In the past,the lightning strike risk assessment of wind farms mainly referred to the Lightning Protection Part 2:Risk Management(IEC 62305-2-2010)and the Lightning Protection of Wind Energy System(IEC 61400-24-2019)b...In the past,the lightning strike risk assessment of wind farms mainly referred to the Lightning Protection Part 2:Risk Management(IEC 62305-2-2010)and the Lightning Protection of Wind Energy System(IEC 61400-24-2019)based on protection angle method.In fact,the basic idea of the two is the same,that is,the source of the lightning fan is replaced by S1-S4 of the former lightning building with the latter ND-NDJ.According to the above method of wind farm evaluation,it has been proved that the practice can not achieve good results.Taking offshore wind farm as an example,this paper introduces a new method of establishing six evaluation indicators to determine the risk level according to the new technology and compliance principle of regional lightning protection(semi-circular method),which can be used for reference by wind farm technicians.展开更多
According to structure function and lightning damage of a cable car, a feasible method of lightning strike risk evaluation for a cable car was put forward based on the evaluation model and evaluation method in the sta...According to structure function and lightning damage of a cable car, a feasible method of lightning strike risk evaluation for a cable car was put forward based on the evaluation model and evaluation method in the standard IEC62305-2. According to the difference between common buildings and cable cars, problems of height non-uniformity of equivalent section caused by inclination of the cable car and diversity of lightning activity regularity caused by the large area were resolved, and expected annual average frequency of lightning strike was calculated using three dimensional graphic approach and regional lightning characteristic analysis. Based on different types of damage process and loss consequences, according to interception effect against lightning invasion of the lightning protection measures and the method of probability selection proposed in the standard, the probability of casu- alty caused by direct lightning strike in a cable car and a waiting area as well as probabilities of casualty caused by failure of electronic information systems were cal- culated.展开更多
Aircrafts damages caused by lightning strikes have been known since the early days of aviation.However,the physical effects on the aircraft structure are still being investigated.This work seeks to evaluate the lightn...Aircrafts damages caused by lightning strikes have been known since the early days of aviation.However,the physical effects on the aircraft structure are still being investigated.This work seeks to evaluate the lightning strike effects in the aluminum alloy 7075-T6.Samples were submitted to lightning strike simulation in laboratory and the damages evaluated through characterization techniques.Ultrasound and profilometry tests have shown material loss to 0.272 mm depth in the damaged region.In addition,it was detected the material accumulation occurrence in the damage vicinity of the region.Below the damage,it was found a region where metallurgical changes were identified.The tensile and microhardness tests results have shown reduction in the percentage elongation and hardness increasing in the material affected by lightning.These results are corroborated by the X-Ray Diffraction(XRD)and Rietveld Method(red line)that indicated an increasing in dislocation density and micro-deformation in the material matrix.Optical microscopy results have shown the presence of microcracks on the normal and cross-section surface of the samples damaged.The Energy Dispersive X-Ray Spectroscopy(EDXS)and Electron Backscattered Diffraction Test(EBSD)found coarse intermetallic phases and precipitates compounds with dimensions greater than 1 lm in length.They were responsible for nucleation of the microcracks that propagate along the material grain boundaries.展开更多
This article presents a mathematical model for simulating the mechanical behaviour of lightning strikes and analysing the resulting damage to the soil.This article focuses on the electro-thermal effect and seepage cau...This article presents a mathematical model for simulating the mechanical behaviour of lightning strikes and analysing the resulting damage to the soil.This article focuses on the electro-thermal effect and seepage caused by lightning strikes in particular.Then,a numerical model based on the conservation laws of momentum,mass and energy is developed for soil subjected to lightning strikes.Comparisons to field observations and theoretical calculations are used to demonstrate the efficacy and accuracy of numerical simulations.The findings demonstrate that lightning strikes can cause soils to experience both seepage force and heat stress.Under the calculative condition of this article:by increasing the intrinsic permeability of the soil,k_(p)(≥10^(-10)m^(2)),the seepage force can be effectively reduced,hence reducing the risk of lightning strikes;improving the electrical conductivity of the soil β(≥10^(-1) S/m^(2))and lowering its thermal expansion coefficient(≤10^(-6)K^(-1))can greatly reduce the damage caused by lightning strikes to the soil.The preceding investigations demonstrate that the suggested model is capable of evaluating mechanical damage caused by lightning in the soil,and the findings contribute to a better understanding of soil mechanical response to lightning strikes.展开更多
From July 31 to August I in 2008, a strong thunderstorm process occurred in Neijiang of Sichuan Province, and a strange scattered light- ning strike phenomenon happened in office building of Dongxing Meteorological Bu...From July 31 to August I in 2008, a strong thunderstorm process occurred in Neijiang of Sichuan Province, and a strange scattered light- ning strike phenomenon happened in office building of Dongxing Meteorological Bureau in Neijiang. Through a series of investigations and analyses, we found occurrence reason of the scattered lightning strike and improved lightning protection measures.展开更多
Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invent...Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invented the lightning rod in 1752,lightning rods have been used worldwide to prevent direct lightning strikes in various fields such as high-voltage power transmission lines,outdoor chemical sites,highways,land and sea wind farms,and forest lightning fire protection.It has been proven that lightning accidents still occur frequently in places where lightning rods are installed and the protective angle method is used.In order to further study the protective effect of lightning rods and identify the shortcomings of lightning rod protection,negative lightning strikes are taken as the research object,to analyze the limitations of lightning rods in preventing direct lightning strikes from the working principle of lightning rods.展开更多
A lightning strike accident of a residential house in the rural areas of Neijiang is analyzed through on-site investigation,and the causes are discussed. Defensive measures of lightning disasters are proposed to provi...A lightning strike accident of a residential house in the rural areas of Neijiang is analyzed through on-site investigation,and the causes are discussed. Defensive measures of lightning disasters are proposed to provide reference for the prevention of lightning disasters in the construction of new countryside.展开更多
A kind of interlaminar film with carbon nanotubes inserted into polyether ketone with cardo was used for lightning strike protection of composite laminates. The distribution of the interlaminar film was investigated b...A kind of interlaminar film with carbon nanotubes inserted into polyether ketone with cardo was used for lightning strike protection of composite laminates. The distribution of the interlaminar film was investigated by experimental and numerical methods. Artificial lightning strike tests were conducted for 12-film carbon nanotube and traditional surface silver coating protected specimens. Then corresponding finite element models(FEMs) were established to analyze the lightning strike effect and validated by the experimental results. Based on the FEMs, the number, distribution and thickness of interlaminar film were investigated in order to obtain equivalent protection effect with the traditional surface silver coating. The results show that only the first two layers were damaged for the surface silver coating protected specimen, while 5 layers were ablated for the 12-film protected specimen. Lightning strike damage area of the laminate protected with 5-film carbon nanotube is almost the same as that of the laminate protected with 12-film carbon nanotube. Compared with traditional surface silver coating protection, one film protection with thickness of 360 lm can make the laminate to obtain equivalent damage depth, 54.8% smaller damage area and 58% less additional weight. And reparability of the laminate is better than that of the laminate protected with 5 interlaminar films.展开更多
Traditional lightning protection measures can not solve the problem of superimposed lightning strikes.This paper presents a compressing arc extinguishing lightning protection device,which can solve the problem of supe...Traditional lightning protection measures can not solve the problem of superimposed lightning strikes.This paper presents a compressing arc extinguishing lightning protection device,which can solve the problem of superimposed lightning strikes.This device can extinguish the power frequency continuous current arc quickly in 1-2 ms.It is far less than the response time of relay protection,which can avoid lightning trips and improve the reliability of power supply.The computer simulation and engineering practice show that the compressing arc extinguishing device has good protection effect on superimposed lightning strikes.展开更多
The communication stations are more easily struck by lightning because of its special geographical position. We proved theoretically that communication station increased the frequency and intensity of lightning strike...The communication stations are more easily struck by lightning because of its special geographical position. We proved theoretically that communication station increased the frequency and intensity of lightning strike in its neighboring region, thereby causing the increasing of lightning disaster loss. As long as the emphasis is put on the correct understanding and reasonably taking measures including： draining, grounding, equipo- tential bonding and shielding, it can be completely ensured that building and equipment of communication base station and its neighboring region are safe.展开更多
In the past,lightning strike risk assessment of buildings mainly referred to the Protection against Lightning—Part 2:Risk Management(IEC 62305-2-2010)based on protection angle method.Lightning strike risk assessment ...In the past,lightning strike risk assessment of buildings mainly referred to the Protection against Lightning—Part 2:Risk Management(IEC 62305-2-2010)based on protection angle method.Lightning strike risk assessment of wind farms was conducted according to the Lightning Protection for Wind Energy System(IEC 61400-24-2019),which proposed the method of lightning strike risk assessment for wind turbine.In fact,the basic idea of the two is the same,that is,the source of the lightning strike wind turbine is transformed from the former S1-S4 to the latter N D-N DJ.According to the above method,wind farm was evaluated,and it has been proved that the practice can not achieve good results.After 2018,China has issued the Guide to Evaluation of Lightning Protection Technology in Buildings(T/GZLY 3-2022)and the Technical Specifications for Lightning Interception in Forest Areas(T/LYCY 4062-2024)based on semicircle protection,in which the source of risk defined by lightning point was closer to the reality,highly targeted and effective.Taking offshore wind farm as an example,this paper introduced a new method of establishing six evaluation indicators to determine the risk level according to the principle of compliance and the new protection technology of semi-circular method,which can be used as a reference for technical personnel.展开更多
