Gotowa bibliografia na temat „Lightning strike rate”

Abstract According to field operation records, lightning stroke accounts for 60% of transmission line failures. Therefore, it is of great significance to strengthen lightning protection of the power system. However, there are several lightning faults, and the corresponding protection methods differ. Consequently, identifying lightning stroke faults will be beneficial to take corresponding lightning protection measures. This paper investigates the mechanism of different lightning strike faults, and simulates them by a 110kV transmission line EMTP-ATP model. Analysis and simulation show that the direction of tower current represents lightning’s polarity; the insulator voltage’s direction differs when shielding failure or back striking occurs. If insulator flashovers, the voltage of the insulator drops down to zero, and as the transient process comes to an end, the voltage of the insulator on the nearby tower decreases to zero as well; after the occurrence of back striking flashover, the direction of insulator voltage on nearby tower alters. Based on those features, insulator voltage and tower current are introduced as a characteristic signal, and their direction and rms of them are formed as recognition parameters for lightning stroke identification. The EMTP-ATP simulations demonstrate that the proposed method is correct and effective, and the recognition rate of different lightning faults is 100% under the abovementioned method.

Since the main way of power transmission in China is overhead line transmission, some overhead lines are in a harsh outdoor environment. Among them, the bypass attack is more serious. Shielding Failure is a severe form of lightning damage. Based on the situation, this article studies the lightning shielding phenomenon of transmission lines. This article uses the pilot development model to simulate the lightning strike process, analyzes the different target objects of the lightning strike, and elaborates and calculates the lightning shielding trip rate. In addition, by changing the protection angle, the height of the tower, the ground inclination of the area where the line is located, and the number of lines, the impact of these four factors on the lightning shielding trip rate is discussed. According to the influencing factors, measures to strengthen the lightning protection performance of the line are proposed.

It is difficult to monitor lightning damage to carbon fibre-reinforced polymers (CFRPs) online. This work experimentally investigates the changes associated with the electrical resistance of CFRPs subjected to lightning strikes. Two kinds of simulated lightning currents with different amplitudes in the range of 10–80 kA were injected into the CFRP samples. By measuring and comparing the changes in the struck-side (front) surface resistance, the surface resistance of the side opposite to the struck-side (back) and the oblique resistance of each sample before and after the lightning strike, it was observed that inflection points exist in the curve of the resistance change rate. The resistance decreases with increasing peak currents before the inflection point and increases when the peak current goes beyond the inflection point. The change rate of the front surface resistance is more sensitive to the lightning damage than are those of the back surface resistance and the oblique resistance. Different simulated lightning currents have approximately the same action integrals at the inflection points of resistance change rate. The characteristics indicate that resistance change detection could be a possible method for the online monitoring of CFRP lightning damage.

Lightning is one of the leading causes of weather-related fatalities. A man, approximately 30 years old, was brought to the morgue of Kishoreganj District Hospital, Bangladesh, in July 2021, known to be lightning strike victim. During postmortem examination, various types of skin burns were found in the body, at an entry site on and near the head, and at an inferiorly located exit site. The skin injuries consisted of superficial burns, charring, and singed hair; however, there was no deep burn. „Lichtenberg figures‟ were found. Internal findings at autopsy were nonspecific. Epidemiologically, the total number of global annual lightning fatalities range from 6,000 to 24,000 per year. In recent years, Bangladesh experiences a high rate of lightning deaths. We feel that the number of deaths by lightning should be seen as a call to action. Hence, deaths by lightning should be regarded as a public health problem in the country and necessary measures must be taken. Our case study aims to draw the attention of the physicians and public health department on injuries and deaths due to lightning strike. It is also important for forensic professionals to be familiar with the nature of injuries caused by lightning and lightning strike deaths. CBMJ 2022 January: vol. 11 no. 01 P: 52-55

