem of its protection scope. This is gradually quantified for many years in laboratories and practical applications, and its accuracy has basically met the needs of engineering design. It is the development of high-voltage transmission and power systems in various countries that has driven this research work forward.
In 1925-1926, Peek first used an impulse voltage generator in a laboratory to cause “artificial lightning†to discharge the lightning rod model and to study the protection scope—the relationship between the protection coefficient and the ratio of thundercloud height to needle height (H/h). , and studied the effect of thundercloud polarity on the protection factor. In 1930-1934, countries began to use lightning rods to protect power plants and substations. At that time, the 230KV power grid had appeared for many years, and the 287KV ultra-high voltage power grid was under construction. For example, in 1934, the United States Gas and Electric Power Company (AGE) began to use lightning rods and lightning conductors to protect substations. The scope of protection of the lightning conductors is determined as follows: When the structure is strong enough, the horizontal distance of each protection is 0.45m. Raise the height by 0.3m; when the strength of the structure is limited, the height of each protection level is 0.6m and 0.3m is raised. This corresponds to 56° and 64° protection angle, respectively. This is similar to the 60° lightning protection standard in Japan in the late 1960s. By the early 1960s (Davis, 1963) and the early 1970s, the protection scope of the lightning protection lines for the protection of transmission lines had successively proposed a strike range theory, ie, the protection range was selected in consideration of the magnitude of the lightning current amplitude. China's high-voltage workers (professor Zhu Mumei directed Comrade Wang Xiaoyu) also proposed a similar method when studying the lightning protection of transmission lines from 1962 to 1964. As for the protection of power plants and substations, in the 1950s, China used only lightning rods for fear of lightning line breakage affecting the whole plant and the entire substation. By the mid-1970s, it was clear that the lightning protection line could be used for the protection of power plants and substations.
Lightning Protection Strips Grounding conductors are laid around the ridges and roofs of buildings and are developed from lightning rods and lightning conductors. The author first learned about this technique from German sources. The lightning protection net is laid with a grounding conductor in the middle of the lightning protection zone to protect the middle part of the building. For the protection of buildings, its advantages are easy to install, low cost, and compared with towering lightning rods, the probability of lightning is greatly reduced. Moreover, after it is flashed, it is generally caused by multiple lead wires to discharge the current, and the counter-attack voltage on the indoor equipment is relatively low. The cage-type lightning protection method proposed by China's construction lightning protection workers and widely used throughout the country is the use of the Faraday cage formed by building steel reinforcement. At the same time, it also solves the problem of equipotential bonding, which greatly improves the reliability of building lightning protection. In addition, it also facilitates uniform grounding (co-location) of electricity, telecommunications, and electrical facilities inside the cage (inside the house). China's power sector power plant plant, computer room, substation and main control room, including control and signal cables and other voltage equipment for different purposes, and the development of 1952,1956 versions of the over-voltage and grounding standards. This is more than 40 years earlier than the uniform earthing and equipotential bonding that IEC regulations in recent years and foreign companies widely publicize.
Attempts have been made to increase the use of radioactive materials on the tip of the needle to increase the effect of lightning, extend the scope of protection, and later prove ineffective. In the late 1960s and early 1970s, the lightning protection codes for buildings in the UK, Germany, and other countries have explicitly negated the conclusions. In the 1980s, the tests conducted by the Institute of Electric Power of the Ministry of Water Resources and Electric Power in high-voltage test rooms also proved that there was no difference in the effect of the lightning rod with the same size of ordinary lightning rod. China's overvoltage and insulation coordination standards have always held a negative attitude toward it. Despite international conclusions, there are still some places in France and some French-speaking countries that continue to use lightning rods with radiation. Some industrial equipment imported from French-speaking countries in our country is protected by such lightning rods. This is not only a waste of funds, it does not contribute to the improvement of mine protection, and it also causes personal environmental hazards due to its radioactive materials. It violates all of our national standards for lightning protection.
The working principle of discharging the lightning arrester in advance The working principle of discharging the lightning arrester in advance is to produce an upward pilot that is faster than ordinary lightning rods. This description is based on the negative polarity of the discharge in the case of this type of discharge is the most universal.