The non-metallic lightning strike protection film covering carbon fiber reinforced polymers(NM-LSP covering CFRP)can reduce the weight and thus the fuel consumption of aircraft by replacing the traditional lightning s...The non-metallic lightning strike protection film covering carbon fiber reinforced polymers(NM-LSP covering CFRP)can reduce the weight and thus the fuel consumption of aircraft by replacing the traditional lightning strike protection(LSP)materials.In the present study,in order to study the environmental influence of utilizing NM-LSP covering CFRP in an aircraft elevator,a new elevator was designed and manufactured,replacing the aluminium net and glass fiber reinforced polymers(GFRP)with NM-LSP covering CFRP,with the same mechanical and LSP abilities.A comparative life cycle assessment was conducted between the two kinds of aircraft elevators,including material extraction,transportation,elevator manufacturing phase,service phase,and end-of-life procedures.Additionally,the environmental impacts of producing two LSP materials were compared by considering the environmental effects of different buy-to-fly ratios and recycling strategies on the production of aluminium net.The analysis indicates that the new elevator achieved reduction for all the environmental impact categories used,such as human toxicity potential and marine aquatic ecotoxicity potential(3.83%and 3.20%reduction).Furthermore,it is found that the service phase makes the greatest contribution to the environmental impact of the elevators under investigation.When recycling is excluded,NM-LSP covering CFRP is more environmentally friendly than the traditional material.At the same time,CFRP prepreg and electricity from the production of NM-LSP covering CFRP contribute to a higher environmental impact compared to the NM-LSP film.From the sensitivity analysis,it is believed that NM-LSP covering CFRP can reduce environmental impact compared with traditional LSP materials.展开更多
Three-dimensional finite element(FE)models of carbon/epoxy composite laminates with copper mesh and aluminum mesh protection were established subjected to lightning strike,in which different mesh spacing was selected....Three-dimensional finite element(FE)models of carbon/epoxy composite laminates with copper mesh and aluminum mesh protection were established subjected to lightning strike,in which different mesh spacing was selected.Effectiveness of numerical method was verified and impulse current waveforms with different current peaks were applied according to aircraft lightning zones.Thermal-electrical material parameters varying with temperature were added into numerical models.Element deletion method was used to deal with lightning ablation elements of composite structures.The results show that ablation area and depth of composite laminates with metal mesh protection are significantly smaller,which proves good protection effectiveness of metal meshes on anti-lightning strike.The denser the mesh spacing,the better the anti-lightning strike will be.Protection of composite laminates with copper mesh has better effects than that of aluminum mesh.Considering the effect of mesh spacing variation on composite structural weight and anti-lightning strike,the ideal mesh spacing was obtained.展开更多
Electric towers of high voltage transmission lines are more exposed to natural lightning phenomena thanks to their high heights. These lines are crossed by powerful current sources to dissipate in the ground, which ca...Electric towers of high voltage transmission lines are more exposed to natural lightning phenomena thanks to their high heights. These lines are crossed by powerful current sources to dissipate in the ground, which can, at one time or another, create disturbances or other phenomena can be generated. This is why we have set ourselves the objective of studying the FDTD modeling of the influence of direct lightning strikes on the power transmitted by a High-Voltage power line. To do this, we have implemented Kirchhoff’s laws to model the power transmitted by a High-Voltage power line in a steady state. Calculating the electromagnetic field generated by lightning requires the lightning current along the channel and its spatiotemporal distribution, the bi-exponential models and that of engineers were chosen and used to reproduce the physical phenomena best. Several works have been published in the literature and various mathematical models are proposed, to study the filamentous nature of power lines which has led to a more flexible modelling, based on the transmission line model, associated with the field theory developed from Maxwell’s equations, which explain the interaction between a lightning wave and a power transmission line. The resolution of the line equations in the lightning shock regime was the subject of the FDTD method to obtain the results in the spatio-temporal domain. Through this research, we are interested in the study of the spatiotemporal distribution of the lightning current wave to model the radiated electromagnetic field and to examine the influence of the overvoltage induced by the atmospheric discharge on the transportable power of a High Voltage AC Transmission line, for good selective protection to illuminate the parasites. 2D simulations based on proposed models were developed as well as the verification of the consistency of the different models, by comparing the fractal dimensions of the results of our program with those of the figures obtained experimentally. The aspects developed in this article could have direct implications in practical applications in the engineering and design of high-voltage transmission systems.展开更多
Lightning is a natural phenomenon with extremely high occurrence probability. This kind of natural phenomenon not only comes quickly, but also has extremely strong destructive power. It can form strong physical effect...Lightning is a natural phenomenon with extremely high occurrence probability. This kind of natural phenomenon not only comes quickly, but also has extremely strong destructive power. It can form strong physical effects such as shock wave and electromagnetic radiation in a short time, and affect buildings, electronic instruments and equipment. It is called one of the ten major natural disasters. During the operation of railway traction power supply catenary system, accidents such as equipment damage and train interruption caused by lightning strike often occur. Lightning protection technology can effectively protect the catenary system from insulator damage and line trip caused by lightning strikes. Through the research on lightning protection technology of OCS, the lightning protection countermeasures are explored to improve the reliability of line operation and ensure the safe operation of OCS equipment.展开更多
