Striking Distance Research Articles

Life on the Wellington Fault: Managing Geological Collections and Earthquake Risk

GNS Science is home to New Zealand’s national rock, mineral and fossil collections. The National Petrology Reference Collection (NPRC) is a ‘nationally significant’ collection of rocks and minerals from on- and off-shore New Zealand, Antarctica and the rest of the world. The National Paleontological Collection (NPC) is another nationally significant collection; of fossil material from New Zealand, the South West Pacific region and Antarctica, with some overseas additions. Their status as nationally significant collections mean that GNS Science is contracted by the New Zealand Government to provide long-term collection management. Collectively, the NPC and NPRC constitute more than 200,000 samples, dating from the earliest days of New Zealand geology exploration in the late 1800s. The collections continue to grow by hundreds to thousands of samples per year, and are loaned nationally and internationally for scientific research. They are by far the largest collections of fossils, rocks and minerals housed in New Zealand, and are important earth science archives for the entire Zealandian Southern Ocean region. The collections are housed on-site at GNS Science in Lower Hutt, a few hundred meters from the surface trace of the Wellington Fault and within striking distance of other active faults that could generate major earthquakes. Best estimates suggest that the Wellington Region has an average return time of about 150 years for very strong or extreme ground shaking. Such proximity to this significant, active hazard means that steps must be taken to ensure the long-term security and integrity of the collections in the event of earthquake shaking, as well as other natural and non-natural disasters. To that end, the collection managers have written and implemented disaster mitigation, preparedness and recovery plans for the National Petrology Reference Collection and National Paleontological Collection. Here we define the earthquake hazard posed by the Wellington Fault, assess the risk to the collections, and present steps taken to manage that risk.

Lightning strokes and its effects on historical monuments, heritage properties and important landmarks a detailed perspective of traditional and scientific methods of lightning protection systems

Lightning is one of the inevitable disastrous natural phenomena which present serious threat to tall structures including ancient monuments and electrical systems. Though researchers have carried out a wide gamut of research studies to analyze the extent of damage due to direct lightning strikes on important buildings and structures, the focus of this research is on understanding the effects of lightning on tall structures of historical importance and landmark monuments of significance. In this context, different types of Lightning Protection Systems (LPS) are being used to protect tall structures from lightning flashes. However, several complexities related to the appropriate choice of LPS continue to confront researchers since characteristics of lightning such as stroke current, striking distance, return stroke modelling, geometry of the structure etc. pose considerable challenges. This research study presents a detailed chronological overview of lightning strikes on ancient structures, cause and effects, review on LPS strategies along with its impacts on tall structures, historical monuments and landmarks. In addition, a detailed analysis based on a specific case study of a typical historical monument is carried out to ascertain the critical significance of the stipulated zone of protection essential for historical monuments and various risks involved during implementation.

Predatory strategies and behaviours in cephalopods are altered by elevated CO2

There is increasing evidence that projected near-future carbon dioxide (CO2 ) levels can alter predator avoidance behaviour in marine invertebrates, yet little is known about the possible effects on predatory behaviours. Here we tested the effects of elevated CO2 on the predatory behaviours of two ecologically distinct cephalopod species, the pygmy squid, Idiosepius pygmaeus, and the bigfin reef squid, Sepioteuthis lessoniana. Both species exhibited an increased latency to attack and altered body pattern choice during the attack sequence at elevated CO2 . I.pygmaeus also exhibited a 20% decrease in predation rate, an increased striking distance, and reduced preference for attacking the posterior end of prey at elevated CO2 . Elevated CO2 increased activity levels of S.lessoniana comparable to those previously shown in I.pygmaeus, which could adversely affect their energy budget and increase their potential to be preyed upon. The effects of elevated CO2 on predatory behaviours, predation strategies and activity levels of cephalopods reported here could have far-reaching consequences in marine ecosystems due to the ecological importance of cephalopods in the marine food web.