This paper evaluates the effect of a lightning strike directly on the 24 kV distribution lines in Thailand, where such strikes are one of the main causes of power outages. The voltage across the insulator, and the arrester energy absorbed due to the lightning, need to be analyzed for different grounding distances of the overhead ground wire, ground resistance, lightning impact positions, and lightning current waveforms. Analysis and simulations are conducted using the Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) to find the energy absorbed by the arrester and the voltages across the insulator. The results indicate that when surge arresters are not installed, the voltage across the insulator at the end of the line is approximately 1.4 times that in the middle of the line. In addition, the ground resistance and grounding distance of the overhead ground wire affect the voltage across the insulator if the overhead ground wire is struck. When surge arresters are installed, a shorter grounding distance of the overhead ground wire and a lower ground resistance are not always desirable; this is because they reduce the back-flashover rate and the voltage across the insulator if lightning strikes the overhead ground wire. However, lightning strikes to the phase conductor result in high arrester energy and the possibility that the arrester will fail. Furthermore, the tail time of the lightning waveform is a significant variable when considering the energy absorbed by the arrester, whereas the front time is important for the voltage across the insulator. In case lightning strikes directly on the connected point between the overhead lines and the underground cables, the distribution line system is protected only by the lightning arrester at the connection point. The overvoltage at the connection point is lower than the basic impulse level at 24 kV of 125 kV, but the overvoltage at the end of the cable is still more than 125 kV in case the cable is longer than 400 m. When the distribution line system is protected by the lightning arrester at both the connection point and the end of the cable, it results in overvoltage throughout the cable is lower than the critical flashover of insulation. This method is the best way to reduce the failure rate of underground cables and equipment that are connected to the distribution line system.

Egineering running experience shows that with the increase of the operating voltage of the transmission line, the lightning trip rate is increasing. According to theoretical calculation ， UHV transmission lines should be provided with full lightning protection characteristics；however，running experience shows that the lightning withstand level of UHV transmission lines is high，not completely lightning protection; it puts forward higher requirements for lightning protection design of UHV transmission line in China. UHV transmission line is mainly against direct lightning stroke characteristics， one is caused by lightning counterattack trip，the other is the shielding failure of lightning around the line to strike the wound caused by the wire. The lightning fault type identification is based on the micro topography of UHV transmission tower，accumulation of historical data，the development of a more targeted and high voltage transmission line lightning protection scheme is of great significance. In this paper, a real-time identification system based on UV detection technology, which has high accuracy and fast response time, is proposed for lightning fault types of UHV transmission lines, the systems use ultraviolet light to realize online detection of high-voltage transmission line tower nearby lightning, can effective observation tower near lightning discharge, and it has the characteristics of continuous detection, longdistance, no power supply, no contact and no disassembly, it provides an advanced technology for the detection of lightning discharge in UHV transmission line.

Lightning can be defined as a transient, high-current (typically tens of kA) electric discharge in air whose length is measured in km. As for any discharge in air, lightning channel is composed of ionized gas, that is, of plasma, whose peak temperature is typically 30,000 K, about five times higher than the temperature of the surface of the Sun. The global lightning flash rate is some tens to a hundred km per second. Lightning initiates many forest fires, and over 30% of all electric power line failures are lightning related. Each commercial aircraft is struck by lightning on average once a year. A lightning strike to an unprotected object or system can be catastrophic. In the first part [1] of the article, an overview of thunderclouds and their charge structure was given, and different types of lightning were described. The existing hypotheses of lightning initiation in thunderclouds were reviewed. In the second part of the article, current and electromagnetic signatures of lightning are characterized and the techniques to measure lightning electric and magnetic fields are discussed

AbstractThis paper proposes a progressive damage model incorporating strain and heating rate effects for the prediction of composite specimen damage resulting from simulated lightning strike test conditions. A mature and robust customised failure model has been developed. The method used a scaling factor approach and non-linear degradation models from published works to modify the material moduli, strength and stiffness properties to reflect the effects of combined strain and thermal loading. Hashin/Puck failure criteria was used prior to progressive damage modelling of the material. Each component of the method was benchmarked against appropriate literature. A three stage modelling framework was demonstrated where an initial plasma model predicts specimen surface loads (electrical, thermal, pressure); a coupled thermal-electric model predicts specimen temperature resulting from the electrical load; and a third, dynamic, coupled temperature-displacement, explicit model predicts the material state due to the thermal load, the resulting thermal-expansion and the lightning plasma applied pressure loading. Unprotected specimen damage results were presented for two SAE lightning test Waveforms (B & A); with the results illustrating how thermal and mechanical damage behaviour varied with waveform duration and peak current.