Generally speaking, the MW radio transmitting station will be located at a place with a relatively high altitude, which is relatively empty and has no other special buildings to cover the geographical position. In thi...Generally speaking, the MW radio transmitting station will be located at a place with a relatively high altitude, which is relatively empty and has no other special buildings to cover the geographical position. In this geographical position, although it is said that it is helpful for the signal to spread in a wider range, it will face a great risk of lightning strike if it is affected by thunderstorm weather. Once the medium wave radio transmitting station is struck by lightning, its facilities will not only be harmed, but also directly affect the normal broadcasting of the program, and even more serious will cause serious economic losses. Therefore, it is even more important to improve the lightning protection technology of the MW radio transmitting station. It is even more important to briefly summarize the lightning protection technology of the MW radio transmitting station. In order to deepen the technical level of lightning protection of the medium wave broadcasting transmitting station, a relative basis is given.展开更多
It is one of the most effective ways to use laboratory long air gap discharges for investigating the fundamental process involved in the lightning strike.During the 1960s and the 1970s,the electro-geometrical method(E...It is one of the most effective ways to use laboratory long air gap discharges for investigating the fundamental process involved in the lightning strike.During the 1960s and the 1970s,the electro-geometrical method(EGM)and the rolling sphere method were developed base on the breakdowncharacteristics of negative long spark discharges,which have been widely used to design the lightning shielding system of transmission lines and structures.In recent years,the scale of the power facilities is increased dramatically with the rising of power grid's voltage level.The impact of upward connecting leader launched from those large-scale facilities on the lightning shielding performance cannot be neglected;otherwise,the validity of the EGM in the lightning shielding design of EHV and UHV transmission lines will be challenged.The research evolutions on the lightning striking distance,the lightning simulation experiments and the positive upward connecting leader process by using laboratory long sparks are reviewed and discussed in this paper.展开更多
A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester ...A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester installed to the transformer,when a lightning strike happens,it may receive a very high lightning overvoltage,which is certainly resulted in the transformer damage at its insulation.Usually,a lightning arrester specification data attached to a lightning arrester contains the rating data of the lightning arrester current and voltage.In the use of lightning arrester,the possibility of receiving multiple lightning strikes is not taken into account sometimes.In fact,in some places,the number of multiple strikes in short duration is quiet high in number.This condition makes the lightning arrester being stroked by multiple lightning strikes.Therefore,it may change the lightning arrester's properties,and then the arrester may not be able to provide good electrical equipment protection against lightning strike anymore.This condition will result in great loss to electrical companies and electrical consumers.Therefore,this research studied the effect of applying multiple lightning strikes to ZnO lightning arrester block.Every time a group of lightning impulse current is applied to the ZnO lightning arrester block,it is followed by the measuring of its 50 Hz voltage and current characteristic. The changing in the ZnO lightning arrester block 50 Hz characteristic then can be analyzed.It was found that by applying more numbers of lightning strikes which made the arrester becoming worse,even though,actually,the lightning impulse peak current was still under the rating of the lightning arrester current.In this case for a 5 kA,24 kV lightning arrester,even though the lightning impulse peak current flowing through the ZnO lightning arrester block was still 2500 A,the lightning arrester ZnO block had already been damaged.Having been damaged,an alternating current flowing through the damaged ZnO block was about 10000 times as much current flowing to the good one.The maximum of impulse energy absorbed by a ZnO block recorded was 334.7 J/cm^3.The damaged ZnO block should be replaced by a good one.展开更多
A back-propagation neural network （BPNN） was used to establish relationships between the shortrange （0-3-h） rainfall and the predictors ranging from extrapolative forecasts of radar reflectivity, satelliteestimate...A back-propagation neural network （BPNN） was used to establish relationships between the shortrange （0-3-h） rainfall and the predictors ranging from extrapolative forecasts of radar reflectivity, satelliteestimated cloud-top temperature, lightning strike rates, and Nested Grid Model （NGM） outputs. Quan- titative precipitation forecasts （QPF） and the probabilities of categorical precipitation were obtained. Results of the BPNN algorithm were compared to the results obtained from the multiple linear regression algorithm for an independent dataset from the 1999 warm season over the continental United States. A sample forecast was made over the southeastern United States. Results showed that the BPNN categorical rainfall forecasts agreed well with Stage Ⅲ observations in terms of the size and shape of the area of rainfall. The BPNN tended to over-forecast the spatial extent of heavier rainfall amounts, but the positioning of the areas with rainfall ≥25.4 mm was still generally accurate. It appeared that the BPNN and linear regression approaches produce forecasts of very similar quality, although in some respects BPNN slightly outperformed the regression.展开更多
For several lightning-strike disasters related to base station iron tower of mobile communication carrier operator, disaster-inducing factors were analyzed. The reason was as below： after lightning receptor of base s...For several lightning-strike disasters related to base station iron tower of mobile communication carrier operator, disaster-inducing factors were analyzed. The reason was as below： after lightning receptor of base station iron tower of mobile communication carder operator was struck by lightning, electromagnetic radiation was generated in the process lightning current leaking into the ground. In addition, it was lightning scattered- strike phenomenon induced by overhead lightning rod, that is, ground lightning falling density around overhead lightning rod was larger than mean at the site. Finally, some improvement measures were put forward.展开更多
基金Supported by Research on Key Technologies of Lightning Intelligent Protection System for Guangdong Energy Hehe Sea Wind Farm(SFC/QZW-ZX-XF-24-020).