How the unit conducts lightning disaster protection 1. The unit shall regularly detect the lightning protection facilities by professional lightning protection companies and assess whether the lightning protection facilities meet the requirements of the national regulations, such as schools, companies, hospitals above the district level, hotels above the four-star level, and urban areas. High-rise buildings with a height of 45 meters or more need to be tested once every two years.
2. The unit shall establish a person responsible for preventing lightning disasters, be responsible for lightning protection safety work, establish various lightning protection safety work, establish regular inspections of various lightning protection facilities, check after thunderstorms, and daily maintenance. After a thunderstorm, the overvoltage protector installed on the power supply of the telephone program control switch, computer and other electrical equipment and on the signal line should be checked for damage, and should be promptly replaced when found damaged.
3. During the design and construction of lightning protection facilities, the construction unit shall consider comprehensively the factors of geology, soil, meteorology, environment, and the characteristics of the objects to be protected, and the rules of thunder and lightning activity, and adopt safe, reliable, technologically advanced, and economically reasonable design and construction. .
4. Lightning protection equipment, devices and equipment that meet the national standards for technology and quality should be used, and non-standard lightning protection products and devices should be avoided.
5. The newly added construction and newly added installation equipment should simultaneously redesign and construct the lightning protection system. For example, the re-laying of computer network cables, the shifting and elevation of outdoor antennas, etc. should all be redesigned and constructed.
6. When a thunderstorm occurs, it shall be promptly dealt with and measures taken to avoid further lightning strikes.
The overall concept of lightning protection The six-point lightning protection plan addresses the hazards of lightning. We believe that lightning protection must be comprehensive. It mainly includes the following six aspects:
A Controlling the point of lightning strike (using a lightning rod with a large protection range)
B. Safe guidance of lightning current into the ground network C. Perfect low-impedance ground network D Elimination of ground loop E Surge protection of power supply F Signal and data line transient protection 1> Flashing lightning is to allow lightning energy within a certain range According to the channel designed by people to vent to the earth. The safety of terrestrial communication stations depends to a large extent on the ability to use an effective lightning catcher to capture a lightning discharge of a certain protection range and incorporate it into a pre-designed rational approach to ground discharge. The lightning rod is an active lightning receiving device. Its English name is Lightning Conductor. It is intended to be a lightning guide. Its function is to guide lightning current into the earth. Lightning conductors and lightning conductors have been developed on the basis of lightning rods. The use of lightning rods is the most important and basic lightning protection measure.
2> When the lightning equalizer is connected to the lightning arrester, the down conductor immediately rises to a high potential, and a side flashover occurs around the conductor of the lightning protection system that is still at the ground potential, and the potential of the conductor is raised, and thus the personnel And equipment constitute a hazard. In order to reduce this risk of flashover, the easiest way is to use a pressure equalizing ring to connect the conductors at ground potential equal to the grounding device. Metal facilities, electrical installations and electronic equipment in the station should be connected to the lightning protection system by using thicker wires if their distance from the lightning protection system's conductors, in particular the lightning arrester, does not meet the required safety requirements. Make equipotential bonding. In this way, when the lightning current passes, all the facilities in the station immediately form an “equipotential island†to ensure that there is no harmful potential difference between the conductive parts, and no side flashover discharge occurs. The perfect equipotential bonding also prevents the counterattack caused by the rise in ground potential caused by lightning currents.
3> Grounding Grounding is to allow the lightning energy that has been incorporated into the lightning protection system to be discharged into the earth. A good grounding can effectively reduce the voltage on the lead-off line and avoid counterattacks. In the past, some specifications required that the electronic equipment be grounded separately to prevent the stray current or transient current in the power grid from interfering with the normal operation of the equipment. Prior to the 1990s, the communications and navigation equipment of the military was mainly based on electronic tube devices and analog communications. Analog communications were particularly sensitive to interference. In order to resist interference, power supply and communications grounds were used separately. At present, the grounding of lightning protection does not advocate separate grounding. In the IEC standard and ITU-related standards are not advocating separate grounding, the US standard IEEEStd1100-1992 more pointedly pointed out: It is not recommended to use any kind of so-called separate, independent, computer, electronic or other such incorrect earth The grounding body serves as a connection point for the grounding conductor of the device. Grounding is the most basic link in lightning protection systems. Grounding is not good, and the lightning protection effect of all lightning protection measures cannot be exerted. Lightning protection grounding is the most basic safety requirement in the ground station station installation acceptance specification.