Striking Distance Determined From High‐Speed Videos and Measured Currents in Negative Cloud‐to‐Ground Lightning

AbstractFirst and subsequent return strokes' striking distances (SDs) were determined for negative cloud‐to‐ground flashes from high‐speed videos exhibiting the development of positive and negative leaders and the pre–return stroke phase of currents measured along a short tower. In order to improve the results, a new criterion was used for the initiation and propagation of the sustained upward connecting leader, consisting of a 4 A continuous current threshold. An advanced approach developed from the combined use of this criterion and a reverse propagation procedure, which considers the calculated propagation speeds of the leaders, was applied and revealed that SDs determined solely from the first video frame showing the upward leader can be significantly underestimated. An original approach was proposed for a rough estimate of first strokes' SD using solely records of current. This approach combines the 4 A criterion and a representative composite three‐dimensional propagation speed of 0.34 × 106 m/s for the leaders in the last 300 m propagated distance. SDs determined under this approach showed to be consistent with those of the advanced procedure. This approach was applied to determine the SD of 17 first return strokes of negative flashes measured at MCS, covering a wide peak‐current range, from 18 to 153 kA. The estimated SDs exhibit very high dispersion and reveal great differences in relation to the SDs estimated for subsequent return strokes and strokes in triggered lightning.

LPM-Based Shielding Performance Analysis of High-Voltage Substations Against Direct Lightning Strokes

The leader progression model (LPM) is employed to investigate the shielding system performance of high-voltage substations against direct lightning strokes in the presence of substation instruments. The substation is simulated in detail for high accurate calculation of the shielding failure rate. Almost all of the apparatuses are modeled as fictitious charges in the stepwise simulations of LPM. The charge simulation method is used for finding the electrical field during the lightning movement. The probability of upward leader propagation is considered from all apparatuses. For more practical simulation, the environmental conditions are also included in simulations. The investigations are implemented on a test case and a practical high-voltage substation. The results are compared to those of the electrogeometric model. It is very likely that the results of this paper better simulate reality because lots of parameters have been taken into account. The results reveal that the presence of substation instruments increases the striking distance and the SF since they attract the lightning moving down near the substation.

Aqueous Li-Ion Batteries: Now in Striking Distance

In the inaugural issue of Joule , Chunsheng Wang, Kang Xu, and colleagues demonstrate a groundbreaking advance in Li-ion battery electrolytes with their design and demonstration of 4 V aqueous Li-ion batteries, which in theory could eliminate several environmental, safety, and manufacturing restrictions and concerns raised by non-aqueous electrolytes.

An Electro-Geometric Model for Lightning Shielding of Multiple Wind Turbines

Wind turbine blades being struck by lightning is one of the most urgent problems facing wind farms. In order to reduce the probability of lightning accidents on wind farms, this paper presents a new electro-geometric model for multiple turbines. In this new model, based on the physical model of lightning leader development, the striking distance range of the blade tip receptor is calculated, taking into account the influence of the charged particles around the blade. Lightning shielding amongst multiple turbines is provided in combination with the traditional electro-geometric model, and a criterion formula is obtained for mutual shielding for multiple turbines. The influence of environmental factors, such as temperature, atmospheric pressure, air humidity, and altitude, on lightning shielding on large-scale wind farms is also analyzed by studying the lightning shielding distance between wind turbines. The calculation shows that the larger the relative air density and the absolute humidity, and the lower the altitude, and the larger the lightning shielding distance between wind turbines. The method proposed in this paper provides a theoretical basis for the lightning protection on wind farms under different environmental conditions.

Lightning attachment process to common buildings

AbstractThe physical mechanism of lightning attachment to grounded structures is one of the most important issues in lightning physics research, and it is the basis for the design of the lightning protection systems. Most of what is known about the attachment process comes from leader propagation models that are mostly based on laboratory observations of long electrical discharges or from observations of lightning attachment to tall structures. In this paper we use high‐speed videos to analyze the attachment process of downward lightning flashes to an ordinary residential building. For the first time, we present characteristics of the attachment process to common structures that are present in almost every city (in this case, two buildings under 60 m in São Paulo City, Brazil). Parameters like striking distance and connecting leaders speed, largely used in lightning attachment models and in lightning protection standards, are revealed in this work.

An Application of Fractal-Based Lightning for SFR Calculation of High Voltage Substations

Objectives: To simulate the lightning more close to reality and investigate the performance of the lightning protection system of high voltage substation. Methods/Statistical Analysis: The method which is used for the system analysis is a new fractal-based model of simulated lightning by which the zigzag movement of lightning downward leader as well as branching nature is simulated. A new charge distribution is proposed for branched lightning channel. In addition, the branch fading during the lightning downward movement is also simulated in order to simulate the lightning more close to the reality. Findings: The results of the simulated lightning using the proposed method show that the proposed fractal method simulates the lightning close to the reality. The striking distances of a transmission line structure for different lightning return stroke currents are obtained by the proposed method and compared to those of Electrogeometric Model (EGM) and Leader Progression Model (LPM). The results show that how the proposed method obtains a wide range of possible results statistically. The lightning shielding system performance of a practical high voltage substation is investigated based on the proposed model in two different scenarios by which the effect of substation instruments on the lightning protection system is investigated. The results reveal that the presence of the substation instruments completely affects the shielding system performance. Using the propose method, the random behavior of the lightning is well modeled and the shielding failure of the protection system is investigated in a statistical manner. The obtained results are compared to those of EGM, and LPM. The results are discussed and superiority of the proposed simulated lightning model is concluded. Application/ Improvements: The proposed method simulates the different features of the lightning including 1- branching nature, 2- zigzag movement, 3- random behavior, 4- branch fading, 5- branched charge distribution.