The distribution and conduction path of lightning current inside carbon fiber-reinforced polymer (CFRP) composites subjected to lightning strikes are determined by their dynamic conductive characteristics. An experimental platform that generates lightning current impulses with variable parameters was established to obtain the equivalent conductivities of CFRPs with different laminated structures. The experimental results indicated that the through-thickness conductivity (10−3 S/mm) was much lower than the in-plane conductivity (100 S/mm). Then, the dynamic conduction model of CFRPs was analyzed based on the anisotropic nonlinear conductivities of CFRPs under lightning currents of 50–1000 A. The CFRP laminate could be regarded as a series circuit of resistance and inductance. The dynamic conductance of the CFRP laminate first increased and then decreased during the single lightning current strike process, which was closely related to the conductive properties of the interlaminar resin. The inductive properties of the CFRP material were manifested in the test results, which showed that the voltage reached the peak value prior to the current waveform and the equivalent conductivities of the CFRPs increased as the rate of increase decreased and the duration increased. In addition, the equivalent inductance of the carbon fiber network was found to be an important part of the inductive effect of CFRP laminates. This research is helpful for understanding the complicated relationships in the lightning current conducting process and can provide experimental and theoretical support for CFRP coupled electrical–thermal simulation studies of lightning direct effects.

Due to micro landforms and climate, the 110 kV transmission lines crossing the mountain areas are exposed to severe icing conditions for both their high voltage (HV) conductors and shield wires during the winter. Ice accumulation on the shield wire causes excessive sag, which leads to a reduced clearance between earth and HV wires, and could eventually result in tripping of the line due to phase-to-ground flashover. Due to the lack of effective de-icing techniques for the shield wires, removing them completely from the existing overhead line (OHL) structure becomes a reasonable solution to prevent icing accidents. Nevertheless, the risk of exposure to lightning strikes increased significantly after the shield wires were removed. In order to cope with this, the anti-thunder and anti-icing composite insulator (AACI) is installed on the OHLs. In this article, the 110 kV transmission line without shield wire is considered. The shielding failure after installation of the AACIs is studied using the lightning strike simulation models established in the ATP software. The lightning stroke flashover tests are carried out to examine the shielding failures on various designs for the AACIs. Assuming the tower’s earth resistance is 30 Ω, the LWL of back flashover and direct flashover are 630.88 kA and 261.33 kA, respectively, after the installation of AACIs on an unearthed OHL. Due to the unique mechanism of the AACI, the operational voltage level and the height of the pylon have a neglectable influence on its lightning withstand level (LWL). When the length of the parallel protective gap increases from 450 mm to 550 mm, the lightning trip-out rate decreases from 0.104 times/100 km·a to 0.014 times/100 km·a, and the drop rate reaches 86.5%. Therefore, increasing the gap distance for the AACI to provide additional clearance is proven to be an effective method to reduce the shielding failure rates for non-shield-wired OHLs.