文摘In the past,the lightning strike risk assessment of wind farms mainly referred to the Lightning Protection Part 2:Risk Management(IEC 62305-2-2010)and the Lightning Protection of Wind Energy System(IEC 61400-24-2019)based on protection angle method.In fact,the basic idea of the two is the same,that is,the source of the lightning fan is replaced by S1-S4 of the former lightning building with the latter ND-NDJ.According to the above method of wind farm evaluation,it has been proved that the practice can not achieve good results.Taking offshore wind farm as an example,this paper introduces a new method of establishing six evaluation indicators to determine the risk level according to the new technology and compliance principle of regional lightning protection(semi-circular method),which can be used for reference by wind farm technicians.
基金Supported by the Scientific Research Project of Hebei Meteorological Bureau in 2014(14ky20)~~
文摘According to structure function and lightning damage of a cable car, a feasible method of lightning strike risk evaluation for a cable car was put forward based on the evaluation model and evaluation method in the standard IEC62305-2. According to the difference between common buildings and cable cars, problems of height non-uniformity of equivalent section caused by inclination of the cable car and diversity of lightning activity regularity caused by the large area were resolved, and expected annual average frequency of lightning strike was calculated using three dimensional graphic approach and regional lightning characteristic analysis. Based on different types of damage process and loss consequences, according to interception effect against lightning invasion of the lightning protection measures and the method of probability selection proposed in the standard, the probability of casu- alty caused by direct lightning strike in a cable car and a waiting area as well as probabilities of casualty caused by failure of electronic information systems were cal- culated.
文摘Aircrafts damages caused by lightning strikes have been known since the early days of aviation.However,the physical effects on the aircraft structure are still being investigated.This work seeks to evaluate the lightning strike effects in the aluminum alloy 7075-T6.Samples were submitted to lightning strike simulation in laboratory and the damages evaluated through characterization techniques.Ultrasound and profilometry tests have shown material loss to 0.272 mm depth in the damaged region.In addition,it was detected the material accumulation occurrence in the damage vicinity of the region.Below the damage,it was found a region where metallurgical changes were identified.The tensile and microhardness tests results have shown reduction in the percentage elongation and hardness increasing in the material affected by lightning.These results are corroborated by the X-Ray Diffraction(XRD)and Rietveld Method(red line)that indicated an increasing in dislocation density and micro-deformation in the material matrix.Optical microscopy results have shown the presence of microcracks on the normal and cross-section surface of the samples damaged.The Energy Dispersive X-Ray Spectroscopy(EDXS)and Electron Backscattered Diffraction Test(EBSD)found coarse intermetallic phases and precipitates compounds with dimensions greater than 1 lm in length.They were responsible for nucleation of the microcracks that propagate along the material grain boundaries.
基金funded by the Natural Science Foundation of China(Grant No.42077435)。
文摘This article presents a mathematical model for simulating the mechanical behaviour of lightning strikes and analysing the resulting damage to the soil.This article focuses on the electro-thermal effect and seepage caused by lightning strikes in particular.Then,a numerical model based on the conservation laws of momentum,mass and energy is developed for soil subjected to lightning strikes.Comparisons to field observations and theoretical calculations are used to demonstrate the efficacy and accuracy of numerical simulations.The findings demonstrate that lightning strikes can cause soils to experience both seepage force and heat stress.Under the calculative condition of this article:by increasing the intrinsic permeability of the soil,k_(p)(≥10^(-10)m^(2)),the seepage force can be effectively reduced,hence reducing the risk of lightning strikes;improving the electrical conductivity of the soil β(≥10^(-1) S/m^(2))and lowering its thermal expansion coefficient(≤10^(-6)K^(-1))can greatly reduce the damage caused by lightning strikes to the soil.The preceding investigations demonstrate that the suggested model is capable of evaluating mechanical damage caused by lightning in the soil,and the findings contribute to a better understanding of soil mechanical response to lightning strikes.