4> Shunt Shunt is an appropriate lightning arrester connected in parallel between all external wires (including power supply lines, telephone lines, signal lines, antenna feeders, etc.) and ground lines. When an overvoltage wave generated by a direct lightning or an induced lightning line along the line enters the room or the device, the resistance of the lightning arrester abruptly drops to a low value, and near the short-circuit state, the lightning current flows into the ground.
Shunting is the key to the rapid development of modern lightning protection technology and is a key measure to protect various electrical and electronic equipment. In recent years, new forms of lightning that frequently appear need to be solved in this way. Since lightning currents are shunted, there will still be a small portion of the wire that enters the equipment. This is still dangerous for high-voltage-resistant microelectronic equipment. Therefore, multi-stage shunting of such equipment before the wires enter the housing is required. .
The current research and development of lightning arresters is also beyond the scope of diversion. Some arresters can be directly connected in series on the signal line or antenna feeder. They can allow the useful signal to pass smoothly and block the lightning overvoltage wave.
When using lightning protection measures such as splitting, special attention should be paid to the selection of performance parameters of arresters, because the installation of additional facilities will more or less affect the performance of the system. For example, the access of the signal lightning arrester should not affect the transmission rate of the system; the loss of the antenna lightning arrester within the passband should be as small as possible; if it is used on an directional device, it cannot cause a positioning error.
5> Shielding shielding is the use of metal mesh, foil, shell, tube and other conductors to surround the object to be protected, blocking the lightning pulse electromagnetic field from the space intrusion channel. Shielding is the most effective way to prevent lightning electromagnetic pulse radiation from affecting electronic devices.
The practical application of lightning rods must solve the problem of its protection scope. This is gradually quantified for many years in laboratories and practical applications, and its accuracy has basically met the needs of engineering design. It is the development of high-voltage transmission and power systems in various countries that has driven this research work forward.
In 1925-1926, Peek first used an impulse voltage generator in a laboratory to cause “artificial lightning†to discharge the lightning rod model and to study the protection scope—the relationship between the protection coefficient and the ratio of thundercloud height to needle height (H/h). , and studied the effect of thundercloud polarity on the protection factor. In 1930-1934, countries began to use lightning rods to protect power plants and substations. At that time, the 230KV power grid had appeared for many years, and the 287KV ultra-high voltage power grid was under construction. For example, in 1934, the United States Gas and Electric Power Company (AGE) began to use lightning rods and lightning conductors to protect substations. The scope of protection of the lightning conductors is determined as follows: When the structure is strong enough, the horizontal distance of each protection is 0.45m. Raise the height by 0.3m; when the strength of the structure is limited, the height of each protection level is 0.6m and 0.3m is raised. This corresponds to 56° and 64° protection angle, respectively. This is similar to the 60° lightning protection standard in Japan in the late 1960s. By the early 1960s (Davis, 1963) and the early 1970s, the protection scope of the lightning protection lines for the protection of transmission lines had successively proposed a strike range theory, ie, the protection range was selected in consideration of the magnitude of the lightning current amplitude. China's high-voltage workers (professor Zhu Mumei directed Comrade Wang Xiaoyu) also proposed a similar method when studying the lightning protection of transmission lines from 1962 to 1964. As for the protection of power plants and substations, in the 1950s, China used only lightning rods for fear of lightning line breakage affecting the whole plant and the entire substation. By the mid-1970s, it was clear that the lightning protection line could be used for the protection of power plants and substations.