A Concept for Striking Range Improvement of the GROM/PIORUN Man-Portable Air-Defence System

This paper presents a concept for striking distance performance improvement of the GROM/PIORUN Man-Portable Air-Defence System rocket missiles by increasing the rated diameter of the rocket missile propulsion system and its fuel charge weight. A mathematical and physical model of the GROM rocket missile was designed and its enhanced propulsion system was simulated in a computer environment. The computer simulation results were displayed on plot charts.

Improved Electrogeometric Model Suitable for EHV and UHV Transmission Lines Developed through Breakdown Testing for Long Air Gaps

As a type of engineering model used for solving lightning-shielding problems, the electrogeometric model has been widely used for assessing lightning-shielding failure in high-voltage and extra-high-voltage transmission lines. However, with the increase of voltage levels in ultra-high-voltage lines and the growth of the air gap, the results previously yielded by the electrogeometric model are no longer consistent with those observed. Therefore, this study corrected the equation for the relationship between lightning current and striking distance, by using data on a negative polarity 50% discharge voltage from the rod-rod gap −20/2500 μs switching impulse test wherein an air gap of up to 10 m was first tested. Subsequently, the return stroke velocity distribution observed by Idone was newly applied. In addition, the correction factor for the ground was corrected in this study. Thus, an improved electrogeometric model for application in EHV and UHV transmission lines is proposed in this paper. By employing the improved electrogeometric model to calculate the frequency of lightning strikes of 500 and 1000 kV transmission lines in Japan and a 1000 kV transmission line in China, we found that the results calculated using the improved electrogeometric model were closer to the actual observations in Japan than was the original electrogeometric model. The improved electrogeometric model provides a more reliable foundation for lightning-shielding design of extra-high-voltage and ultra-high-voltage transmission lines.

Estimation of the shielding performance of transmission lines considering effects of landform, lightning polarity and stroke angle

Lightning is the main cause of transmission system outages, affecting reliability of power supply and resulting in economic losses. Shielding failure is an important issue in addressing the lightning performance of overhead transmission lines. In this paper an improved method based on the electro-geometric model is proposed to evaluate the shielding failure flashover rate (SFFOR) of transmission lines, considering the influences of landform, lightning polarity and stroke angle. In the improved method, the striking distances to phase conductors, shield wires and ground are properly differentiated by using recent equations developed to take into account other factors not only magnitude of lightning strokes. These factors include height of wires as well as lightning polarity. To reflect the effects of changes in terrain and height of wires on SFFOR, a method for identifying the topography and the relative position among the wires and ground is proposed. A 400-kV double-circuit transmission line section in complex terrain area was taken as example, and the results show that this method can reflect changes of the SFFOR along the span and can be useful to figure out which towers are easy to be struck by lightning along the entire transmission line. This research is helpful for the design and operation of overhead transmission lines.

Habitat choice and hunting behaviour of the alligator pipefish, Syngnathoides biaculeatus, in captivity

The alligator pipefish, Syngnathoides biaculeatus, is a cryptic species commonly found in seagrass meadows. The fish is shy and slow, and it is unknown how the predaceous fish hunts its mobile prey. This study determined its feeding behaviour in an artificial setting of open and vegetated area in an aquarium. Fish behaviour was observed and studied during the early feeding and post-feeding event. The behaviour of 14 pipefish was individually recorded for a duration of 10 min each for each event, and recorded events were replayed and scored using an event recorder. Fish behaviour and duration were scored following an ethogram based on categories of habitat preference (vegetated/open), body orientation (horizontal/vertical), grasping behaviour (using prehensile tail) and hunting approach (horizontal front/vertical front/horizontal rear/vertical rear). Results showed a greater habitat preference for the vegetated area compared to the open area for both sexes. The pipefish also displayed side rolls resembling the moving blade of seagrass in its natural habitat. There was no orientation preference in either sex, nor between early feeding and post-feeding stages. Non-grasping behaviour was favoured after introduction into the tank and during early feeding by both sexes, while the grasping behaviour was favoured during post-feeding. The pipefish adopted a target-locking strategy while mimicking the seagrass movement as it approached its prey. The ambush strategy was adopted while waiting for its prey to approach it within striking distance. Each pipefish showed four hunting approaches, but there was no concordance on the preferred hunting approach among them. The feeding behaviour of the alligator pipefish incorporating stealth and camouflage appears to show an obligatory dependence on seagrass meadows for its survival.