文摘From July 31 to August I in 2008, a strong thunderstorm process occurred in Neijiang of Sichuan Province, and a strange scattered light- ning strike phenomenon happened in office building of Dongxing Meteorological Bureau in Neijiang. Through a series of investigations and analyses, we found occurrence reason of the scattered lightning strike and improved lightning protection measures.
基金Supported by Lightning Multi-pulse Intelligent Monitoring System Optimization Technology Project of Guangdong Yuedian Dianbai Hot Water Wind Farm(SFC/DBW-Z-FW-23-006).
文摘Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invented the lightning rod in 1752,lightning rods have been used worldwide to prevent direct lightning strikes in various fields such as high-voltage power transmission lines,outdoor chemical sites,highways,land and sea wind farms,and forest lightning fire protection.It has been proven that lightning accidents still occur frequently in places where lightning rods are installed and the protective angle method is used.In order to further study the protective effect of lightning rods and identify the shortcomings of lightning rod protection,negative lightning strikes are taken as the research object,to analyze the limitations of lightning rods in preventing direct lightning strikes from the working principle of lightning rods.
文摘A lightning strike accident of a residential house in the rural areas of Neijiang is analyzed through on-site investigation,and the causes are discussed. Defensive measures of lightning disasters are proposed to provide reference for the prevention of lightning disasters in the construction of new countryside.
文摘A kind of interlaminar film with carbon nanotubes inserted into polyether ketone with cardo was used for lightning strike protection of composite laminates. The distribution of the interlaminar film was investigated by experimental and numerical methods. Artificial lightning strike tests were conducted for 12-film carbon nanotube and traditional surface silver coating protected specimens. Then corresponding finite element models(FEMs) were established to analyze the lightning strike effect and validated by the experimental results. Based on the FEMs, the number, distribution and thickness of interlaminar film were investigated in order to obtain equivalent protection effect with the traditional surface silver coating. The results show that only the first two layers were damaged for the surface silver coating protected specimen, while 5 layers were ablated for the 12-film protected specimen. Lightning strike damage area of the laminate protected with 5-film carbon nanotube is almost the same as that of the laminate protected with 12-film carbon nanotube. Compared with traditional surface silver coating protection, one film protection with thickness of 360 lm can make the laminate to obtain equivalent damage depth, 54.8% smaller damage area and 58% less additional weight. And reparability of the laminate is better than that of the laminate protected with 5 interlaminar films.
基金the National Natural Science Foundation of China(No.51467002)Special Projects for Innovation-driven Development(No.2018AA03001Y).
文摘Traditional lightning protection measures can not solve the problem of superimposed lightning strikes.This paper presents a compressing arc extinguishing lightning protection device,which can solve the problem of superimposed lightning strikes.This device can extinguish the power frequency continuous current arc quickly in 1-2 ms.It is far less than the response time of relay protection,which can avoid lightning trips and improve the reliability of power supply.The computer simulation and engineering practice show that the compressing arc extinguishing device has good protection effect on superimposed lightning strikes.
文摘The communication stations are more easily struck by lightning because of its special geographical position. We proved theoretically that communication station increased the frequency and intensity of lightning strike in its neighboring region, thereby causing the increasing of lightning disaster loss. As long as the emphasis is put on the correct understanding and reasonably taking measures including： draining, grounding, equipo- tential bonding and shielding, it can be completely ensured that building and equipment of communication base station and its neighboring region are safe.
基金Huadian International Group Technology Project(172JLC02300248)Research Project on Lightning Protection Technology for 35 kV Collecting Power Line of Wuxuan Qinglan Wind Farm(SFC/WXY-ZX-FW-23-008).
文摘In the past,lightning strike risk assessment of buildings mainly referred to the Protection against Lightning—Part 2:Risk Management(IEC 62305-2-2010)based on protection angle method.Lightning strike risk assessment of wind farms was conducted according to the Lightning Protection for Wind Energy System(IEC 61400-24-2019),which proposed the method of lightning strike risk assessment for wind turbine.In fact,the basic idea of the two is the same,that is,the source of the lightning strike wind turbine is transformed from the former S1-S4 to the latter N D-N DJ.According to the above method,wind farm was evaluated,and it has been proved that the practice can not achieve good results.After 2018,China has issued the Guide to Evaluation of Lightning Protection Technology in Buildings(T/GZLY 3-2022)and the Technical Specifications for Lightning Interception in Forest Areas(T/LYCY 4062-2024)based on semicircle protection,in which the source of risk defined by lightning point was closer to the reality,highly targeted and effective.Taking offshore wind farm as an example,this paper introduced a new method of establishing six evaluation indicators to determine the risk level according to the principle of compliance and the new protection technology of semi-circular method,which can be used as a reference for technical personnel.