Lightning Protection Strips Grounding conductors are laid around the ridges and roofs of buildings and are developed from lightning rods and lightning conductors. The author first learned about this technique from German sources. The lightning protection net is laid with a grounding conductor in the middle of the lightning protection zone to protect the middle part of the building. For the protection of buildings, its advantages are easy to install, low cost, and compared with towering lightning rods, the probability of lightning is greatly reduced. Moreover, after it is flashed, it is generally caused by multiple lead wires to discharge the current, and the counter-attack voltage on the indoor equipment is relatively low. The cage-type lightning protection method proposed by China's construction lightning protection workers and widely used throughout the country is the use of the Faraday cage formed by building steel reinforcement. At the same time, it also solves the problem of equipotential bonding, which greatly improves the reliability of building lightning protection. In addition, it also facilitates uniform grounding (co-location) of electricity, telecommunications, and electrical facilities inside the cage (inside the house). China's power sector power plant plant, computer room, substation and main control room, including control and signal cables and other voltage equipment for different purposes, and the development of 1952,1956 versions of the over-voltage and grounding standards. This is more than 40 years earlier than the uniform earthing and equipotential bonding that IEC regulations in recent years and foreign companies widely publicize.
Attempts have been made to increase the use of radioactive materials on the tip of the needle to increase the effect of lightning, extend the scope of protection, and later prove ineffective. In the late 1960s and early 1970s, the lightning protection codes for buildings in the UK, Germany, and other countries have explicitly negated the conclusions. In the 1980s, the tests conducted by the Institute of Electric Power of the Ministry of Water Resources and Electric Power in high-voltage test rooms also proved that there was no difference in the effect of the lightning rod with the same size of ordinary lightning rod. China's overvoltage and insulation coordination standards have always held a negative attitude toward it. Despite international conclusions, there are still some places in France and some French-speaking countries that continue to use lightning rods with radiation. Some industrial equipment imported from French-speaking countries in our country is protected by such lightning rods. This is not only a waste of funds, it does not contribute to the improvement of mine protection, and it also causes personal environmental hazards due to its radioactive materials. It violates all of our national standards for lightning protection.
The working principle of discharging the lightning arrester in advance The working principle of discharging the lightning arrester in advance is to produce an upward pilot that is faster than ordinary lightning rods. This description is based on the negative polarity of the discharge in the case of this type of discharge is the most universal.
How the unit conducts lightning disaster protection 1. The unit shall regularly detect the lightning protection facilities by professional lightning protection companies and assess whether the lightning protection facilities meet the requirements of the national regulations, such as schools, companies, hospitals above the district level, hotels above the four-star level, and urban areas. High-rise buildings with a height of 45 meters or more need to be tested once every two years.
2. The unit shall establish a person responsible for preventing lightning disasters, be responsible for lightning protection safety work, establish various lightning protection safety work, establish regular inspections of various lightning protection facilities, check after thunderstorms, and daily maintenance. After a thunderstorm, the overvoltage protector installed on the power supply of the telephone program control switch, computer and other electrical equipment and on the signal line should be checked for damage, and should be promptly replaced when found damaged.
3. During the design and construction of lightning protection facilities, the construction unit shall consider comprehensively the factors of geology, soil, meteorology, environment, and the characteristics of the objects to be protected, and the rules of thunder and lightning activity, and adopt safe, reliable, technologically advanced, and economically reasonable design and construction. .
4. Lightning protection equipment, devices and equipment that meet the national standards for technology and quality should be used, and non-standard lightning protection products and devices should be avoided.
5. The newly added construction and newly added installation equipment should simultaneously redesign and construct the lightning protection system. For example, the re-laying of computer network cables, the shifting and elevation of outdoor antennas, etc. should all be redesigned and constructed.
6. When a thunderstorm occurs, it shall be promptly dealt with and measures taken to avoid further lightning strikes.
The overall concept of lightning protection The six-point lightning protection plan addresses the hazards of lightning. We believe that lightning protection must be comprehensive. It mainly includes the following six aspects:
A Controlling the point of lightning strike (using a lightning rod with a large protection range)
B. Safe guidance of lightning current into the ground network C. Perfect low-impedance ground network D Elimination of ground loop E Surge protection of power supply F Signal and data line transient protection 1> Flashing lightning is to allow lightning energy within a certain range According to the channel designed by people to vent to the earth. The safety of terrestrial communication stations depends to a large extent on the ability to use an effective lightning catcher to capture a lightning discharge of a certain protection range and incorporate it into a pre-designed rational approach to ground discharge. The lightning rod is an active lightning receiving device. Its English name is Lightning Conductor. It is intended to be a lightning guide. Its function is to guide lightning current into the earth. Lightning conductors and lightning conductors have been developed on the basis of lightning rods. The use of lightning rods is the most important and basic lightning protection measure.