Air transport plays a vital role in global economic growth and long-distance commutation. The aviation industry is found to double its fleet size every fifteen years. According to Air Transport Action Group (ATAG), 45 million aircraft took off worldwide in 2019, which translates to 1.5 lakh per day. Similar numbers are reported for other years under normal circumstances. Therefore, aviation appears to be an indispensable part of modern human civilization. Lightning is known to be one of the serious environmental threats to aircraft. Past incidents show that lightning strikes can lead to structural damage, operational interruption, and loss of lives. Field data suggest that, on average, an aircraft can get struck by lightning once or twice a year. Further, according to NOAA, The lightning strikes typically cost approximately two billion dollars to airline operators annually. Therefore, lightning protective measures are considered a crucial aspect of aircraft design. Design of suitable lightning protective measures involves Zoning of aircraft’s outer surface. Aircraft Zoning intends to differentiate lightning attachment points, channel slipping regions, and regions that carry just the stroke current. The first step in Zoning is to identify the initial attachment points. For the same, different methods like laboratory experiments, similarity principle, Rolling Sphere Method (RSM), and field-based approach are suggested in the standard, Aerospace Recommended Practice (ARP)-5414. Several aircraft accidents attributed to lightning strikes during the mid-20th century encouraged engineers to investigate the phenomena more closely. Therefore, several in-flight measurement campaigns were carried out in the late 80's, where the aircraft were flown inside the thunderstorm with the intention of getting struck by lightning. Field observation from these campaigns suggests two modes of lightning attachment, Aircraft-initiated and aircraft-intercepted. In the former one, under the influence of a thundercloud or descending lightning leader, the aircraft initiates bipolar leaders that lead to a strike. These leaders are deemed to propagate hundreds of meters to complete the lightning strike. In aircraft-intercepted strikes, the aircraft intercepts a descending lightning leader and hence gets struck. The methods suggested in the standard for identifying initial attachment points on aircraft are simple and have limitations. − The laboratory experiments on scaled aircraft models or isolated aircraft parts cannot portray all the aspects of discharges leading to the attachment. Therefore, the laboratory results cannot be directly extended to actual aircraft. − The similarity principle suggested in the standard is qualitative and can’t be extended to aircraft of any size and shape. − The field-based approach is not properly described in the standard, and hence, lacks clarity. − The 25 m Rolling Sphere Method (RSM) is routinely employed to determine the initial attachment points. Being a striking-distance-based approach, RSM only depicts the last stage of aircraft- intercepted attachment and, thus, doesn’t consider aircraft-initiated leaders. However, it is reported that 90% of the lightning strikes to aircraft are attributed to aircraft-initiated mode, which involves significant connecting leader activities. Therefore, precise assessment of initial attachment points requires considering the aircraft-initiated leader discharges. From the above discussion, it is evident that modeling bipolar leader discharges from aircraft is imperative in the context of lightning protection design. In literature, it is difficult to find a model for bipolar leader discharges from aircraft. However, works on either negative or positive leader discharge from energized electrodes in laboratory gaps and their extension to grounded objects are well-regarded in the literature. Knowledge from these works is found to be helpful to the present work. In spite of being responsible for most attachments, a model for bipolar leader discharges from aircraft is hard to find in the literature. Therefore, this work aims to develop a model for the inception and propagation of bipolar leaders from aircraft. Electrical discharges being field-driven phenomena, field computation is essential. Identifying the problem in hand as an open-geometry problem, a boundary-based method, Surface Charge Simulation Method (SCSM), is chosen for field computation. SCSM provides the global field distribution around the aircraft. Aircraft extremities are the most probable regions that can initiate discharges and, therefore, requires capturing the field around them in detail. The same is achieved by employing sub-modeling at the extremities. Sub-model charges are calculated using Charge Simulation Method (CSM), while the boundary condition on the sub-model is extracted from the global field solution. Modeling aircraft-initiated leader discharges involve modeling positive and negative leader discharges. Several models for positive and negative leader discharges in laboratory gaps are available in the literature. The latest model available in the literature for a positive leader discharge was developed by Becerra and Cooray. To reduce the computational burden, a simplified version of the model, which is also suggested by them, is considered in the present work. For negative leader discharge, a simplified physical model proposed by Z.Guo et al. is considered. Using the constructed model, the mechanism involved in the inception and propagation of the aircraft-initiated leader discharges is investigated and quantified. In contrast with discharges from energized electrodes or objects on the grounds, a few salient aspects of bipolar leader discharge from aircraft are pointed out. It is shown that aircraft potential changes with the development of connecting leaders, which modifies the field around it. As a consequence of the same, unipolar stable leader discharge from an aircraft is not viable. Therefore, the aircraft-initiated positive and negative leader discharges in a mutually supporting form are essential for the stable propagation of connecting leaders. The minimum ambient fields required for the stable propagation of bipolar leaders from a medium (DC-10) and a small aircraft (SDM) are determined. The values are well within the fields measured during different measurement campaigns. Subsequently, the dependency of this threshold field on permissible pitch and roll angle, aircraft flying altitude, and humidity are quantified. The aircraft-intercepted lightning strikes are also accounted for in this work. It is shown that, being electrically floating, the magnitude of aircraft potential increases, keeping the polarity the same as the descending leader tip potential. However, it is not the case for objects on the ground (i.e., buildings, towers, etc.). Therefore, the striking-distance-based approach, routinely employed for designing lightning protection for grounded objects, cannot be directly extended to aircraft. This also indicates a possible limitation of RSM while applied on aircraft. Further, The critical stroke current below which aircraft-intercepted mode of attachment is most probable is determined for two aircraft models, DC-10 and SDM. Unlike structures on the ground, the weight and volume of the lightning protection for aircraft should be constrained. Therefore, to provide adequate protection, it is absolutely essential to quantify the probability of lightning strikes to aircraft. Thus, based on the above model for lightning attachment, this work develops a methodology for estimating the rate of lightning strikes to aircraft. This method takes aircraft dimensions and spatial densities of lightning flashes and thunderstorms along its route as input. The proposed method is employed to estimate the average annual number of strikes to aircraft worldwide. Subsequently, the dependency of the strike rate on aircraft size and flying altitude are investigated. The entire exercise is carried out for medium-sized (DC-10) and small (SDM) aircraft. The estimated strike rates are well within the range of reported field data. Further, the estimated variation of strike rates with altitudes (below 3 km) correlates well with the data published by Boeing. The small deviations observed in the estimated strike rates are attributed to the assumption of cloud heights and takeoff/landing trajectory. Therefore, given exact data on thunderstorms, lightning flashes, and the operational behavior of an aircraft, the methodology can reliably estimate the rate of lightning strikes to aircraft. In summary, this work has developed a model for the inception and propagation of bipolar leaders from aircraft and also correctly picturizes the direct streamer mode of bridging involved in aircraft-intercepted attachment. The role of the air density (hence, altitude) is incorporated in the model, along with selected humidity values. The proposed model provides a discharge-physics-based method of identifying initial attachment points on aircraft. Therefore, the limitations of the methods suggested in the standard are overcome.The work has also developed a methodology for estimating the strike rate as a function of altitude, aircraft size, thunderstorms, and lightning flash density. The estimated strike rates correlate well with the reported data from field observation.