基金supported by the National Key Research and Development Program of China(No.2017YFC0703007)the Chinese MIIT Special Research Plan on Civil Aircraft(No.MJ-2015-H-G-103)+1 种基金the National Natural Science Foundation of China(No.52008137)the China Postdoctoral Science Foundation(Nos.2019TQ0079 and 2019M661288)。
文摘The non-metallic lightning strike protection film covering carbon fiber reinforced polymers(NM-LSP covering CFRP)can reduce the weight and thus the fuel consumption of aircraft by replacing the traditional lightning strike protection(LSP)materials.In the present study,in order to study the environmental influence of utilizing NM-LSP covering CFRP in an aircraft elevator,a new elevator was designed and manufactured,replacing the aluminium net and glass fiber reinforced polymers(GFRP)with NM-LSP covering CFRP,with the same mechanical and LSP abilities.A comparative life cycle assessment was conducted between the two kinds of aircraft elevators,including material extraction,transportation,elevator manufacturing phase,service phase,and end-of-life procedures.Additionally,the environmental impacts of producing two LSP materials were compared by considering the environmental effects of different buy-to-fly ratios and recycling strategies on the production of aluminium net.The analysis indicates that the new elevator achieved reduction for all the environmental impact categories used,such as human toxicity potential and marine aquatic ecotoxicity potential(3.83%and 3.20%reduction).Furthermore,it is found that the service phase makes the greatest contribution to the environmental impact of the elevators under investigation.When recycling is excluded,NM-LSP covering CFRP is more environmentally friendly than the traditional material.At the same time,CFRP prepreg and electricity from the production of NM-LSP covering CFRP contribute to a higher environmental impact compared to the NM-LSP film.From the sensitivity analysis,it is believed that NM-LSP covering CFRP can reduce environmental impact compared with traditional LSP materials.
基金supported financially by the National Natural Science Foundation of China (No.51875463)the Natural Science Basic Research Plan in Shaanxi Province of China (No.2018JM1001)the Seed Foundation of Innovation and Creation for Graduate Students in Northwestern Polytechnical University (No.ZZ2018107)
文摘Three-dimensional finite element(FE)models of carbon/epoxy composite laminates with copper mesh and aluminum mesh protection were established subjected to lightning strike,in which different mesh spacing was selected.Effectiveness of numerical method was verified and impulse current waveforms with different current peaks were applied according to aircraft lightning zones.Thermal-electrical material parameters varying with temperature were added into numerical models.Element deletion method was used to deal with lightning ablation elements of composite structures.The results show that ablation area and depth of composite laminates with metal mesh protection are significantly smaller,which proves good protection effectiveness of metal meshes on anti-lightning strike.The denser the mesh spacing,the better the anti-lightning strike will be.Protection of composite laminates with copper mesh has better effects than that of aluminum mesh.Considering the effect of mesh spacing variation on composite structural weight and anti-lightning strike,the ideal mesh spacing was obtained.
文摘Electric towers of high voltage transmission lines are more exposed to natural lightning phenomena thanks to their high heights. These lines are crossed by powerful current sources to dissipate in the ground, which can, at one time or another, create disturbances or other phenomena can be generated. This is why we have set ourselves the objective of studying the FDTD modeling of the influence of direct lightning strikes on the power transmitted by a High-Voltage power line. To do this, we have implemented Kirchhoff’s laws to model the power transmitted by a High-Voltage power line in a steady state. Calculating the electromagnetic field generated by lightning requires the lightning current along the channel and its spatiotemporal distribution, the bi-exponential models and that of engineers were chosen and used to reproduce the physical phenomena best. Several works have been published in the literature and various mathematical models are proposed, to study the filamentous nature of power lines which has led to a more flexible modelling, based on the transmission line model, associated with the field theory developed from Maxwell’s equations, which explain the interaction between a lightning wave and a power transmission line. The resolution of the line equations in the lightning shock regime was the subject of the FDTD method to obtain the results in the spatio-temporal domain. Through this research, we are interested in the study of the spatiotemporal distribution of the lightning current wave to model the radiated electromagnetic field and to examine the influence of the overvoltage induced by the atmospheric discharge on the transportable power of a High Voltage AC Transmission line, for good selective protection to illuminate the parasites. 2D simulations based on proposed models were developed as well as the verification of the consistency of the different models, by comparing the fractal dimensions of the results of our program with those of the figures obtained experimentally. The aspects developed in this article could have direct implications in practical applications in the engineering and design of high-voltage transmission systems.
文摘Lightning is a natural phenomenon with extremely high occurrence probability. This kind of natural phenomenon not only comes quickly, but also has extremely strong destructive power. It can form strong physical effects such as shock wave and electromagnetic radiation in a short time, and affect buildings, electronic instruments and equipment. It is called one of the ten major natural disasters. During the operation of railway traction power supply catenary system, accidents such as equipment damage and train interruption caused by lightning strike often occur. Lightning protection technology can effectively protect the catenary system from insulator damage and line trip caused by lightning strikes. Through the research on lightning protection technology of OCS, the lightning protection countermeasures are explored to improve the reliability of line operation and ensure the safe operation of OCS equipment.