2> When the lightning equalizer is connected to the lightning arrester, the down conductor immediately rises to a high potential, and a side flashover occurs around the conductor of the lightning protection system that is still at the ground potential, and the potential of the conductor is raised, and thus the personnel And equipment constitute a hazard. In order to reduce this risk of flashover, the easiest way is to use a pressure equalizing ring to connect the conductors at ground potential equal to the grounding device. Metal facilities, electrical installations and electronic equipment in the station should be connected to the lightning protection system by using thicker wires if their distance from the lightning protection system's conductors, in particular the lightning arrester, does not meet the required safety requirements. Make equipotential bonding. In this way, when the lightning current passes, all the facilities in the station immediately form an “equipotential island†to ensure that there is no harmful potential difference between the conductive parts, and no side flashover discharge occurs. The perfect equipotential bonding also prevents the counterattack caused by the rise in ground potential caused by lightning currents.
3> Grounding Grounding is to allow the lightning energy that has been incorporated into the lightning protection system to be discharged into the earth. A good grounding can effectively reduce the voltage on the lead-off line and avoid counterattacks. In the past, some specifications required that the electronic equipment be grounded separately to prevent the stray current or transient current in the power grid from interfering with the normal operation of the equipment. Prior to the 1990s, the communications and navigation equipment of the military was mainly based on electronic tube devices and analog communications. Analog communications were particularly sensitive to interference. In order to resist interference, power supply and communications grounds were used separately. At present, the grounding of lightning protection does not advocate separate grounding. In the IEC standard and ITU-related standards are not advocating separate grounding, the US standard IEEEStd1100-1992 more pointedly pointed out: It is not recommended to use any kind of so-called separate, independent, computer, electronic or other such incorrect earth The grounding body serves as a connection point for the grounding conductor of the device. Grounding is the most basic link in lightning protection systems. Grounding is not good, and the lightning protection effect of all lightning protection measures cannot be exerted. Lightning protection grounding is the most basic safety requirement in the ground station station installation acceptance specification.
4> Shunt Shunt is an appropriate lightning arrester connected in parallel between all external wires (including power supply lines, telephone lines, signal lines, antenna feeders, etc.) and ground lines. When an overvoltage wave generated by a direct lightning or an induced lightning line along the line enters the room or the device, the resistance of the lightning arrester abruptly drops to a low value, and near the short-circuit state, the lightning current flows into the ground.
Shunting is the key to the rapid development of modern lightning protection technology and is a key measure to protect various electrical and electronic equipment. In recent years, new forms of lightning that frequently appear need to be solved in this way. Since lightning currents are shunted, there will still be a small portion of the wire that enters the equipment. This is still dangerous for high-voltage-resistant microelectronic equipment. Therefore, multi-stage shunting of such equipment before the wires enter the housing is required. .
The current research and development of lightning arresters is also beyond the scope of diversion. Some arresters can be directly connected in series on the signal line or antenna feeder. They can allow the useful signal to pass smoothly and block the lightning overvoltage wave.
When using lightning protection measures such as splitting, special attention should be paid to the selection of performance parameters of arresters, because the installation of additional facilities will more or less affect the performance of the system. For example, the access of the signal lightning arrester should not affect the transmission rate of the system; the loss of the antenna lightning arrester within the passband should be as small as possible; if it is used on an directional device, it cannot cause a positioning error.
5> Shielding shielding is the use of metal mesh, foil, shell, tube and other conductors to surround the object to be protected, blocking the lightning pulse electromagnetic field from the space intrusion channel. Shielding is the most effective way to prevent lightning electromagnetic pulse radiation from affecting electronic devices.
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