Perception of Affordances for Striking Regulates Interpersonal Distance Maneuvers of Intermediate and Expert Players in Kendo Matches

ABSTRACTIn daily life and in many sports, people must adjust interpersonal distance between themselves and others based on task constraints and goals. For example, in martial arts such as boxing and kendo, players must adjust interpersonal distance before starting or defending strikes. However, it is not clear what players perceive and how players use this perceptual information to maneuver interpersonal distance and start strikes during real matches. We investigated players' perception of affordances and the criteria for perception and behaviors, and how these change with expertise, using real kendo matches as a one-on-one opponent task. Players perceived affordances for striking for themselves and for their opponent based on subtle interpersonal distance changes and clearly switched stepping forward and backward. In addition, players perceived affordances for strike success and entered closer interpersonal distance than the possible striking distance to increase their own striking ability and exited the closer distance to decrease their opponent's striking ability, respectively. Furthermore, expert players stayed in and moved into the critical interpersonal distance more frequently than intermediate players did. Our research indicates a relationship between action-scaled affordance perception of and maneuvers associated with interpersonal distance in one-on-one situations that occur in daily life and in many sports.

Dynamic striking distance and electrical geometrical model of wind turbine blades based on lightning physics

Dynamic striking distance and electrical geometrical model of wind turbine blades based on lightning physics

Estimation of the electric fields and dielectric breakdown in non-conductive wind turbine blades subjected to a lightning stepped leader

In this paper, the electric fields in the wind turbine blades due to the lightning stepped leader are studied, and the dielectric breakdown is assessed. The developed finite element analysis (FEA) includes the full length of the leader and enables one to incorporate various uniform and non-uniform charge density models. The lightning striking distance is calculated using the rolling sphere method. The electric field in a horizontal axis wind turbine with three blades representing Sandia 100 m All-glass Baseline Wind Turbine Blades (SNL 100-00) at three different lightning protection levels (LPL) is computed and compared to the dielectric breakdown strength of the blades. The dielectric breakdown strength of the blades is evaluated based on the experimental data. The results show that the tip region of the blade is the most vulnerable to the dielectric breakdown with the safety factor as low as 1.32 at LPL I. Copyright © 2016 John Wiley & Sons, Ltd.

Editor's Re: Marks

Editor's Re: Marks

Simulation of the Lightning Back-Flashover for Medium Voltage Distribution Network

Lightning strikes represent a considerable cause of short interruptions in electrical overhead line networks. The over voltages caused by lightning cannot be avoided but their influence can be limited by appropriate over voltage protection. This paper presents analysis study on some factors affecting the back flashover of Egyptian 66 kV distribution lines using Alternative Transient Program (ATP). The study includes the modeling of 66 kV distribution lines, the effects of magnitude and the front and tail times of lightning wave on the back flashover voltages, the effects of the striking distance, and the using of counterpoise wires on the back flashover on the 66 kV line towers. In this paper the 66 kV lines sag is neglected and the soil ionization by the flow of the stroke current is considered.

Politicians must commit to affordable homes.

The cost of housing is an issue for most of us, but nursing staff have been among those hit hardest by soaring property prices. Finding affordable accommodation within striking distance of work is a challenge in many parts of the UK, not only hotspots such as London and south east England that are known to be expensive.

New Simulation Method of Flashover Rate by Connection of EMTP and MATLAB

Because of the random characteristics of lightning, the Monte Carlo method is applied to estimate the flashover rate due to lightning, however, the simulations using previous methods are difficult to both beginner and expert in power corporations. Therefore, this paper proposes the new and easy method to simulate the flashover rate by connection of electromagnetic transients program (EMTP) and MATLAB. The magnitude of a lightning strike is based on a curve measured in the field, while the classification of direct and indirect lightning depends on the striking distance. In a Korean distribution system, the flashover rate induced by lightning is simulated using proposed method. Simulations of the footing resistance according to the existence of an overhead ground wire (OHGW) are performed and the simulation results are discussed. The simulation results are compared with findings obtained with the IEEE Flash 2.0 program.