文摘Generally speaking, the MW radio transmitting station will be located at a place with a relatively high altitude, which is relatively empty and has no other special buildings to cover the geographical position. In this geographical position, although it is said that it is helpful for the signal to spread in a wider range, it will face a great risk of lightning strike if it is affected by thunderstorm weather. Once the medium wave radio transmitting station is struck by lightning, its facilities will not only be harmed, but also directly affect the normal broadcasting of the program, and even more serious will cause serious economic losses. Therefore, it is even more important to improve the lightning protection technology of the MW radio transmitting station. It is even more important to briefly summarize the lightning protection technology of the MW radio transmitting station. In order to deepen the technical level of lightning protection of the medium wave broadcasting transmitting station, a relative basis is given.
文摘It is one of the most effective ways to use laboratory long air gap discharges for investigating the fundamental process involved in the lightning strike.During the 1960s and the 1970s,the electro-geometrical method(EGM)and the rolling sphere method were developed base on the breakdowncharacteristics of negative long spark discharges,which have been widely used to design the lightning shielding system of transmission lines and structures.In recent years,the scale of the power facilities is increased dramatically with the rising of power grid's voltage level.The impact of upward connecting leader launched from those large-scale facilities on the lightning shielding performance cannot be neglected;otherwise,the validity of the EGM in the lightning shielding design of EHV and UHV transmission lines will be challenged.The research evolutions on the lightning striking distance,the lightning simulation experiments and the positive upward connecting leader process by using laboratory long sparks are reviewed and discussed in this paper.
文摘A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester installed to the transformer,when a lightning strike happens,it may receive a very high lightning overvoltage,which is certainly resulted in the transformer damage at its insulation.Usually,a lightning arrester specification data attached to a lightning arrester contains the rating data of the lightning arrester current and voltage.In the use of lightning arrester,the possibility of receiving multiple lightning strikes is not taken into account sometimes.In fact,in some places,the number of multiple strikes in short duration is quiet high in number.This condition makes the lightning arrester being stroked by multiple lightning strikes.Therefore,it may change the lightning arrester's properties,and then the arrester may not be able to provide good electrical equipment protection against lightning strike anymore.This condition will result in great loss to electrical companies and electrical consumers.Therefore,this research studied the effect of applying multiple lightning strikes to ZnO lightning arrester block.Every time a group of lightning impulse current is applied to the ZnO lightning arrester block,it is followed by the measuring of its 50 Hz voltage and current characteristic. The changing in the ZnO lightning arrester block 50 Hz characteristic then can be analyzed.It was found that by applying more numbers of lightning strikes which made the arrester becoming worse,even though,actually,the lightning impulse peak current was still under the rating of the lightning arrester current.In this case for a 5 kA,24 kV lightning arrester,even though the lightning impulse peak current flowing through the ZnO lightning arrester block was still 2500 A,the lightning arrester ZnO block had already been damaged.Having been damaged,an alternating current flowing through the damaged ZnO block was about 10000 times as much current flowing to the good one.The maximum of impulse energy absorbed by a ZnO block recorded was 334.7 J/cm^3.The damaged ZnO block should be replaced by a good one.
文摘A back-propagation neural network （BPNN） was used to establish relationships between the shortrange （0-3-h） rainfall and the predictors ranging from extrapolative forecasts of radar reflectivity, satelliteestimated cloud-top temperature, lightning strike rates, and Nested Grid Model （NGM） outputs. Quan- titative precipitation forecasts （QPF） and the probabilities of categorical precipitation were obtained. Results of the BPNN algorithm were compared to the results obtained from the multiple linear regression algorithm for an independent dataset from the 1999 warm season over the continental United States. A sample forecast was made over the southeastern United States. Results showed that the BPNN categorical rainfall forecasts agreed well with Stage Ⅲ observations in terms of the size and shape of the area of rainfall. The BPNN tended to over-forecast the spatial extent of heavier rainfall amounts, but the positioning of the areas with rainfall ≥25.4 mm was still generally accurate. It appeared that the BPNN and linear regression approaches produce forecasts of very similar quality, although in some respects BPNN slightly outperformed the regression.
文摘For several lightning-strike disasters related to base station iron tower of mobile communication carrier operator, disaster-inducing factors were analyzed. The reason was as below： after lightning receptor of base station iron tower of mobile communication carder operator was struck by lightning, electromagnetic radiation was generated in the process lightning current leaking into the ground. In addition, it was lightning scattered- strike phenomenon induced by overhead lightning rod, that is, ground lightning falling density around overhead lightning rod was larger than mean at the site. Finally, some improvement measures were put forward.