Lightning strikes are rare accidents but carry a 10% case fatality, killing 0.1 to 0.3 per million population each year. During thunderstorms, the risk is increased by sheltering under trees or by being on open water, on tractors, or in open fields or golf courses....

This chapter traces the rise of antinuclear activism throughout 1980 and 1981, focusing on the proliferation of grassroots campaigns and massive rallies as the Cold War seemed to return to Europe in full force. It talks about the decision to host cruise missiles on the soil of the United Kingdom that would make the country a likely target for a limited Soviet preemptive strike. Concerned citizens flooded the streets to attend massive rallies and throw their weight behind an array of campaigns to stop NATO's deployments and halt the nuclear arms race. The chapter mentions the opposition to the Euromissiles that brought together people who had mobilized to ban the bomb, protested the Vietnam War, and picketed nuclear power plants. NATO's Dual-Track Decision served as both a lightning rod and a lowest common denominator around which a diverse group could rally.

Lightning strikes are rare accidents but carry a 10% case fatality, killing 0.1–0.3 per million population each year. During thunderstorms, the risk is increased by sheltering under trees or by being on open water, on tractors, or in open fields or in outdoor activity. Lightning is considered to cause instant asystole. Immediate cardiopulmonary resuscitation is mandatory. Survivors might develop complications including pain syndromes and psychological sequelae. Burns are generally of minor consequence, unlike electrical injury. The most disabling consequences of the injury is generally the psychological sequelae. Meanwhile, electrocution is the fifth most common cause of workplace death, mainly affecting utilities, mining, and construction labourers. Domestic electrical accidents are common, where contact with overhead power lines, faulty power tools, and particularly using extension cords, are the most common causes, with metal ladders and antennae being particularly dangerous.

Although environmental emergencies are not the most common presentations to the emergency department (ED), as humans continue to explore more remote areas of the planet and as large populations encounter environmental change at increasing rates, it is important for emergency clinicians to know how to manage these conditions. From extremes of temperature, to extremes of pressure, to drownings and lightning strikes, to a myriad of possible envenomations, environmental emergencies are interesting and diverse. This chapter presents questions related to the diagnosis, clinical effects, best first response in the ED, and most appropriate treatment of a wide range of these environmental emergencies.

Abstract Reliability of electronic drivers, or systems, is crucial for the business of Signify. We manufacture and sell more than a million drivers per year. Field returns taught us what failure modes are important, but this is not sufficient to provide lifetime claims for our products. Being in this business for almost a century, in order to provide detailed lifetime claims, we have established an internal reliability tool. This tool provides our designers the correct information for flawless driver development. The specially developed Electronics Reliability Tool (ERT) uses on the one hand FIT tables provided by handbooks like e.g., Telcordia and on the other hand also considers wear-out mechanisms due to e.g., lightning strikes. Validation and verification of our predictions is performed by collecting sold quantities, field returns, do extensive failure analysis and compare these values with calculated ones. Each internally designed driver is subjected to an ERT calculation. The forecasted lifetime is used as a yard stick to witness the drivers’ targeted lifetime. In our presentation we will demonstrate the tool. In this paper, we describe details of how ERT calculates failure rates. We will also present the comparison between field performance and calculated values of our electronic drivers.